# macros

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This module contains the interface to the compiler's abstract syntax tree (AST). Macros operate on this tree.

See also:

- macros tutorial
- macros section in Nim manual

# The AST in Nim

This section describes how the AST is modelled with Nim's type system. The AST consists of nodes (`NimNode`) with a variable number of children. Each node has a field named `kind` which describes what the node contains:

    type
      NimNodeKind = enum     ## kind of a node; only explanatory
        nnkNone,             ## invalid node kind
        nnkEmpty,            ## empty node
        nnkIdent,            ## node contains an identifier
        nnkIntLit,           ## node contains an int literal (example: 10)
        nnkStrLit,           ## node contains a string literal (example: "abc")
        nnkNilLit,           ## node contains a nil literal (example: nil)
        nnkCaseStmt,         ## node represents a case statement
        ...                  ## many more

      NimNode = ref NimNodeObj
      NimNodeObj = object
        case kind: NimNodeKind           ## the node's kind
        of nnkNone, nnkEmpty, nnkNilLit:
          discard                        ## node contains no additional fields
        of nnkCharLit..nnkUInt64Lit:
          intVal: BiggestInt             ## the int literal
        of nnkFloatLit..nnkFloat64Lit:
          floatVal: BiggestFloat         ## the float literal
        of nnkStrLit..nnkTripleStrLit, nnkCommentStmt, nnkIdent, nnkSym:
          strVal: string                 ## the string literal
        else:
          sons: seq[NimNode]             ## the node's sons (or children)

For the `NimNode` type, the `[]` operator has been overloaded: `n[i]` is `n`'s `i`-th child.

To specify the AST for the different Nim constructs, the notation `nodekind(son1, son2, ...)` or `nodekind(value)` or `nodekind(field=value)` is used.

Some child may be missing. A missing child is a node of kind `nnkEmpty`; a child can never be nil.

# Leaf nodes/Atoms

A leaf of the AST often corresponds to a terminal symbol in the concrete syntax. Note that the default `float` in Nim maps to `float64` such that the default AST for a float is `nnkFloat64Lit` as below.

Nim expression | Corresponding AST
--- | ---
`42` | `nnkIntLit(intVal = 42)`
`42'i8` | `nnkInt8Lit(intVal = 42)`
`42'i16` | `nnkInt16Lit(intVal = 42)`
`42'i32` | `nnkInt32Lit(intVal = 42)`
`42'i64` | `nnkInt64Lit(intVal = 42)`
`42'u8` | `nnkUInt8Lit(intVal = 42)`
`42'u16` | `nnkUInt16Lit(intVal = 42)`
`42'u32` | `nnkUInt32Lit(intVal = 42)`
`42'u64` | `nnkUInt64Lit(intVal = 42)`
`42.0` | `nnkFloat64Lit(floatVal = 42.0)`
`42.0'f32` | `nnkFloat32Lit(floatVal = 42.0)`
`42.0'f64` | `nnkFloat64Lit(floatVal = 42.0)`
`"abc"` | `nnkStrLit(strVal = "abc")`
`r"abc"` | `nnkRStrLit(strVal = "abc")`
`"""abc"""` | `nnkTripleStrLit(strVal = "abc")`
`' '` | `nnkCharLit(intVal = 32)`
`nil` | `nnkNilLit()`
`myIdentifier` | `nnkIdent(strVal = "myIdentifier")`
`myIdentifier` | after lookup pass: `nnkSym(strVal = "myIdentifier", ...)`

Identifiers are `nnkIdent` nodes. After the name lookup pass these nodes get transferred into `nnkSym` nodes.

# Calls/expressions

## Command call

Concrete syntax:

    echo "abc", "xyz"

AST:

    nnkCommand(
      nnkIdent("echo"),
      nnkStrLit("abc"),
      nnkStrLit("xyz")
    )

## Call with `()`

Concrete syntax:

    echo("abc", "xyz")

AST:

    nnkCall(
      nnkIdent("echo"),
      nnkStrLit("abc"),
      nnkStrLit("xyz")
    )

## Infix operator call

Concrete syntax:

    "abc" & "xyz"

AST:

    nnkInfix(
      nnkIdent("&"),
      nnkStrLit("abc"),
      nnkStrLit("xyz")
    )

Note that with multiple infix operators, the command is parsed by operator precedence.

Concrete syntax:

    5 + 3 * 4

AST:

    nnkInfix(
      nnkIdent("+"),
      nnkIntLit(5),
      nnkInfix(
        nnkIdent("*"),
        nnkIntLit(3),
        nnkIntLit(4)
      )
    )

As a side note, if you choose to use infix operators in a prefix form, the AST behaves as a parenthetical function call with `nnkAccQuoted`, as follows:

Concrete syntax:

    `+`(3, 4)

AST:

    nnkCall(
      nnkAccQuoted(
        nnkIdent("+")
      ),
      nnkIntLit(3),
      nnkIntLit(4)
    )

## Prefix operator call

Concrete syntax:

    ? "xyz"

AST:

    nnkPrefix(
      nnkIdent("?"),
      nnkStrLit("abc")
    )

## Postfix operator call

Note: There are no postfix operators in Nim. However, the `nnkPostfix` node is used for the asterisk export marker `*`:

Concrete syntax:

    identifier*

AST:

    nnkPostfix(
      nnkIdent("*"),
      nnkIdent("identifier")
    )

## Call with named arguments

Concrete syntax:

    writeLine(file=stdout, "hallo")

AST:

    nnkCall(
      nnkIdent("writeLine"),
      nnkExprEqExpr(
        nnkIdent("file"),
        nnkIdent("stdout")
      ),
      nnkStrLit("hallo")
    )

## Call with raw string literal

This is used, for example, in the `bindSym` examples here and with `re"some regexp"` in the regular expression module.

Concrete syntax:

    echo"abc"

AST:

    nnkCallStrLit(
      nnkIdent("echo"),
      nnkRStrLit("hello")
    )

## Dereference operator `[]`

Concrete syntax:

    x[]

AST:

    nnkDerefExpr(nnkIdent("x"))

## Addr operator

Concrete syntax:

    addr(x)

AST:

    nnkAddr(nnkIdent("x"))

## Cast operator

Concrete syntax:

    cast[T](x)

AST:

    nnkCast(nnkIdent("T"), nnkIdent("x"))

## Object access operator `.`

Concrete syntax:

    x.y

AST:

    nnkDotExpr(nnkIdent("x"), nnkIdent("y"))

If you use Nim's flexible calling syntax (as in `x.len()`), the result is the same as above but wrapped in an `nnkCall`.

## Array access operator `[]`

Concrete syntax:

    x[y]

AST:

    nnkBracketExpr(nnkIdent("x"), nnkIdent("y"))

## Parentheses

Parentheses for affecting operator precedence or tuple construction are built with the `nnkPar` node.

Concrete syntax:

    (1, 2, (3))

AST:

    nnkPar(nnkIntLit(1), nnkIntLit(2), nnkPar(nnkIntLit(3)))

## Curly braces

Curly braces are used as the set constructor.

Concrete syntax:

    {1, 2, 3}

AST:

    nnkCurly(nnkIntLit(1), nnkIntLit(2), nnkIntLit(3))

When used as a table constructor, the syntax is different.

Concrete syntax:

    {a: 3, b: 5}

AST:

    nnkTableConstr(
      nnkExprColonExpr(nnkIdent("a"), nnkIntLit(3)),
      nnkExprColonExpr(nnkIdent("b"), nnkIntLit(5))
    )

## Brackets

Brackets are used as the array constructor.

Concrete syntax:

    [1, 2, 3]

AST:

    nnkBracket(nnkIntLit(1), nnkIntLit(2), nnkIntLit(3))

## Ranges

Ranges occur in set constructors, case statement branches, or array slices. Internally, the node kind `nnkRange` is used, but when constructing the AST, construction with `..` as an infix operator should be used instead.

Concrete syntax:

    1..3

AST:

    nnkInfix(
      nnkIdent(".."),
      nnkIntLit(1),
      nnkIntLit(3)
    )

Example code:

    macro genRepeatEcho(): stmt =
      result = newNimNode(nnkStmtList)

      var forStmt = newNimNode(nnkForStmt) # generate a for statement
      forStmt.add(ident("i")) # use the variable `i` for iteration

      var rangeDef = newNimNode(nnkInfix).add(
        ident("..")).add(
        newIntLitNode(3),newIntLitNode(5)) # iterate over the range 3..5

      forStmt.add(rangeDef)
      forStmt.add(newCall(ident("echo"), newIntLitNode(3))) # meat of the loop
      result.add(forStmt)

    genRepeatEcho() # gives:
                    # 3
                    # 3
                    # 3

## If expression

The representation of the `if` expression is subtle, but easy to traverse.

Concrete syntax:

    if cond1: expr1 elif cond2: expr2 else: expr3

AST:

    nnkIfExpr(
      nnkElifExpr(cond1, expr1),
      nnkElifExpr(cond2, expr2),
      nnkElseExpr(expr3)
    )

## Documentation Comments

Double-hash (`##`) comments in the code actually have their own format, using `strVal` to get and set the comment text. Single-hash (`#`) comments are ignored.

Concrete syntax:

    ## This is a comment
    ## This is part of the first comment
    stmt1
    ## Yet another

AST:

    nnkCommentStmt() # only appears once for the first two lines!
    stmt1
    nnkCommentStmt() # another nnkCommentStmt because there is another comment
                     # (separate from the first)

## Pragmas

One of Nim's cool features is pragmas, which allow fine-tuning of various aspects of the language. They come in all types, such as adorning procs and objects, but the standalone `emit` pragma shows the basics with the AST.

Concrete syntax:

    {.emit: "#include <stdio.h>".}

AST:

    nnkPragma(
      nnkExprColonExpr(
        nnkIdent("emit"),
        nnkStrLit("#include <stdio.h>") # the "argument"
      )
    )

As many `nnkIdent` appear as there are pragmas between `{..}`. Note that the declaration of new pragmas is essentially the same:

Concrete syntax:

    {.pragma: cdeclRename, cdecl.}

AST:

    nnkPragma(
      nnkExprColonExpr(
        nnkIdent("pragma"), # this is always first when declaring a new pragma
        nnkIdent("cdeclRename") # the name of the pragma
      ),
      nnkIdent("cdecl")
    )

# Statements

## If statement

The representation of the if statement is subtle, but easy to traverse. If there is no `else` branch, no `nnkElse` child exists.

Concrete syntax:

    if cond1:
      stmt1
    elif cond2:
      stmt2
    elif cond3:
      stmt3
    else:
      stmt4

AST:

    nnkIfStmt(
      nnkElifBranch(cond1, stmt1),
      nnkElifBranch(cond2, stmt2),
      nnkElifBranch(cond3, stmt3),
      nnkElse(stmt4)
    )

## When statement

Like the `if` statement, but the root has the kind `nnkWhenStmt`.

## Assignment

Concrete syntax:

    x = 42

AST:

    nnkAsgn(nnkIdent("x"), nnkIntLit(42))

This is not the syntax for assignment when combined with `var`, `let`, or `const`.

## Statement list

Concrete syntax:

    stmt1
    stmt2
    stmt3

AST:

    nnkStmtList(stmt1, stmt2, stmt3)

## Case statement

Concrete syntax:

    case expr1
    of expr2, expr3..expr4:
      stmt1
    of expr5:
      stmt2
    elif cond1:
      stmt3
    else:
      stmt4

AST:

    nnkCaseStmt(
      expr1,
      nnkOfBranch(expr2, nnkRange(expr3, expr4), stmt1),
      nnkOfBranch(expr5, stmt2),
      nnkElifBranch(cond1, stmt3),
      nnkElse(stmt4)
    )

The `nnkElifBranch` and `nnkElse` parts may be missing.

## While statement

Concrete syntax:

    while expr1:
      stmt1

AST:

    nnkWhileStmt(expr1, stmt1)

## For statement

Concrete syntax:

    for ident1, ident2 in expr1:
      stmt1

AST:

    nnkForStmt(ident1, ident2, expr1, stmt1)

## Try statement

Concrete syntax:

    try:
      stmt1
    except e1, e2:
      stmt2
    except e3:
      stmt3
    except:
      stmt4
    finally:
      stmt5

AST:

    nnkTryStmt(
      stmt1,
      nnkExceptBranch(e1, e2, stmt2),
      nnkExceptBranch(e3, stmt3),
      nnkExceptBranch(stmt4),
      nnkFinally(stmt5)
    )

## Return statement

Concrete syntax:

    return expr1

AST:

    nnkReturnStmt(expr1)

## Yield statement

Like `return`, but with `nnkYieldStmt` kind.

    nnkYieldStmt(expr1)

## Discard statement

Like `return`, but with `nnkDiscardStmt` kind.

    nnkDiscardStmt(expr1)

## Continue statement

Concrete syntax:

    continue

AST:

    nnkContinueStmt()

## Break statement

Concrete syntax:

    break otherLocation

AST:

    nnkBreakStmt(nnkIdent("otherLocation"))

If `break` is used without a jump-to location, `nnkEmpty` replaces `nnkIdent`.

## Block statement

Concrete syntax:

    block name:

AST:

    nnkBlockStmt(nnkIdent("name"), nnkStmtList(...))

A `block` doesn't need an name, in which case `nnkEmpty` is used.

## Asm statement

Concrete syntax:

    asm """
      some asm
    """

AST:

    nnkAsmStmt(
      nnkEmpty(), # for pragmas
      nnkTripleStrLit("some asm"),
    )

## Import section

Nim's `import` statement actually takes different variations depending on what keywords are present. Let's start with the simplest form.

Concrete syntax:

    import math

AST:

    nnkImportStmt(nnkIdent("math"))

With `except`, we get `nnkImportExceptStmt`.

Concrete syntax:

    import math except pow

AST:

    nnkImportExceptStmt(nnkIdent("math"),nnkIdent("pow"))

Note that `import math as m` does not use a different node; rather, we use `nnkImportStmt` with `as` as an infix operator.

Concrete syntax:

    import strutils as su

AST:

    nnkImportStmt(
      nnkInfix(
        nnkIdent("as"),
        nnkIdent("strutils"),
        nnkIdent("su")
      )
    )

## From statement

If we use `from ... import`, the result is different, too.

Concrete syntax:

    from math import pow

AST:

    nnkFromStmt(nnkIdent("math"), nnkIdent("pow"))

Using `from math as m import pow` works identically to the `as` modifier with the `import` statement, but wrapped in `nnkFromStmt`.

## Export statement

When you are making an imported module accessible by modules that import yours, the `export` syntax is pretty straightforward.

Concrete syntax:

    export unsigned

AST:

    nnkExportStmt(nnkIdent("unsigned"))

Similar to the `import` statement, the AST is different for `export ... except`.

Concrete syntax:

    export math except pow # we're going to implement our own exponentiation

AST:

    nnkExportExceptStmt(nnkIdent("math"),nnkIdent("pow"))

## Include statement

Like a plain `import` statement but with `nnkIncludeStmt`.

Concrete syntax:

    include blocks

AST:

    nnkIncludeStmt(nnkIdent("blocks"))

## Var section

Concrete syntax:

    var a = 3

AST:

    nnkVarSection(
      nnkIdentDefs(
        nnkIdent("a"),
        nnkEmpty(), # or nnkIdent(...) if the variable declares the type
        nnkIntLit(3),
      )
    )

Note that either the second or third (or both) parameters above must exist, as the compiler needs to know the type somehow (which it can infer from the given assignment).

This is not the same AST for all uses of `var`. See Procedure declaration for details.

## Let section

This is equivalent to `var`, but with `nnkLetSection` rather than `nnkVarSection`.

Concrete syntax:

    let a = 3

AST:

    nnkLetSection(
      nnkIdentDefs(
        nnkIdent("a"),
        nnkEmpty(), # or nnkIdent(...) for the type
        nnkIntLit(3),
      )
    )

## Const section

Concrete syntax:

    const a = 3

AST:

    nnkConstSection(
      nnkConstDef( # not nnkConstDefs!
        nnkIdent("a"),
        nnkEmpty(), # or nnkIdent(...) if the variable declares the type
        nnkIntLit(3), # required in a const declaration!
      )
    )

## Type section

Starting with the simplest case, a `type` section appears much like `var` and `const`.

Concrete syntax:

    type A = int

AST:

    nnkTypeSection(
      nnkTypeDef(
        nnkIdent("A"),
        nnkEmpty(),
        nnkIdent("int")
      )
    )

Declaring `distinct` types is similar, with the last `nnkIdent` wrapped in `nnkDistinctTy`.

Concrete syntax:

    type MyInt = distinct int

AST:

    # ...
    nnkTypeDef(
      nnkIdent("MyInt"),
      nnkEmpty(),
      nnkDistinctTy(
        nnkIdent("int")
      )
    )

If a type section uses generic parameters, they are treated here:

Concrete syntax:

    type A[T] = expr1

AST:

    nnkTypeSection(
      nnkTypeDef(
        nnkIdent("A"),
        nnkGenericParams(
          nnkIdentDefs(
            nnkIdent("T"),
            nnkEmpty(), # if the type is declared with options, like
                        # ``[T: SomeInteger]``, they are given here
            nnkEmpty(),
          )
        )
        expr1,
      )
    )

Note that not all `nnkTypeDef` utilize `nnkIdent` as their their parameter. One of the most common uses of type declarations is to work with objects.

Concrete syntax:

    type IO = object of RootObj

AST:

    # ...
    nnkTypeDef(
      nnkIdent("IO"),
      nnkEmpty(),
      nnkObjectTy(
        nnkEmpty(), # no pragmas here
        nnkOfInherit(
          nnkIdent("RootObj") # inherits from RootObj
        )
        nnkEmpty()
      )
    )

Nim's object syntax is rich. Let's take a look at an involved example in its entirety to see some of the complexities.

Concrete syntax:

    type Obj[T] = object {.inheritable.}
      name: string
      case isFat: bool
      of true:
        m: array[100_000, T]
      of false:
        m: array[10, T]

AST:

    # ...
    nnkObjectTy(
      nnkPragma(
        nnkIdent("inheritable")
      ),
      nnkEmpty(),
      nnkRecList( # list of object parameters
        nnkIdentDefs(
          nnkIdent("name"),
          nnkIdent("string"),
          nnkEmpty()
        ),
        nnkRecCase( # case statement within object (not nnkCaseStmt)
          nnkIdentDefs(
            nnkIdent("isFat"),
            nnkIdent("bool"),
            nnkEmpty()
          ),
          nnkOfBranch(
            nnkIdent("true"),
            nnkRecList( # again, a list of object parameters
              nnkIdentDefs(
                nnkIdent("m"),
                nnkBracketExpr(
                  nnkIdent("array"),
                  nnkIntLit(100000),
                  nnkIdent("T")
                ),
                nnkEmpty()
            )
          ),
          nnkOfBranch(
            nnkIdent("false"),
            nnkRecList(
              nnkIdentDefs(
                nnkIdent("m"),
                nnkBracketExpr(
                  nnkIdent("array"),
                  nnkIntLit(10),
                  nnkIdent("T")
                ),
                nnkEmpty()
              )
            )
          )
        )
      )
    )

Using an `enum` is similar to using an `object`.

Concrete syntax:

    type X = enum
      First

AST:

    # ...
    nnkEnumTy(
      nnkEmpty(),
      nnkIdent("First") # you need at least one nnkIdent or the compiler complains
    )

The usage of `concept` (experimental) is similar to objects.

Concrete syntax:

    type Con = concept x,y,z
      (x & y & z) is string

AST:

    # ...
    nnkTypeClassTy( # note this isn't nnkConceptTy!
      nnkArglist(
        # ... idents for x, y, z
      )
      # ...
    )

Static types, like `static[int]`, use `nnkIdent` wrapped in `nnkStaticTy`.

Concrete syntax:

    type A[T: static[int]] = object

AST:

    # ... within nnkGenericParams
    nnkIdentDefs(
      nnkIdent("T"),
      nnkStaticTy(
        nnkIdent("int")
      ),
      nnkEmpty()
    )
    # ...

In general, declaring types mirrors this syntax (i.e., `nnkStaticTy` for `static`, etc.). Examples follow (exceptions marked by `*`):

Nim type | Corresponding AST
--- | ---
`static` | `nnkStaticTy`
`tuple` | `nnkTupleTy`
`var` | `nnkVarTy`
`ptr` | `nnkPtrTy`
`ref` | `nnkRefTy`
`distinct` | `nnkDistinctTy`
`enum` | `nnkEnumTy`
`concept` | `nnkTypeClassTy`*
`array` | `nnkBracketExpr(nnkIdent("array"),...`*
`proc` | `nnkProcTy`
`iterator` | `nnkIteratorTy`
`object` | `nnkObjectTy`

Take special care when declaring types as `proc`. The behavior is similar to `Procedure declaration`, below, but does not treat `nnkGenericParams`. Generic parameters are treated in the type, not the `proc` itself.

Concrete syntax:

    type MyProc[T] = proc(x: T)

AST:

    # ...
    nnkTypeDef(
      nnkIdent("MyProc"),
      nnkGenericParams( # here, not with the proc
        # ...
      )
      nnkProcTy( # behaves like a procedure declaration from here on
        nnkFormalParams(
          # ...
        )
      )
    )

The same syntax applies to `iterator` (with `nnkIteratorTy`), but does not apply to `converter` or `template`.

## Mixin statement

Concrete syntax:

    mixin x

AST:

    nnkMixinStmt(nnkIdent("x"))

## Bind statement

Concrete syntax:

    bind x

AST:

    nnkBindStmt(nnkIdent("x"))

## Procedure declaration

Let's take a look at a procedure with a lot of interesting aspects to get a feel for how procedure calls are broken down.

Concrete syntax:

    proc hello*[T: SomeInteger](x: int = 3, y: float32): int {.inline.} = discard

AST:

    nnkProcDef(
      nnkPostfix(nnkIdent("*"), nnkIdent("hello")), # the exported proc name
      nnkEmpty(), # patterns for term rewriting in templates and macros (not procs)
      nnkGenericParams( # generic type parameters, like with type declaration
        nnkIdentDefs(
          nnkIdent("T"), nnkIdent("SomeInteger")
        )
      ),
      nnkFormalParams(
        nnkIdent("int"), # the first FormalParam is the return type. nnkEmpty() if there is none
        nnkIdentDefs(
          nnkIdent("x"),
          nnkIdent("int"), # type type (required for procs, not for templates)
          nnkIntLit(3) # a default value
        ),
        nnkIdentDefs(
          nnkIdent("y"),
          nnkIdent("float32"),
          nnkEmpty()
        )
      ),
      nnkPragma(nnkIdent("inline")),
      nnkEmpty(), # reserved slot for future use
      nnkStmtList(nnkDiscardStmt(nnkEmpty())) # the meat of the proc
    )

There is another consideration. Nim has flexible type identification for its procs. Even though `proc(a: int, b: int)` and `proc(a, b: int)` are equivalent in the code, the AST is a little different for the latter.

Concrete syntax:

    proc(a, b: int)

AST:

    # ...AST as above...
    nnkFormalParams(
      nnkEmpty(), # no return here
      nnkIdentDefs(
        nnkIdent("a"), # the first parameter
        nnkIdent("b"), # directly to the second parameter
        nnkIdent("int"), # their shared type identifier
        nnkEmpty(), # default value would go here
      )
    ),
    # ...

When a procedure uses the special `var` type return variable, the result is different from that of a var section.

Concrete syntax:

    proc hello(): var int

AST:

    # ...
    nnkFormalParams(
      nnkVarTy(
        nnkIdent("int")
      )
    )

## Iterator declaration

The syntax for iterators is similar to procs, but with `nnkIteratorDef` replacing `nnkProcDef`.

Concrete syntax:

    iterator nonsense[T](x: seq[T]): float {.closure.} = ...

AST:

    nnkIteratorDef(
      nnkIdent("nonsense"),
      nnkEmpty(),
      ...
    )

## Converter declaration

A converter is similar to a proc.

Concrete syntax:

    converter toBool(x: float): bool

AST:

    nnkConverterDef(
      nnkIdent("toBool"),
      # ...
    )

## Template declaration

Templates (as well as macros, as we'll see) have a slightly expanded AST when compared to procs and iterators. The reason for this is [term-rewriting macros](http://nim-lang.org/docs/manual.html#term-rewriting-macros). Notice the `nnkEmpty()` as the second argument to `nnkProcDef` and `nnkIteratorDef` above? That's where the term-rewriting macros go.

Concrete syntax:

    template optOpt{expr1}(a: int): int

AST:

    nnkTemplateDef(
      nnkIdent("optOpt"),
      nnkStmtList( # instead of nnkEmpty()
        expr1
      ),
      # follows like a proc or iterator
    )

If the template does not have types for its parameters, the type identifiers inside `nnkFormalParams` just becomes `nnkEmpty`.

## Macro declaration

Macros behave like templates, but `nnkTemplateDef` is replaced with `nnkMacroDef`.

# Special node kinds

There are several node kinds that are used for semantic checking or code generation. These are accessible from this module, but should not be used. Other node kinds are especially designed to make AST manipulations easier. These are explained here.

To be written.

# Types

    NimNodeKind = enum
      nnkNone, nnkEmpty, nnkIdent, nnkSym, nnkType, nnkCharLit, nnkIntLit, nnkInt8Lit,
      nnkInt16Lit, nnkInt32Lit, nnkInt64Lit, nnkUIntLit, nnkUInt8Lit, nnkUInt16Lit,
      nnkUInt32Lit, nnkUInt64Lit, nnkFloatLit, nnkFloat32Lit, nnkFloat64Lit,
      nnkFloat128Lit, nnkStrLit, nnkRStrLit, nnkTripleStrLit, nnkNilLit, nnkComesFrom,
      nnkDotCall, nnkCommand, nnkCall, nnkCallStrLit, nnkInfix, nnkPrefix, nnkPostfix,
      nnkHiddenCallConv, nnkExprEqExpr, nnkExprColonExpr, nnkIdentDefs, nnkVarTuple,
      nnkPar, nnkObjConstr, nnkCurly, nnkCurlyExpr, nnkBracket, nnkBracketExpr,
      nnkPragmaExpr, nnkRange, nnkDotExpr, nnkCheckedFieldExpr, nnkDerefExpr, nnkIfExpr,
      nnkElifExpr, nnkElseExpr, nnkLambda, nnkDo, nnkAccQuoted, nnkTableConstr, nnkBind,
      nnkClosedSymChoice, nnkOpenSymChoice, nnkHiddenStdConv, nnkHiddenSubConv, nnkConv,
      nnkCast, nnkStaticExpr, nnkAddr, nnkHiddenAddr, nnkHiddenDeref, nnkObjDownConv,
      nnkObjUpConv, nnkChckRangeF, nnkChckRange64, nnkChckRange, nnkStringToCString,
      nnkCStringToString, nnkAsgn, nnkFastAsgn, nnkGenericParams, nnkFormalParams,
      nnkOfInherit, nnkImportAs, nnkProcDef, nnkMethodDef, nnkConverterDef, nnkMacroDef,
      nnkTemplateDef, nnkIteratorDef, nnkOfBranch, nnkElifBranch, nnkExceptBranch,
      nnkElse, nnkAsmStmt, nnkPragma, nnkPragmaBlock, nnkIfStmt, nnkWhenStmt, nnkForStmt,
      nnkParForStmt, nnkWhileStmt, nnkCaseStmt, nnkTypeSection, nnkVarSection,
      nnkLetSection, nnkConstSection, nnkConstDef, nnkTypeDef, nnkYieldStmt, nnkDefer,
      nnkTryStmt, nnkFinally, nnkRaiseStmt, nnkReturnStmt, nnkBreakStmt, nnkContinueStmt,
      nnkBlockStmt, nnkStaticStmt, nnkDiscardStmt, nnkStmtList, nnkImportStmt,
      nnkImportExceptStmt, nnkExportStmt, nnkExportExceptStmt, nnkFromStmt,
      nnkIncludeStmt, nnkBindStmt, nnkMixinStmt, nnkUsingStmt, nnkCommentStmt,
      nnkStmtListExpr, nnkBlockExpr, nnkStmtListType, nnkBlockType, nnkWith, nnkWithout,
      nnkTypeOfExpr, nnkObjectTy, nnkTupleTy, nnkTupleClassTy, nnkTypeClassTy,
      nnkStaticTy, nnkRecList, nnkRecCase, nnkRecWhen, nnkRefTy, nnkPtrTy, nnkVarTy,
      nnkConstTy, nnkMutableTy, nnkDistinctTy, nnkProcTy, nnkIteratorTy, nnkSharedTy,
      nnkEnumTy, nnkEnumFieldDef, nnkArglist, nnkPattern, nnkHiddenTryStmt, nnkClosure,
      nnkGotoState, nnkState, nnkBreakState, nnkFuncDef, nnkTupleConstr

  Source Edit

    NimNodeKinds = set[NimNodeKind]

  Source Edit

    NimTypeKind = enum
      ntyNone, ntyBool, ntyChar, ntyEmpty, ntyAlias, ntyNil, ntyExpr, ntyStmt, ntyTypeDesc,
      ntyGenericInvocation, ntyGenericBody, ntyGenericInst, ntyGenericParam,
      ntyDistinct, ntyEnum, ntyOrdinal, ntyArray, ntyObject, ntyTuple, ntySet, ntyRange,
      ntyPtr, ntyRef, ntyVar, ntySequence, ntyProc, ntyPointer, ntyOpenArray, ntyString,
      ntyCString, ntyForward, ntyInt, ntyInt8, ntyInt16, ntyInt32, ntyInt64, ntyFloat,
      ntyFloat32, ntyFloat64, ntyFloat128, ntyUInt, ntyUInt8, ntyUInt16, ntyUInt32,
      ntyUInt64, ntyUnused0, ntyUnused1, ntyUnused2, ntyVarargs, ntyUncheckedArray,
      ntyError, ntyBuiltinTypeClass, ntyUserTypeClass, ntyUserTypeClassInst,
      ntyCompositeTypeClass, ntyInferred, ntyAnd, ntyOr, ntyNot, ntyAnything, ntyStatic,
      ntyFromExpr, ntyOpt, ntyVoid

  Source Edit

    TNimTypeKinds {...}{.deprecated.} = set[NimTypeKind]

  Source Edit

    NimSymKind = enum
      nskUnknown, nskConditional, nskDynLib, nskParam, nskGenericParam, nskTemp,
      nskModule, nskType, nskVar, nskLet, nskConst, nskResult, nskProc, nskFunc, nskMethod,
      nskIterator, nskConverter, nskMacro, nskTemplate, nskField, nskEnumField, nskForVar,
      nskLabel, nskStub

  Source Edit

    TNimSymKinds {...}{.deprecated.} = set[NimSymKind]

  Source Edit

    NimIdent {...}{.deprecated.} = object of RootObj

  Represents a Nim identifier in the AST. Note: This is only rarely useful, for identifier construction from a string use `ident"abc"`. Source Edit

    NimSym {...}{.deprecated.} = ref NimSymObj

  Represents a Nim symbol in the compiler; a symbol is a looked-up ident. Source Edit

    BindSymRule = enum
      brClosed,                   ## only the symbols in current scope are bound
      brOpen,                     ## open wrt overloaded symbols, but may be a single
             ## symbol if not ambiguous (the rules match that of
             ## binding in generics)
      brForceOpen                 ## same as brOpen, but it will always be open even
                 ## if not ambiguous (this cannot be achieved with
                 ## any other means in the language currently)

  specifies how `bindSym` behaves Source Edit

    LineInfo = object
      filename*: string
      line*, column*: int

  Source Edit

# Consts

    nnkLiterals = {nnkCharLit..nnkNilLit}

  Source Edit

    nnkCallKinds = {nnkCall, nnkInfix, nnkPrefix, nnkPostfix, nnkCommand, nnkCallStrLit}

  Source Edit

    RoutineNodes = {nnkProcDef, nnkFuncDef, nnkMethodDef, nnkDo, nnkLambda, nnkIteratorDef,
                  nnkTemplateDef, nnkConverterDef}

  Source Edit

    AtomicNodes = {nnkNone..nnkNilLit}

  Source Edit

    CallNodes = {nnkCall, nnkInfix, nnkPrefix, nnkPostfix, nnkCommand, nnkCallStrLit,
               nnkHiddenCallConv}

  Source Edit

# Procs

    proc `!`(s: string): NimIdent {...}{.magic: "StrToIdent", noSideEffect, deprecated: "Deprecated since version 0.18.0: Use \'ident\' or \'newIdentNode\' instead.".}

  Deprecated: Deprecated since version 0.18.0: Use 'ident' or 'newIdentNode' instead.
  Constructs an identifier from the string `s`. Source Edit

    proc toNimIdent(s: string): NimIdent {...}{.magic: "StrToIdent", noSideEffect, deprecated: "Deprecated since version 0.18.0: Use \'ident\' or \'newIdentNode\' instead.".}

  Deprecated: Deprecated since version 0.18.0: Use 'ident' or 'newIdentNode' instead.
  Constructs an identifier from the string `s`. Source Edit

    proc `==`(a, b: NimIdent): bool {...}{.magic: "EqIdent", noSideEffect, deprecated: "Deprecated since version 0.18.1; Use \'==\' on \'NimNode\' instead.".}

  Deprecated: Deprecated since version 0.18.1; Use '==' on 'NimNode' instead.
  Compares two Nim identifiers. Source Edit

    proc `==`(a, b: NimNode): bool {...}{.magic: "EqNimrodNode", noSideEffect.}

  Compare two Nim nodes. Return true if nodes are structurally equivalent. This means two independently created nodes can be equal. Source Edit

    proc `==`(a, b: NimSym): bool {...}{.magic: "EqNimrodNode", noSideEffect, deprecated: "Deprecated since version 0.18.1; Use \'==(NimNode, NimNode)\' instead.".}

  Deprecated: Deprecated since version 0.18.1; Use '==(NimNode, NimNode)' instead.
  Compares two Nim symbols. Source Edit

    proc sameType(a, b: NimNode): bool {...}{.magic: "SameNodeType", noSideEffect, raises: [],
                                    tags: [].}

  Compares two Nim nodes' types. Return true if the types are the same, eg. true when comparing alias with original type. Source Edit

    proc len(n: NimNode): int {...}{.magic: "NLen", noSideEffect.}

  Returns the number of children of `n`. Source Edit

    proc `[]`(n: NimNode; i: int): NimNode {...}{.magic: "NChild", noSideEffect.}

  Get `n`'s `i`'th child. Source Edit

    proc `[]`(n: NimNode; i: BackwardsIndex): NimNode {...}{.raises: [], tags: [].}

  Get `n`'s `i`'th child. Source Edit

    proc `[]`[T, U](n: NimNode; x: HSlice[T, U]): seq[NimNode]

  Slice operation for NimNode. Returns a seq of child of `n` who inclusive range [n[x.a], n[x.b]]. Source Edit

    proc `[]=`(n: NimNode; i: int; child: NimNode) {...}{.magic: "NSetChild", noSideEffect.}

  Set `n`'s `i`'th child to `child`. Source Edit

    proc `[]=`(n: NimNode; i: BackwardsIndex; child: NimNode) {...}{.raises: [], tags: [].}

  Set `n`'s `i`'th child to `child`. Source Edit

    proc add(father, child: NimNode): NimNode {...}{.magic: "NAdd", discardable, noSideEffect,
                                           locks: 0.}

  Adds the `child` to the `father` node. Returns the father node so that calls can be nested. Source Edit

    proc add(father: NimNode; children: varargs[NimNode]): NimNode {...}{.
        magic: "NAddMultiple", discardable, noSideEffect, locks: 0.}

  Adds each child of `children` to the `father` node. Returns the `father` node so that calls can be nested. Source Edit

    proc del(father: NimNode; idx = 0; n = 1) {...}{.magic: "NDel", noSideEffect.}

  Deletes `n` children of `father` starting at index `idx`. Source Edit

    proc kind(n: NimNode): NimNodeKind {...}{.magic: "NKind", noSideEffect.}

  Returns the `kind` of the node `n`. Source Edit

    proc intVal(n: NimNode): BiggestInt {...}{.magic: "NIntVal", noSideEffect.}

  Returns an integer value from any integer literal or enum field symbol. Source Edit

    proc floatVal(n: NimNode): BiggestFloat {...}{.magic: "NFloatVal", noSideEffect.}

  Returns a float from any floating point literal. Source Edit

    proc ident(n: NimNode): NimIdent {...}{.magic: "NIdent", noSideEffect, deprecated: "Deprecated since version 0.18.1; All functionality is defined on \'NimNode\'.".}

  Deprecated: Deprecated since version 0.18.1; All functionality is defined on 'NimNode'.
  Source Edit

    proc symbol(n: NimNode): NimSym {...}{.magic: "NSymbol", noSideEffect, deprecated: "Deprecated since version 0.18.1; All functionality is defined on \'NimNode\'.".}

  Deprecated: Deprecated since version 0.18.1; All functionality is defined on 'NimNode'.
  Source Edit

    proc getImpl(s: NimSym): NimNode {...}{.magic: "GetImpl", noSideEffect, deprecated: "use `getImpl: NimNode -> NimNode` instead".}

  Deprecated: use `getImpl: NimNode -> NimNode` instead
  Source Edit

    proc symKind(symbol: NimNode): NimSymKind {...}{.magic: "NSymKind", noSideEffect.}

  Source Edit

    proc getImpl(symbol: NimNode): NimNode {...}{.magic: "GetImpl", noSideEffect.}

  Returns a copy of the declaration of a symbol or `nil`. Source Edit

    proc strVal(n: NimNode): string {...}{.magic: "NStrVal", noSideEffect.}

  Returns the string value of an identifier, symbol, comment, or string literal.

  See also:

  - strVal= proc for setting the string value.
  Source Edit

    proc `$`(i: NimIdent): string {...}{.magic: "NStrVal", noSideEffect, deprecated: "Deprecated since version 0.18.1; Use \'strVal\' instead.".}

  Deprecated: Deprecated since version 0.18.1; Use 'strVal' instead.
  Converts a Nim identifier to a string. Source Edit

    proc `$`(s: NimSym): string {...}{.magic: "NStrVal", noSideEffect, deprecated: "Deprecated since version 0.18.1; Use \'strVal\' instead.".}

  Deprecated: Deprecated since version 0.18.1; Use 'strVal' instead.
  Converts a Nim symbol to a string. Source Edit

    proc owner(sym: NimNode): NimNode {...}{.magic: "SymOwner", noSideEffect.}

  Accepts a node of kind `nnkSym` and returns its owner's symbol. The meaning of 'owner' depends on `sym`'s `NimSymKind` and declaration context. For top level declarations this is an `nskModule` symbol, for proc local variables an `nskProc` symbol, for enum/object fields an `nskType` symbol, etc. For symbols without an owner, `nil` is returned.

  See also:

  - symKind proc to get the kind of a symbol
  - getImpl proc to get the declaration of a symbol
  Source Edit

    proc isInstantiationOf(instanceProcSym, genProcSym: NimNode): bool {...}{.
        magic: "SymIsInstantiationOf", noSideEffect.}

  Checks if a proc symbol is an instance of the generic proc symbol. Useful to check proc symbols against generic symbols returned by `bindSym`. Source Edit

    proc getType(n: NimNode): NimNode {...}{.magic: "NGetType", noSideEffect.}

  With 'getType' you can access the node's type. A Nim type is mapped to a Nim AST too, so it's slightly confusing but it means the same API can be used to traverse types. Recursive types are flattened for you so there is no danger of infinite recursions during traversal. To resolve recursive types, you have to call 'getType' again. To see what kind of type it is, call `typeKind` on getType's result. Source Edit

    proc getType(n: typedesc): NimNode {...}{.magic: "NGetType", noSideEffect.}

  Version of `getType` which takes a `typedesc`. Source Edit

    proc typeKind(n: NimNode): NimTypeKind {...}{.magic: "NGetType", noSideEffect.}

  Returns the type kind of the node 'n' that should represent a type, that means the node should have been obtained via `getType`. Source Edit

    proc getTypeInst(n: NimNode): NimNode {...}{.magic: "NGetType", noSideEffect, raises: [],
                                        tags: [].}

  Returns the type of a node in a form matching the way the type instance was declared in the code.

  Examples:

      type
        Vec[N: static[int]; T] = object
          arr: array[N, T]

        Vec4[T] = Vec[4, T]
        Vec4f = Vec4[float32]
      var a: Vec4f
      var b: Vec4[float32]
      var c: Vec[4, float32]
      macro dumpTypeInst(x: typed): untyped =
        newLit(x.getTypeInst.repr)

      doAssert(dumpTypeInst(a) == "Vec4f")
      doAssert(dumpTypeInst(b) == "Vec4[float32]")
      doAssert(dumpTypeInst(c) == "Vec[4, float32]")

  Source Edit

    proc getTypeInst(n: typedesc): NimNode {...}{.magic: "NGetType", noSideEffect.}

  Version of `getTypeInst` which takes a `typedesc`. Source Edit

    proc getTypeImpl(n: NimNode): NimNode {...}{.magic: "NGetType", noSideEffect, raises: [],
                                        tags: [].}

  Returns the type of a node in a form matching the implementation of the type. Any intermediate aliases are expanded to arrive at the final type implementation. You can instead use `getImpl` on a symbol if you want to find the intermediate aliases.

  Examples:

      type
        Vec[N: static[int]; T] = object
          arr: array[N, T]

        Vec4[T] = Vec[4, T]
        Vec4f = Vec4[float32]
      var a: Vec4f
      var b: Vec4[float32]
      var c: Vec[4, float32]
      macro dumpTypeImpl(x: typed): untyped =
        newLit(x.getTypeImpl.repr)

      let t = """object
        arr: array[0 .. 3, float32]
      """
      doAssert(dumpTypeImpl(a) == t)
      doAssert(dumpTypeImpl(b) == t)
      doAssert(dumpTypeImpl(c) == t)

  Source Edit

    proc signatureHash(n: NimNode): string {...}{.magic: "NSigHash", noSideEffect.}

  Returns a stable identifier derived from the signature of a symbol. The signature combines many factors such as the type of the symbol, the owning module of the symbol and others. The same identifier is used in the back-end to produce the mangled symbol name. Source Edit

    proc symBodyHash(s: NimNode): string {...}{.noSideEffect, raises: [], tags: [].}

  Returns a stable digest for symbols derived not only from type signature and owning module, but also implementation body. All procs/variables used in the implementation of this symbol are hashed recursively as well, including magics from system module. Source Edit

    proc getTypeImpl(n: typedesc): NimNode {...}{.magic: "NGetType", noSideEffect.}

  Version of `getTypeImpl` which takes a `typedesc`. Source Edit

    proc intVal=(n: NimNode; val: BiggestInt) {...}{.magic: "NSetIntVal", noSideEffect.}

  Source Edit

    proc floatVal=(n: NimNode; val: BiggestFloat) {...}{.magic: "NSetFloatVal", noSideEffect.}

  Source Edit

    proc symbol=(n: NimNode; val: NimSym) {...}{.magic: "NSetSymbol", noSideEffect, deprecated: "Deprecated since version 0.18.1; Generate a new \'NimNode\' with \'genSym\' instead.".}

  Deprecated: Deprecated since version 0.18.1; Generate a new 'NimNode' with 'genSym' instead.
  Source Edit

    proc ident=(n: NimNode; val: NimIdent) {...}{.magic: "NSetIdent", noSideEffect, deprecated: "Deprecated since version 0.18.1; Generate a new \'NimNode\' with \'ident(string)\' instead.".}

  Deprecated: Deprecated since version 0.18.1; Generate a new 'NimNode' with 'ident(string)' instead.
  Source Edit

    proc strVal=(n: NimNode; val: string) {...}{.magic: "NSetStrVal", noSideEffect.}

  Sets the string value of a string literal or comment. Setting `strVal` is disallowed for `nnkIdent` and `nnkSym` nodes; a new node must be created using `ident` or `bindSym` instead.

  See also:

  - strVal proc for getting the string value.
  - ident proc for creating an identifier.
  - bindSym proc for binding a symbol.
  Source Edit

    proc newNimNode(kind: NimNodeKind; lineInfoFrom: NimNode = nil): NimNode {...}{.
        magic: "NNewNimNode", noSideEffect.}

  Creates a new AST node of the specified kind.

  The `lineInfoFrom` parameter is used for line information when the produced code crashes. You should ensure that it is set to a node that you are transforming.

  Source Edit

    proc copyNimNode(n: NimNode): NimNode {...}{.magic: "NCopyNimNode", noSideEffect.}

  Source Edit

    proc copyNimTree(n: NimNode): NimNode {...}{.magic: "NCopyNimTree", noSideEffect.}

  Source Edit

    proc error(msg: string; n: NimNode = nil) {...}{.magic: "NError", gcsafe, locks: 0.}

  Writes an error message at compile time. The optional `n: NimNode` parameter is used as the source for file and line number information in the compilation error message. Source Edit

    proc warning(msg: string; n: NimNode = nil) {...}{.magic: "NWarning", gcsafe, locks: 0.}

  Writes a warning message at compile time. Source Edit

    proc hint(msg: string; n: NimNode = nil) {...}{.magic: "NHint", gcsafe, locks: 0.}

  Writes a hint message at compile time. Source Edit

    proc newStrLitNode(s: string): NimNode {...}{.compileTime, noSideEffect, raises: [], tags: [].}

  Creates a string literal node from `s`. Source Edit

    proc newCommentStmtNode(s: string): NimNode {...}{.compileTime, noSideEffect, raises: [],
        tags: [].}

  Creates a comment statement node. Source Edit

    proc newIntLitNode(i: BiggestInt): NimNode {...}{.compileTime, raises: [], tags: [].}

  Creates an int literal node from `i`. Source Edit

    proc newFloatLitNode(f: BiggestFloat): NimNode {...}{.compileTime, raises: [], tags: [].}

  Creates a float literal node from `f`. Source Edit

    proc newIdentNode(i: NimIdent): NimNode {...}{.compileTime, deprecated, raises: [], tags: [].}

  Deprecated
  Creates an identifier node from `i`. Source Edit

    proc newIdentNode(i: string): NimNode {...}{.magic: "StrToIdent", noSideEffect, compilerproc.}

  Creates an identifier node from `i`. It is simply an alias for `ident(string)`. Use that, it's shorter. Source Edit

    proc bindSym(ident: string | NimNode; rule: BindSymRule = brClosed): NimNode {...}{.
        magic: "NBindSym", noSideEffect.}

  Ceates a node that binds `ident` to a symbol node. The bound symbol may be an overloaded symbol. if `ident` is a NimNode, it must have `nnkIdent` kind. If `rule == brClosed` either an `nnkClosedSymChoice` tree is returned or `nnkSym` if the symbol is not ambiguous. If `rule == brOpen` either an `nnkOpenSymChoice` tree is returned or `nnkSym` if the symbol is not ambiguous. If `rule == brForceOpen` always an `nnkOpenSymChoice` tree is returned even if the symbol is not ambiguous.

  Experimental feature: use {.experimental: "dynamicBindSym".} to activate it. If called from template / regular code, `ident` and `rule` must be constant expression / literal value. If called from macros / compile time procs / static blocks, `ident` and `rule` can be VM computed value.

  Source Edit

    proc genSym(kind: NimSymKind = nskLet; ident = ""): NimNode {...}{.magic: "NGenSym",
        noSideEffect.}

  Generates a fresh symbol that is guaranteed to be unique. The symbol needs to occur in a declaration context. Source Edit

    proc callsite(): NimNode {...}{.magic: "NCallSite", gcsafe, locks: 0, deprecated: "Deprecated since v0.18.1; use varargs[untyped] in the macro prototype instead".}

  Deprecated: Deprecated since v0.18.1; use varargs[untyped] in the macro prototype instead
  Returns the AST of the invocation expression that invoked this macro. Source Edit

    proc toStrLit(n: NimNode): NimNode {...}{.compileTime, raises: [], tags: [].}

  Converts the AST `n` to the concrete Nim code and wraps that in a string literal node. Source Edit

    proc `$`(arg: LineInfo): string {...}{.raises: [], tags: [].}

  Return a string representation in the form `filepath(line, column)`. Source Edit

    proc copyLineInfo(arg: NimNode; info: NimNode) {...}{.magic: "NLineInfo", noSideEffect.}

  Copy lineinfo from `info`. Source Edit

    proc lineInfoObj(n: NimNode): LineInfo {...}{.compileTime, raises: [], tags: [].}

  Returns `LineInfo` of `n`, using absolute path for `filename`. Source Edit

    proc lineInfo(arg: NimNode): string {...}{.compileTime, raises: [], tags: [].}

  Return line info in the form `filepath(line, column)`. Source Edit

    proc internalErrorFlag(): string {...}{.magic: "NError", noSideEffect.}

  Some builtins set an error flag. This is then turned into a proper exception. Note: Ordinary application code should not call this. Source Edit

    proc parseExpr(s: string): NimNode {...}{.noSideEffect, compileTime, raises: [ValueError],
                                     tags: [].}

  Compiles the passed string to its AST representation. Expects a single expression. Raises `ValueError` for parsing errors. Source Edit

    proc parseStmt(s: string): NimNode {...}{.noSideEffect, compileTime, raises: [ValueError],
                                     tags: [].}

  Compiles the passed string to its AST representation. Expects one or more statements. Raises `ValueError` for parsing errors. Source Edit

    proc getAst(macroOrTemplate: untyped): NimNode {...}{.magic: "ExpandToAst", noSideEffect.}

  Obtains the AST nodes returned from a macro or template invocation. Example:

      macro FooMacro() =
        var ast = getAst(BarTemplate())

  Source Edit

    proc quote(bl: typed; op = "``"): NimNode {...}{.magic: "QuoteAst", noSideEffect.}

  Quasi-quoting operator. Accepts an expression or a block and returns the AST that represents it. Within the quoted AST, you are able to interpolate NimNode expressions from the surrounding scope. If no operator is given, quoting is done using backticks. Otherwise, the given operator must be used as a prefix operator for any interpolated expression.

  Example:

      macro check(ex: untyped) =
        # this is a simplified version of the check macro from the
        # unittest module.

        # If there is a failed check, we want to make it easy for
        # the user to jump to the faulty line in the code, so we
        # get the line info here:
        var info = ex.lineinfo

        # We will also display the code string of the failed check:
        var expString = ex.toStrLit

        # Finally we compose the code to implement the check:
        result = quote do:
          if not `ex`:
            echo `info` & ": Check failed: " & `expString`

  Source Edit

    proc expectKind(n: NimNode; k: NimNodeKind) {...}{.compileTime, raises: [], tags: [].}

  Checks that `n` is of kind `k`. If this is not the case, compilation aborts with an error message. This is useful for writing macros that check the AST that is passed to them. Source Edit

    proc expectMinLen(n: NimNode; min: int) {...}{.compileTime, raises: [], tags: [].}

  Checks that `n` has at least `min` children. If this is not the case, compilation aborts with an error message. This is useful for writing macros that check its number of arguments. Source Edit

    proc expectLen(n: NimNode; len: int) {...}{.compileTime, raises: [], tags: [].}

  Checks that `n` has exactly `len` children. If this is not the case, compilation aborts with an error message. This is useful for writing macros that check its number of arguments. Source Edit

    proc expectLen(n: NimNode; min, max: int) {...}{.compileTime, raises: [], tags: [].}

  Checks that `n` has a number of children in the range `min..max`. If this is not the case, compilation aborts with an error message. This is useful for writing macros that check its number of arguments. Source Edit

    proc newTree(kind: NimNodeKind; children: varargs[NimNode]): NimNode {...}{.compileTime,
        raises: [], tags: [].}

  Produces a new node with children. Source Edit

    proc newCall(theProc: NimNode; args: varargs[NimNode]): NimNode {...}{.compileTime,
        raises: [], tags: [].}

  Produces a new call node. `theProc` is the proc that is called with the arguments `args[0..]`. Source Edit

    proc newCall(theProc: NimIdent; args: varargs[NimNode]): NimNode {...}{.compileTime, deprecated: "Deprecated since v0.18.1; use \'newCall(string, ...)\' or \'newCall(NimNode, ...)\' instead",
        raises: [], tags: [].}

  Deprecated: Deprecated since v0.18.1; use 'newCall(string, ...)' or 'newCall(NimNode, ...)' instead
  Produces a new call node. `theProc` is the proc that is called with the arguments `args[0..]`. Source Edit

    proc newCall(theProc: string; args: varargs[NimNode]): NimNode {...}{.compileTime,
        raises: [], tags: [].}

  Produces a new call node. `theProc` is the proc that is called with the arguments `args[0..]`. Source Edit

    proc newLit(c: char): NimNode {...}{.compileTime, raises: [], tags: [].}

  Produces a new character literal node. Source Edit

    proc newLit(i: int): NimNode {...}{.compileTime, raises: [], tags: [].}

  Produces a new integer literal node. Source Edit

    proc newLit(i: int8): NimNode {...}{.compileTime, raises: [], tags: [].}

  Produces a new integer literal node. Source Edit

    proc newLit(i: int16): NimNode {...}{.compileTime, raises: [], tags: [].}

  Produces a new integer literal node. Source Edit

    proc newLit(i: int32): NimNode {...}{.compileTime, raises: [], tags: [].}

  Produces a new integer literal node. Source Edit

    proc newLit(i: int64): NimNode {...}{.compileTime, raises: [], tags: [].}

  Produces a new integer literal node. Source Edit

    proc newLit(i: uint): NimNode {...}{.compileTime, raises: [], tags: [].}

  Produces a new unsigned integer literal node. Source Edit

    proc newLit(i: uint8): NimNode {...}{.compileTime, raises: [], tags: [].}

  Produces a new unsigned integer literal node. Source Edit

    proc newLit(i: uint16): NimNode {...}{.compileTime, raises: [], tags: [].}

  Produces a new unsigned integer literal node. Source Edit

    proc newLit(i: uint32): NimNode {...}{.compileTime, raises: [], tags: [].}

  Produces a new unsigned integer literal node. Source Edit

    proc newLit(i: uint64): NimNode {...}{.compileTime, raises: [], tags: [].}

  Produces a new unsigned integer literal node. Source Edit

    proc newLit(b: bool): NimNode {...}{.compileTime, raises: [], tags: [].}

  Produces a new boolean literal node. Source Edit

    proc newLit(f: float32): NimNode {...}{.compileTime, raises: [], tags: [].}

  Produces a new float literal node. Source Edit

    proc newLit(f: float64): NimNode {...}{.compileTime, raises: [], tags: [].}

  Produces a new float literal node. Source Edit

    proc newLit(arg: enum): NimNode {...}{.compileTime.}

  Source Edit

    proc newLit(arg: object): NimNode {...}{.compileTime.}

  Source Edit

    proc newLit[N, T](arg: array[N, T]): NimNode {...}{.compileTime.}

  Source Edit

    proc newLit[T](arg: seq[T]): NimNode {...}{.compileTime.}

  Source Edit

    proc newLit[T](s: set[T]): NimNode {...}{.compileTime.}

  Source Edit

    proc newLit(arg: tuple): NimNode {...}{.compileTime.}

  Source Edit

    proc newLit(s: string): NimNode {...}{.compileTime, raises: [], tags: [].}

  Produces a new string literal node. Source Edit

    proc nestList(op: NimNode; pack: NimNode): NimNode {...}{.compileTime, raises: [], tags: [].}

  Nests the list `pack` into a tree of call expressions: `[a, b, c]` is transformed into `op(a, op(c, d))`. This is also known as fold expression. Source Edit

    proc nestList(op: NimNode; pack: NimNode; init: NimNode): NimNode {...}{.compileTime,
        raises: [], tags: [].}

  Nests the list `pack` into a tree of call expressions: `[a, b, c]` is transformed into `op(a, op(c, d))`. This is also known as fold expression. Source Edit

    proc nestList(theProc: NimIdent; x: NimNode): NimNode {...}{.compileTime, deprecated: "Deprecated since v0.18.1; use one of \'nestList(NimNode, ...)\' instead.",
        raises: [], tags: [].}

  Deprecated: Deprecated since v0.18.1; use one of 'nestList(NimNode, ...)' instead.
  Source Edit

    proc treeRepr(n: NimNode): string {...}{.compileTime, gcsafe, locks: 0, raises: [], tags: [].}

  Convert the AST `n` to a human-readable tree-like string.

  See also `repr`, `lispRepr`, and `astGenRepr`.

  Source Edit

    proc lispRepr(n: NimNode; indented = false): string {...}{.compileTime, gcsafe, locks: 0,
        raises: [], tags: [].}

  Convert the AST `n` to a human-readable lisp-like string.

  See also `repr`, `treeRepr`, and `astGenRepr`.

  Source Edit

    proc astGenRepr(n: NimNode): string {...}{.compileTime, gcsafe, locks: 0, raises: [], tags: [].}

  Convert the AST `n` to the code required to generate that AST.

  See also `repr`, `treeRepr`, and `lispRepr`.

  Source Edit

    proc newEmptyNode(): NimNode {...}{.compileTime, noSideEffect, raises: [], tags: [].}

  Create a new empty node. Source Edit

    proc newStmtList(stmts: varargs[NimNode]): NimNode {...}{.compileTime, raises: [], tags: [].}

  Create a new statement list. Source Edit

    proc newPar(exprs: varargs[NimNode]): NimNode {...}{.compileTime, raises: [], tags: [].}

  Create a new parentheses-enclosed expression. Source Edit

    proc newBlockStmt(label, body: NimNode): NimNode {...}{.compileTime, raises: [], tags: [].}

  Create a new block statement with label. Source Edit

    proc newBlockStmt(body: NimNode): NimNode {...}{.compileTime, raises: [], tags: [].}

  Create a new block: stmt. Source Edit

    proc newVarStmt(name, value: NimNode): NimNode {...}{.compileTime, raises: [], tags: [].}

  Create a new var stmt. Source Edit

    proc newLetStmt(name, value: NimNode): NimNode {...}{.compileTime, raises: [], tags: [].}

  Create a new let stmt. Source Edit

    proc newConstStmt(name, value: NimNode): NimNode {...}{.compileTime, raises: [], tags: [].}

  Create a new const stmt. Source Edit

    proc newAssignment(lhs, rhs: NimNode): NimNode {...}{.compileTime, raises: [], tags: [].}

  Source Edit

    proc newDotExpr(a, b: NimNode): NimNode {...}{.compileTime, raises: [], tags: [].}

  Create new dot expression. a.dot(b) -> `a.b` Source Edit

    proc newColonExpr(a, b: NimNode): NimNode {...}{.compileTime, raises: [], tags: [].}

  Create new colon expression. newColonExpr(a, b) -> `a: b` Source Edit

    proc newIdentDefs(name, kind: NimNode; default = newEmptyNode()): NimNode {...}{.compileTime,
        raises: [], tags: [].}

  Creates a new `nnkIdentDefs` node of a specific kind and value.

  `nnkIdentDefs` need to have at least three children, but they can have more: first comes a list of identifiers followed by a type and value nodes. This helper proc creates a three node subtree, the first subnode being a single identifier name. Both the `kind` node and `default` (value) nodes may be empty depending on where the `nnkIdentDefs` appears: tuple or object definitions will have an empty `default` node, `let` or `var` blocks may have an empty `kind` node if the identifier is being assigned a value. Example:

      var varSection = newNimNode(nnkVarSection).add(
        newIdentDefs(ident("a"), ident("string")),
        newIdentDefs(ident("b"), newEmptyNode(), newLit(3)))
      # --> var
      #       a: string
      #       b = 3

  If you need to create multiple identifiers you need to use the lower level `newNimNode`:

      result = newNimNode(nnkIdentDefs).add(
        ident("a"), ident("b"), ident("c"), ident("string"),
          newStrLitNode("Hello"))

  Source Edit

    proc newNilLit(): NimNode {...}{.compileTime, raises: [], tags: [].}

  New nil literal shortcut. Source Edit

    proc last(node: NimNode): NimNode {...}{.compileTime, raises: [], tags: [].}

  Return the last item in nodes children. Same as `node[^1]`. Source Edit

    proc expectKind(n: NimNode; k: set[NimNodeKind]) {...}{.compileTime, raises: [], tags: [].}

  Checks that `n` is of kind `k`. If this is not the case, compilation aborts with an error message. This is useful for writing macros that check the AST that is passed to them. Source Edit

    proc newProc(name = newEmptyNode(); params: openArray[NimNode] = [newEmptyNode()];
                body: NimNode = newStmtList(); procType = nnkProcDef;
                pragmas: NimNode = newEmptyNode()): NimNode {...}{.compileTime, raises: [],
        tags: [].}

  Shortcut for creating a new proc.

  The `params` array must start with the return type of the proc, followed by a list of IdentDefs which specify the params.

  Source Edit

    proc newIfStmt(branches: varargs[tuple[cond, body: NimNode]]): NimNode {...}{.compileTime,
        raises: [], tags: [].}

  Constructor for `if` statements.

      newIfStmt(
        (Ident, StmtList),
        ...
      )

  Source Edit

    proc newEnum(name: NimNode; fields: openArray[NimNode]; public, pure: bool): NimNode {...}{.
        compileTime, raises: [], tags: [].}

  Creates a new enum. `name` must be an ident. Fields are allowed to be either idents or EnumFieldDef

      newEnum(
        name    = ident("Colors"),
        fields  = [ident("Blue"), ident("Red")],
        public  = true, pure = false)

      # type Colors* = Blue Red

  Source Edit

    proc copyChildrenTo(src, dest: NimNode) {...}{.compileTime, raises: [], tags: [].}

  Copy all children from `src` to `dest`. Source Edit

    proc name(someProc: NimNode): NimNode {...}{.compileTime, raises: [], tags: [].}

  Source Edit

    proc name=(someProc: NimNode; val: NimNode) {...}{.compileTime, raises: [], tags: [].}

  Source Edit

    proc params(someProc: NimNode): NimNode {...}{.compileTime, raises: [], tags: [].}

  Source Edit

    proc params=(someProc: NimNode; params: NimNode) {...}{.compileTime, raises: [], tags: [].}

  Source Edit

    proc pragma(someProc: NimNode): NimNode {...}{.compileTime, raises: [], tags: [].}

  Get the pragma of a proc type. These will be expanded. Source Edit

    proc pragma=(someProc: NimNode; val: NimNode) {...}{.compileTime, raises: [], tags: [].}

  Set the pragma of a proc type. Source Edit

    proc addPragma(someProc, pragma: NimNode) {...}{.compileTime, raises: [], tags: [].}

  Adds pragma to routine definition. Source Edit

    proc body(someProc: NimNode): NimNode {...}{.compileTime, raises: [], tags: [].}

  Source Edit

    proc body=(someProc: NimNode; val: NimNode) {...}{.compileTime, raises: [], tags: [].}

  Source Edit

    proc `$`(node: NimNode): string {...}{.compileTime, raises: [Exception], tags: [RootEffect].}

  Get the string of an identifier node. Source Edit

    proc ident(name: string): NimNode {...}{.magic: "StrToIdent", noSideEffect.}

  Create a new ident node from a string. Source Edit

    proc insert(a: NimNode; pos: int; b: NimNode) {...}{.compileTime, raises: [], tags: [].}

  Insert node `b` into node `a` at `pos`. Source Edit

    proc basename(a: NimNode): NimNode {...}{.compileTime, gcsafe, locks: 0, raises: [], tags: [].}

  Pull an identifier from prefix/postfix expressions. Source Edit

    proc basename=(a: NimNode; val: string) {...}{.compileTime, raises: [], tags: [].}

  Source Edit

    proc postfix(node: NimNode; op: string): NimNode {...}{.compileTime, raises: [], tags: [].}

  Source Edit

    proc prefix(node: NimNode; op: string): NimNode {...}{.compileTime, raises: [], tags: [].}

  Source Edit

    proc infix(a: NimNode; op: string; b: NimNode): NimNode {...}{.compileTime, raises: [], tags: [].}

  Source Edit

    proc unpackPostfix(node: NimNode): tuple[node: NimNode, op: string] {...}{.compileTime,
        raises: [Exception], tags: [RootEffect].}

  Source Edit

    proc unpackPrefix(node: NimNode): tuple[node: NimNode, op: string] {...}{.compileTime,
        raises: [Exception], tags: [RootEffect].}

  Source Edit

    proc unpackInfix(node: NimNode): tuple[left: NimNode, op: string, right: NimNode] {...}{.
        compileTime, raises: [Exception], tags: [RootEffect].}

  Source Edit

    proc copy(node: NimNode): NimNode {...}{.compileTime, raises: [], tags: [].}

  An alias for copyNimTree. Source Edit

    proc eqIdent(a: string; b: string): bool {...}{.magic: "EqIdent", noSideEffect.}

  Style insensitive comparison. Source Edit

    proc eqIdent(a: NimNode; b: string): bool {...}{.magic: "EqIdent", noSideEffect.}

  Style insensitive comparison. `a` can be an identifier or a symbol. Source Edit

    proc eqIdent(a: string; b: NimNode): bool {...}{.magic: "EqIdent", noSideEffect.}

  Style insensitive comparison. `b` can be an identifier or a symbol. Source Edit

    proc eqIdent(a: NimNode; b: NimNode): bool {...}{.magic: "EqIdent", noSideEffect.}

  Style insensitive comparison. `a` and `b` can be an identifier or a symbol. Source Edit

    proc hasArgOfName(params: NimNode; name: string): bool {...}{.compileTime,
        raises: [Exception], tags: [RootEffect].}

  Search `nnkFormalParams` for an argument. Source Edit

    proc addIdentIfAbsent(dest: NimNode; ident: string) {...}{.compileTime,
        raises: [Exception], tags: [RootEffect].}

  Add `ident` to `dest` if it is not present. This is intended for use with pragmas. Source Edit

    proc boolVal(n: NimNode): bool {...}{.compileTime, noSideEffect, raises: [], tags: [].}

  Source Edit

    proc nodeID(n: NimNode): int {...}{.magic: NodeId.}

  Returns the id of `n`, when the compiler has been compiled with the flag `-d:useNodeids`, otherwise returns `-1`. This proc is for the purpose to debug the compiler only. Source Edit

    proc getProjectPath(): string {...}{.raises: [], tags: [].}

  Returns the path to the currently compiling project, not to be confused with `system.currentSourcePath` which returns the path of the current module. Source Edit

    proc getSize(arg: NimNode): int {...}{.magic: "NSizeOf", noSideEffect, raises: [], tags: [].}

  Returns the same result as `system.sizeof` if the size is known by the Nim compiler. Returns a negative value if the Nim compiler does not know the size. Source Edit

    proc getAlign(arg: NimNode): int {...}{.magic: "NSizeOf", noSideEffect, raises: [], tags: [].}

  Returns the same result as `system.alignof` if the alignment is known by the Nim compiler. It works on `NimNode` for use in macro context. Returns a negative value if the Nim compiler does not know the alignment. Source Edit

    proc getOffset(arg: NimNode): int {...}{.magic: "NSizeOf", noSideEffect, raises: [], tags: [].}

  Returns the same result as `system.offsetof` if the offset is known by the Nim compiler. It expects a resolved symbol node from a field of a type. Therefore it only requires one argument instead of two. Returns a negative value if the Nim compiler does not know the offset. Source Edit

    proc isExported(n: NimNode): bool {...}{.noSideEffect, raises: [], tags: [].}

  Returns whether the symbol is exported or not. Source Edit

# Iterators

    iterator items(n: NimNode): NimNode {...}{.inline, raises: [], tags: [].}

  Iterates over the children of the NimNode `n`. Source Edit

    iterator pairs(n: NimNode): (int, NimNode) {...}{.inline, raises: [], tags: [].}

  Iterates over the children of the NimNode `n` and its indices. Source Edit

    iterator children(n: NimNode): NimNode {...}{.inline, raises: [], tags: [].}

  Iterates over the children of the NimNode `n`. Source Edit

# Macros

    macro dumpTree(s: untyped): untyped

  Accepts a block of nim code and prints the parsed abstract syntax tree using the `treeRepr` proc. Printing is done at compile time.

  You can use this as a tool to explore the Nim's abstract syntax tree and to discover what kind of nodes must be created to represent a certain expression/statement.

  For example:

      dumpTree:
        echo "Hello, World!"

  Outputs:

      StmtList
        Command
          Ident "echo"
          StrLit "Hello, World!"

  Also see `dumpAstGen` and `dumpLisp`.

  Source Edit

    macro dumpLisp(s: untyped): untyped

  Accepts a block of nim code and prints the parsed abstract syntax tree using the `lispRepr` proc. Printing is done at compile time.

  You can use this as a tool to explore the Nim's abstract syntax tree and to discover what kind of nodes must be created to represent a certain expression/statement.

  For example:

      dumpLisp:
        echo "Hello, World!"

  Outputs:

      (StmtList
       (Command
        (Ident "echo")
        (StrLit "Hello, World!")))

  Also see `dumpAstGen` and `dumpTree`.

  Source Edit

    macro dumpAstGen(s: untyped): untyped

  Accepts a block of nim code and prints the parsed abstract syntax tree using the `astGenRepr` proc. Printing is done at compile time.

  You can use this as a tool to write macros quicker by writing example outputs and then copying the snippets into the macro for modification.

  For example:

      dumpAstGen:
        echo "Hello, World!"

  Outputs:

      nnkStmtList.newTree(
        nnkCommand.newTree(
          newIdentNode("echo"),
          newLit("Hello, World!")
        )
      )

  Also see `dumpTree` and `dumpLisp`.

  Source Edit

    macro dumpTreeImm(s: untyped): untyped {...}{.deprecated.}

  Deprecated
  Deprecated. Use `dumpTree` instead. Source Edit

    macro dumpLispImm(s: untyped): untyped {...}{.deprecated.}

  Deprecated
  Deprecated. Use `dumpLisp` instead. Source Edit

    macro expandMacros(body: typed): untyped

  Expands one level of macro - useful for debugging. Can be used to inspect what happens when a macro call is expanded, without altering its result.

  For instance,

      import future, macros

      let
        x = 10
        y = 20
      expandMacros:
        dump(x + y)

  will actually dump `x + y`, but at the same time will print at compile time the expansion of the `dump` macro, which in this case is `debugEcho ["x + y", " = ", x + y]`.

  Source Edit

    macro hasCustomPragma(n: typed; cp: typed{nkSym}): untyped

  Expands to `true` if expression `n` which is expected to be `nnkDotExpr` (if checking a field), a proc or a type has custom pragma `cp`.

  See also `getCustomPragmaVal`.

      template myAttr() {.pragma.}
      type
        MyObj = object
          myField {.myAttr.}: int

      proc myProc() {.myAttr.} = discard

      var o: MyObj
      assert(o.myField.hasCustomPragma(myAttr))
      assert(myProc.hasCustomPragma(myAttr))

  Source Edit

    macro getCustomPragmaVal(n: typed; cp: typed{nkSym}): untyped

  Expands to value of custom pragma `cp` of expression `n` which is expected to be `nnkDotExpr`, a proc or a type.

  See also `hasCustomPragma`

      template serializationKey(key: string) {.pragma.}
      type
        MyObj {.serializationKey: "mo".} = object
          myField {.serializationKey: "mf".}: int
      var o: MyObj
      assert(o.myField.getCustomPragmaVal(serializationKey) == "mf")
      assert(o.getCustomPragmaVal(serializationKey) == "mo")
      assert(MyObj.getCustomPragmaVal(serializationKey) == "mo")

  Source Edit

    macro unpackVarargs(callee: untyped; args: varargs[untyped]): untyped

  Source Edit

# Templates

    template `or`(x, y: NimNode): NimNode

  Evaluate `x` and when it is not an empty node, return it. Otherwise evaluate to `y`. Can be used to chain several expressions to get the first expression that is not empty.

      let node = mightBeEmpty() or mightAlsoBeEmpty() or fallbackNode

  Source Edit

    template findChild(n: NimNode; cond: untyped): NimNode {...}{.dirty.}

  Find the first child node matching condition (or nil).

      var res = findChild(n, it.kind == nnkPostfix and
                             it.basename.ident == toNimIdent"foo")

  Source Edit

    template emit(e: static[string]): untyped {...}{.deprecated.}

  Deprecated
  Accepts a single string argument and treats it as nim code that should be inserted verbatim in the program Example:

      emit("echo " & '"' & "hello world".toUpper & '"')

  Deprecated since version 0.15 since it's so rarely useful.

  Source Edit