[#58149] [ruby-trunk - Feature #9076][Open] New one-argument block syntax: &. — "asterite (Ary Borenszweig)" <ary@...>
23 messages
2013/11/04
[#58259] [ruby-trunk - Feature #9099][Open] Train emoji lambda operator — "charliesome (Charlie Somerville)" <charliesome@...>
9 messages
2013/11/10
[#58312] [ruby-trunk - Feature #9107][Open] Introduce YES and NO as aliases of true and false — "gsamokovarov (Genadi Samokovarov)" <gsamokovarov@...>
5 messages
2013/11/13
[#58350] [ruby-trunk - Feature #9113][Open] Ship Ruby for Linux with jemalloc out-of-the-box — "sam.saffron (Sam Saffron)" <sam.saffron@...>
59 messages
2013/11/15
[#60851] Re: [ruby-trunk - Feature #9113][Open] Ship Ruby for Linux with jemalloc out-of-the-box
— Eric Wong <normalperson@...>
2014/02/19
Btw, I also hope to experiment with a slab allocator since many internal
[#62721] [ruby-trunk - Feature #9113] Ship Ruby for Linux with jemalloc out-of-the-box
— nobu@...
2014/05/24
Issue #9113 has been updated by Nobuyoshi Nakada.
[#62735] [ruby-trunk - Feature #9113] Ship Ruby for Linux with jemalloc out-of-the-box
— normalperson@...
2014/05/25
Issue #9113 has been updated by Eric Wong.
[#58391] [ruby-trunk - Bug #9119][Assigned] TestTime#test_marshal_broken_offset broken under MinGW — "luislavena (Luis Lavena)" <luislavena@...>
10 messages
2013/11/17
[#58396] [ruby-trunk - Bug #9121][Open] [PATCH] Remove rbtree implementation of SortedSet due to performance regression — "xshay (Xavier Shay)" <contact@...>
15 messages
2013/11/18
[#58404] [ruby-trunk - Feature #9123][Open] Make Numeric#nonzero? behavior consistent with Numeric#zero? — "sferik (Erik Michaels-Ober)" <sferik@...>
40 messages
2013/11/18
[#58411] [ruby-trunk - Bug #9124][Open] TestSocket errors in test-all on Arch 64-bit — "jonforums (Jon Forums)" <redmine@...>
14 messages
2013/11/18
[#58515] [ruby-trunk - Bug #9124] TestSocket errors in test-all on Arch 64-bit
— "jonforums (Jon Forums)" <redmine@...>
2013/11/23
[#58841] [ruby-trunk - Bug #9124] TestSocket errors in test-all on Arch 64-bit
— "jonforums (Jon Forums)" <redmine@...>
2013/12/04
[#58842] Re: [ruby-trunk - Bug #9124] TestSocket errors in test-all on Arch 64-bit
— Eric Wong <normalperson@...>
2013/12/04
"jonforums (Jon Forums)" <[email protected]> wrote:
[#58452] [ruby-trunk - Bug #9133][Open] logger rotates log files more than expected — "no6v (Nobuhiro IMAI)" <nov@...>
8 messages
2013/11/21
[#58473] Object identity for string hash keys — Andrew Vit <andrew@...>
I'm not sure if this is a bug. I'm creating a hash like this:
5 messages
2013/11/21
[#58490] Re: [ruby-cvs:50910] drbrain:r43767 (trunk): * lib/rubygems: Update to RubyGems master 50a8210. Important changes — Tanaka Akira <akr@...>
2013/11/22 <[email protected]>:
4 messages
2013/11/22
[#58492] Re: [ruby-cvs:50910] drbrain:r43767 (trunk): * lib/rubygems: Update to RubyGems master 50a8210. Important changes
— Eric Wong <normalperson@...>
2013/11/22
Tanaka Akira <[email protected]> wrote:
[#58496] [ruby-trunk - Feature #9140][Open] Allow each_with_index to get start index — "rosenfeld (Rodrigo Rosenfeld Rosas)" <rr.rosas@...>
8 messages
2013/11/22
[#58545] [ruby-trunk - Feature #9145][Open] Queue#pop(true) return nil if empty instead of raising ThreadError — "jsc (Justin Collins)" <redmine@...>
9 messages
2013/11/24
[#58599] [ruby-trunk - Bug #9159][Open] [patch] use rb_fstring for internal strings — "tmm1 (Aman Gupta)" <[email protected]>
5 messages
2013/11/26
[#58653] [ruby-trunk - Bug #9170][Open] Math.sqrt returns different types when mathn is included; breaks various gems - this bug can be reproduced in Ruby 1.8 as well — "kranzky (Jason Hutchens)" <JasonHutchens@...>
7 messages
2013/11/28
[#58719] [ruby-trunk - Feature #5446] at_fork callback API — "tmm1 (Aman Gupta)" <[email protected]>
6 messages
2013/11/30
[ruby-core:58202] [ruby-trunk - Feature #9076] New one-argument block syntax: &.
From:
"asterite (Ary Borenszweig)" <ary@...>
Date:
2013-11-06 14:22:09 UTC
List:
ruby-core #58202
Issue #9076 has been updated by asterite (Ary Borenszweig).
alexeymuranov (Alexey Muranov) wrote:
> > Note that in doing `array.map &:to_s` the `do ... end` and curly braces are also missing. However, the `&` signals a block, just as when you do `foo &block`. This is no different than `foo &.something` where, again, the `&` signals a block.
>
> Ary, in `array.map &:to_s` curly braces are missing because there is no literal block definition, the block is the result of the `&` operator applied to a symbol.
I know.
Did you know that you can't do `&:to_s` wherever you want?
irb(main):001:0> &:to_s
SyntaxError: (irb):1: syntax error, unexpected tAMPER
&:to_s
^
irb(main):002:0> a = &:to_s
SyntaxError: (irb):2: syntax error, unexpected tAMPER
a = &:to_s
^
That means, Ruby only recognizes `&<expression>` as the last argument to a call. That also means that the `&` operator can only mean a block, somehow. Similarly, `&.` will mean a block with the semantics I already explained.
>
> The main problem IMO with your proposed syntactic sugar for the common special case is that it adds a completely new syntactic rule to Ruby, and also breaks one or more of existing ones.
No, it doesn't break anything because right now that `&.to_s` gives syntax error, which means that syntax is available for defining new meanings.
Normally in Ruby
>
> <method_name1> <identifier1>.<method_name2>.<method_name3>
>
> means: "call the method named by <method_name2> on the object named by <identifier1> or value returned by the method <identifier1>, then call the method named <method_name3> on the result, then yield the result as the argument to a call of the method named by <method_name1>"
>
> (I am not a specialist, i am not sure i am using all the terms correctly.)
>
> It seems to me that what you are looking for is probably a shorter notation for a one-argument lambda. I personally doubt that there is much space in Ruby syntax to introduce it.
As I said, there *is* space in Ruby syntax for it, precisely because right now it's a syntax error.
>
> Skipping the curly braces does not look to me like a benefit and may make the syntax ambiguous or not flexible.
When you do `map &:to_s` you are skipping the curly braces.
>
> The performance penalty of the `&` operator probably can be worked around by compiling the code.
What do you mean?
I think this can be done by Ruby, yes: just make `a.map &:to_s` be the same as `a.map { |x| x.to_s }` by the parser... I think they are discussing similar things to do related to frozen strings.
----------------------------------------
Feature #9076: New one-argument block syntax: &.
https://bugs.ruby-lang.org/issues/9076#change-42783
Author: asterite (Ary Borenszweig)
Status: Feedback
Priority: Low
Assignee:
Category: core
Target version: Next Major
Hello,
I'd like to introduce a new syntax for blocks that have one argument.
Currently you can do this:
[1, 2, 3].map &:to_s
With the proposed syntax this will be written as:
[1, 2, 3].map &.to_s
Instead of ":" we use a ".".
The idea is that this new syntax is just syntax sugar that is expanded by the parser to this:
[1, 2, 3].map { |arg| arg.to_s }
This new syntax allows passing arguments:
[1, 2, 3, 4].map &.to_s(2) #=> ["1", "10", "11", "100"]
It also allows chaining calls:
[1, 10, 100].map &.to_s.length #=> [1, 2, 3]
You can also use another block:
[[1, -2], [-3, -4]].map &.map &.abs #=> [[1, 2], [3, 4]]
Pros:
- Doesn't conflict with any existing syntax, because that now gives a syntax error, so it is available.
- Allows passing arguments and chaining calls
- It's *fast*: it's just syntax sugar. The "&:to_s" is slower because the to_proc method is invoked, you have a cache of procs, etc.
- It looks ok (in my opinion) and allows very nice functional code (like the last example).
Cons:
- Only supports one (implicit) argument. But this is the same limitation of "&:to_s". If you want more than one argument, use the traditional block syntax.
- It's a new syntax, so users need to learn it. But to defend this point, users right now need to understand the &:to_s syntax, which is hard to explain (this calls the "to_proc" method of Symbol, which creates a block... vs. "it's just syntax sugar for")
What do you think?
We are using this syntax in a new language we are doing, Crystal, which has a syntax very similar to Ruby, and so far we think it's nice, simple and powerful. You can read more about it here: http://crystal-lang.org/2013/09/15/to-proc.html
--
http://bugs.ruby-lang.org/