Lecture05

Lecture05

• 1.
  Lecture 05 Overloaded Functions and Inline Functions Learn about: Some functions that are not supported in C: - Overloaded - inline functions - default arguments. Ref.: OOP using C++, Joyce Farrel, Thopson Learning 1
• 2.
  Overloaded Functions (page146-148) • Overloaded functions are functions that have similar name but each performs different activities depending on the kind of data sent to the function. • The compiler uses the number of arguments, and their data types, to distinguish one function from another. • Function overloading is not allowed in C. 2/15
• 3.
  Function Overloading Example 1 #include <iostream.h> void repchar(char ch) void repchar(); { for(int j=0; j<20; j++) void repchar(char); cout << ch; void repchar(char, int); cout << endl; } int main() { void repchar(char ch, int n) repchar(); { for(int j=0; j<n; j++) repchar('='); cout << ch; repchar('+', 30); cout << endl; return 0; } } void repchar() Output: { for(int j=0; j<20; j++) ******************** cout << '*'; ==================== cout << endl; +++++++++++++++++++++++++ 3/15 }
• 4.
  Function Overloading Example 2 #include <iostream.h> void show(double val) { cout << "Double: " << val void show(int); << endl; void show(double); } void show(char*); void show(char *val) int main() { cout << "String: " << val { show(12); << endl; show(3.1415); } show("Hello World"); return 0; Output: } void show(int val) Integer: 12 { cout<<"Integer: "<<val Double: 3.1415 << endl; String: Hello World } 4/15
• 5.
  Inline Functions (page143-144) • Functions are good for structured programming but incur runtime overhead. • An inline function is written like a normal function but compiles into inline code which is inserted into the program wherever a function call occurs. • Inline functions are not allowed in C. 5/15
• 6.
  Inline Functions :Overhead : memory : a 10 int main() { func1(10, 20); b 20 : x 30 : func1(40,50); • passing control to the function. : : • placing argument values in a memory. } • returning to proper point in the calling program. void func1(int a, int b) { : • providing a memory for any returned x = a + b; value : } 6/15
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  Inline Functions: Example1 #include <iostream.h> inline void lbstokg(float pounds) { 0.453592 * pounds; } void main() { float lbs; cout<<"Enter weight in pounds: "; cin>>lbs; cout<<"Your weight in kg is " << lbstokg(lbs) << endl; } 0.453592 * lbs 7/15
• 8.
  Inline Functions: Example2 #include <iostream.h> inline double computeGross(double hours, double rate) { return (hours * rate); } void main() { double hrsWorked = 37.5, rateOfPay = 12.45, gross; gross = computeGross(hrsWorked, rateOfPay); cout<<endl<<“Gross pay is “<<gross; } hrsWorked * rateOfPay 8/15
• 9.
  Inline Functions VsMacros • Inline functions are similar to macros declared with the #define directive. The major differences are: – Inline functions are recognized by the compiler. Macros are implemented by a simple text substitution. – Compiler performs type checking on the parameters of an inline function. Macros have unwanted side effects. 9/15
• 10.
  Inline Functions VsMacros Example #include <iostream.h> #define MAX(A,B) ( (A) > (B) ? (A) : (B)) inline int max(int a, int b) void main() { if (a > b) { int result,x,y; return a; x = 23; y = 45; result = MAX(x++, y++); else cout << x << y << "n"; return b; } x = 23; y = 45; result = max(x++, y++); cout << x << y << "n"; } Output from the program: 2447 10/15 2446
• 11.
  Default Arguments (page144 - 146) #include <iostream.h> void compute (int length, int width, int height) { ……….. } void main() { …… compute (12, 7); // cause syntax error } 11/15
• 12.
  Default Arguments (page144 - 146) • A function can be called without specifying all its arguments. • The function declaration must provide default values for those arguments that are not specified. • Default arguments are not allowed in C. 12/15
• 13.
  Default Arguments: Example1 #include <iostream.h> void repchar(char='*', int=20); void main() { repchar(); // print 20 '*' repchar('='); // print 20 '=' repchar('+', 25); // print 25 '+' } Output: void repchar(char ch, int n) ******************** { ==================== for(int j=0; j<n; j++) +++++++++++++++++++++++++ cout << ch; cout << endl; } 13/15
• 14.
  Default Arguments: Example2 #include <iostream.h> void showstring(char *str = "Hello World!") { cout << str << endl; } void main() { showstring("Here's an explicit argument."); showstring(); // in fact this says: // showstring("Hello World!"); } Output: Here's an explicit argument. Hello World! 14/15
• 15.
  Default Arguments: Example3 #include <iostream.h> void example(int, int = 5, float = 6.78); void main() { example(7, 2, 9.3); example(7, 2); example(7); } void example(int x, int y, float z); { cout << x << y << z << endl; } Output: 7 2 9.3 7 2 6.78 7 5 6.78 15/15