From 7e0f021a9aec35fd8e6725e87e3313b101d26f5e Mon Sep 17 00:00:00 2001 From: Tobias Klauser Date: Sun, 27 Jan 2008 11:37:44 +0100 Subject: Initial import (2.0.2-6) --- reference/C/SYNTAX/functions.html | 138 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 138 insertions(+) create mode 100644 reference/C/SYNTAX/functions.html (limited to 'reference/C/SYNTAX/functions.html') diff --git a/reference/C/SYNTAX/functions.html b/reference/C/SYNTAX/functions.html new file mode 100644 index 0000000..1f14822 --- /dev/null +++ b/reference/C/SYNTAX/functions.html @@ -0,0 +1,138 @@ +Functions and passing arguments. + + + + +
+
+

Functions and passing arguments.

+
+
+A function is a block of code that can be executed many times by other +functions or its self. + + +
+

Function Basics.

+You should already understand the concept of functions! If you don't, you +are a sad sad man....

+Might expand on this one day.

+P.S. main() is a function. + +

Declaration.

+Just like variables, all functions have to be +declared before use. Here is an +example. +
+        int add( int, int);
+
+This statement declares a function called add, it has two integer +arguments and returns an integer. + +

Definition.

+The definition is the meat of the +function. Heres an example. + +

Passing values.

+Passing values is known as call by value. You actually pass a copy +of the variable to the function. If the function modifies the copy, the original +remains unaltered. The previous example demonstarted call by value +

Passing pointers.

+This is known as call by reference and is an area worth spending some +time on. We do not pass the data to the function, instead we pass a pointer +to the data. This means that if the function alters the data, the original +is altered.

+

+ Example of passing a pointer to a scalar. +

+ + +C++ has a nice feature called +reference variables +which is a tider +approch to modifing the contents of a passed variable. + + +

Passing Arrays.

+
+ Example of passing a pointer to an integer array. +
+ Example of passing a pointer to a two +dimensional integer array. +
+ Example of passing a pointer to a +character array. +
+ Example of passing a two dimensional +character array. +

Variable number of parms (...)

+ +
+ Example of passing an unknown number +of variables to a function + +
+ Man page for va_start, va_end etc + +

Function recurssion.

+

Returning values.

+ +Normally you would return an 'int', 'char', 'float', or 'double' using this +technic. The obvious time to return a value would be to return a completion +code. +

+Here is an example +

+The contents of 'c' are copied into 'i'. + +

Returning pointers.

+ +Returning values is OK for the data types above but not very practical for +'char *' or structures. For these data types passing pointers can be more +appropriate. When using these pointers it is important to understand the +'static' storage class +otherwise you are going to get some unpredictable +results. + +

+ +

+

+

+ + + + +
+ Top + + Master Index + + Keywords + + Functions +
+
+

+

+
Martin Leslie +

+ + -- cgit v1.2.3-54-g00ecf