qsort Funktion

qsort will sort an array of elements. This is a wild Funktion that uses a pointer to another Funktion that performs the required comparisons.

Library:   stdlib.h

Prototype: void qsort(void *base, 
		      size_t num, 
		      size_t size, 
 		      int (*comp_func)(const void *, const void *))

Some explanation.

• void * base

  Is a pointer to the array to be sorted. This can be a pointer to any datatype.

• size_t num

  The number of elements.

• size_t size

  The element size.

• int (*comp_func)(const void *, const void *))

  This is a pointer to a Funktion.

Notes

1. Well... This caused me alot of trouble! Although the prototype above is exactly as shown in the documentation, the last parm kept giving compiler warnings (invalid pointer type) this is the fix.

   	
   Prototype: void qsort(void *base, 
   		      size_t num, 
   		      size_t size, 
    		      (void *) (*comp_func)(const void *, const void *))
   

   does anyone know the answer to this problem??

2. I think void * needs an explanation.

3. And cast aswell

Example program with user input.

O'Reilly 'Using C' example.