PRODUCT  :  Borland C++                           NUMBER  :  1548
  VERSION  :  All
       OS  :  All
     DATE  :  October 25, 1993                         PAGE  :  1/2

    TITLE  :  Function pointers and variable length argument lists




  /*
  * This example shows how to use pointers to functions within a
  * variable parameter list.  A type for the function pointer must
  * be defined using 'typedef' in order to use function pointers
  * with a variable parameter list.  The syntax for this is as
  * follows:
  *
  *   typedef <return value> ( *<typename>) ( <Paramater list> );
  *
  * You would use the variable specified by <typename> to declare
  * instances of the function pointer in the same way    that
  * 'int' is used to create instances of integers.  Failing to use
  * the typedef will cause an Expression Syntax Error.
  *
  * See the online documentation on va_arg for more information on
  * using variable parameter list.
  */
  #include <stdio.h>
  #include <stdarg.h>


  /*  Declare a new type: a function taking no parameters,
  *   returning an integer.
  */
  typedef int ( *type ) ( void );

  /* A function which returns the value three.
  */
  int three( void )
  {
      printf( "In function three\n" ) ;
      return 3 ;
  }

  /* A function which returns the value ten.
  */
  int ten( void )
  {
      printf( "In function ten\n" ) ;
      return 10 ;
  }

  /*  Calculate the sum of a 0 terminated list of functions













  PRODUCT  :  Borland C++                           NUMBER  :  1548
  VERSION  :  All
       OS  :  All
     DATE  :  October 25, 1993                         PAGE  :  2/2

    TITLE  :  Function pointers and variable length argument lists




  *  which return integers.
  */
  void sum(char *msg, ...)
  {
      int total = 0;
      va_list ap;
      type func ; // Pointer to the function
      va_start( ap, msg );
      while (( func = va_arg( ap,type )) != 0)
      {
          total = total + func() ; // Compute total
      }
      printf( msg, total ) ;
      va_end(ap);
  }

  int main(void)
  {
      sum( "The total of the functions is %d\n",
      three, ten, 0);
      return 0;
  }


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