#include <stdio.h>



int main( int argc, char *argv[] )
{
   double a, b;

   a = 4.0;

   b = square( a );  // Make implicit function prototype assumption...
		     // GNU C assumes:    int square(double)

   printf("a = %f, b = %f\n", a, b);
}

// Try chaning the definition of square to:
//
//         double square( double x )   <--- compile error
//         double square( int x )      <--- compile error
//         int square( int x )     <===== Compile, but wrong
//         int square( double x )  <===== product 
//
// and compile...

double square( double x )                  
{
   double r;        // Define a local variable         

   r = x * x;       // Statement

   return ( r );    // Return statement
}