Introducing multiple if()… statements

The switch statement tests a single value. Could we have done this another way? Yes—with the if()… else if()… else if()… else… construct. We could have written the calc() function using multiple if()… else… statements, in this way:

double calc( double operand1 , double operand2 , char operator )  {
  double result = 0.0;

  printf( "%g %c %g = " , operand1 , operator , operand2 );
  if( operator == '+' )
      result = operand1 + operand2;
  else if( operator == '-' )
      result = operand1 - operand2;
  else if( operator == '*' )
      result = operand1 * operand2;
  else if( operator ==  '/'
      if( operand2 == 0.0 ) {
        printf( "*** ERROR *** division by %g is undefined.\n" ,
                operand2 );
        return result;
      } else {
        result = operand1 / operand2;
      }
  else if( operator == '%')...