Function Parameters
In many books and conversations, the terms parameter
and argument are used interchangably.
The term formal parameter is also used
in discussions about functions. For this discussion,
- parameter or formal parameter
are equivalent and refer to the variable defined in the
function definition.
- argument refers to the variable or expression
passed to the function when the function is called.
The two basic kinds of parameters are "call-by-value" parameters
and "call by reference" parameters.
Call-by-value parameters
Call-by-value parameters are the kind you've been using so far
in all your programming. The call-by-value parameter is a
placeholder into which the value of the corresponding argument
is copied. Note that the corresponding argument may be a variable
or an expression. As the example code from the text below shows,
the call-by-value parameter is actually a local variable and may
be changed within the function without affecting the corresponding
argument in the calling code.
<![CDATA[
//---------------------------------
// File: 04-01.cpp
// Date: 8/20/03
// Author: D. Frey
// Section: n/a
// EMail: frey@cs.umbc.edu
//
// This is a modified version of example 04-01
// from the text, page 135
//----------------------------
#include <iostream>
using namespace std;
// prototypes for functions in this file
double fee(int hoursWorked, int minutesWorked);
int main ( )
{
int hours, minutes;
double bill;
cout << "Welcome to the law office of\n"
<< "Dewey, Cheatham, and Howe.\n"
<< "The law office with a heart.\n"
<< "Enter the hours and minutes"
<< " of your consultation:\n";
cin >> hours >> minutes;
bill = fee(hours, minutes);
cout.setf(ios::fixed);
cout.setf(ios::showpoint);
cout.precision(2);
cout << "For " << hours << " hours and " << minutes
<< " minutes, your bill is $" << bill << endl;
return 0;
}
//--------------------------------------------------
// Function: fee( )
// PreConditions:
// minutesWorked and hoursWorked should be nonnegative
// PostConditions:
// Returns the charges for hoursWorked hours and
// minutesWorked minutes of legal services. Returns
// zero if either parameter is negative
//---------------------------------------------------
double fee (int hoursWorked, int minutesWorked)
{
if (hoursWorked < 0 || minutesWorked < 0)
return 0.0;
const double RATE = 150.00; //Dollars per quarter hour.
int quarterHours;
minutesWorked = hoursWorked * 60 + minutesWorked;
quarterHours = minutesWorked / 15;
return (quarterHours * RATE);
}
]]>
Last Modified: Monday, 28-Aug-2006 10:15:59 EDT