while
while, do-while, and
for control looping. A statement repeats until the controlling expression
evaluates to false. The form of a while loop is
while(expression)
statement
The expression is evaluated once at the
beginning of the loop and again before each further iteration of the
statement.
This example stays in the body of the
while loop until you type the secret number or press
control-C.
//: C03:Guess.cpp
// Guess a number (demonstrates "while")
#include <iostream>
using namespace std;
int main() {
int secret = 15;
int guess = 0;
// "!=" is the "not-equal" conditional:
while(guess != secret) { // Compound statement
cout << "guess the number: ";
cin >> guess;
}
cout << "You guessed it!" << endl;
} ///:~
The while’s
conditional expression is not restricted to a simple test as in the example
above; it can be as complicated as you like as long as it produces a true
or false result. You will even see code where the loop has no body, just
a bare semicolon:
while(/* Do a lot here */)
;
In these cases, the programmer has
written the conditional expression not only to perform the test but also to do
the
work.
