I would not be as pessimistic about the potential uses of the do-while construction, myself. It is just about the only elegant way of coding blocks that must have at least a single pass of execution, and where various assessments can short-circuit the logic, falling through.
Consider the example of prompting a user to input a value for a variable. The code in while() format might be:
<?php
$result = null ;
while( $result === null )
{
print "Gimme some skin, bro!> ";
$result = trim( fgets( $stdin ) );
if( $result === '' )
$result = null ;
}
?>
Well, that works. Lets try it in do-while format:
<?php
$result = '';
do {
print "Gimme some skin, bro!> ";
$result = trim( fgets( $stdin ) );
}
while( $result === '' );
?>
See how it just "reads better"? You say to yourself, "set up $result, print a message, get a response, and continue do to that while the nincompoop fails to enter anything."
Likewise, that "Advanced C" programming example turns out to be the elegant "no goto" way to run through exceptionally involved pieces of block-logic, with a trivial 'break' able to get one all the way past all the unnecessary code in one fell swoop.
For just about every other 'while()' block application, it shouldn't be used. While() is what we expect, and while() is what we should use ... except when the surprisingly common "but we have to do it at <i>least once</i>" criterion pops up its pretty head.
rlynch AT lynchmarks DOT com
