From: Stephen Waits <steve@...>
Date: 2005-12-13T15:48:36+09:00
Subject: Re: Idiom wanted: do-while

Mark Ericson wrote:
> 
>> Because it's hard for users to tell
>>
>>   begin <code> end while <cond>
>>
>> works differently from
>>
>>   <code> while <cond>
>>
> in what ways are they different?  Any code examples to show the difference?

Andy already answered, but I thought I'd take my shot at it too.

     begin <code> end while <cond>

is guaranteed to execute <code> at least one time; whereas,

     <code> while <cond>

may never execute <code> because it is exactly equivalent to

     while <cond> <code>

in the same way that

     if <cond> <code>

is equivalent to

     <code> if <cond>

The whole begin/end thing is definitely unnecessary, and can (and 
frequently does) become a source of confusion; it's a good thing that 
it's going away.  The sooner the better.

--Steve