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Re: Suggestion: add do-enddo(condition)

From: Johan Kullstam
Subject: Re: Suggestion: add do-enddo(condition)
Date: 28 Jan 2000 18:03:19 -0500
User-agent: Gnus/5.0803 (Gnus v5.8.3) Emacs/20.4

(Ted Harding) <address@hidden> writes:

> I would be in favour of introducing these forms,
> (a) for convenience,
> (b) because "built-in" implementation would normally be much faster
>     than interpretation of the above implementations.
> However, I suggest it might be better to do the test _before_ executing
> the body -- i.e. if the loop is entered with its exit condition already
> true, then the body would not be executed -- for both 'while'
> and 'until' (since either way round 'until' == 'while not'). 

we *already have* a looper that tests before executing.  while cond
body endwhile.  what we *don't* have (yet) is the other one ---
execute at least once before test.  do body while cond or do body
until cond.

> This would be consistent with the behaviour of the C 'while (cond) body'
> construct, which does it this way (as opposed to the C construct
> 'do body while (cond)' which tests the condition after executing the
> body). The difference is that with the post-test the body is executed
> at least once; with the pre-test it might not be executed at all.
> There are arguments for the merits of either way round, but I think
> that the pre-test form is likely to be the one most often useful.

oh most certainly.  the pre-test will probably remain the most popular
form.  however, the post-test form is surely useful too and should be

J o h a n  K u l l s t a m
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