Re: are there implementation reasons for not providing a break statement in an imperative language?

"Richard Tobin" <richard@cogsci.ed.ac.uk> wrote in message
> August Karlstrom <fusionfile@gmail.com> wrote:
>
>>With no break statements you will know that the loop condition will be
>>false when the loop has finished. This makes it easier to reason about
>>the correctness of a program.


(I admit I know nothing about proving correctness of programs. How
exactly do you go about it? Who or what is to judge whether a program
is correct; is there some sort of specification to compare against?
And if so, how do you know the specification is correct...?)


> A break can trivially be removed by a simple source transformation:
>
> while(condition) {
> pre;
> if(something)
> break;
> post;
> }
>
> boolean stop = false;
> while(!stop && condition) {
> pre;
> if(something)
> stop = true;
> if(!stop)
> post;
> }


This is trivial if the conditional break statement is at the top
level. If the breaks are deeper down then it's not so simple.


--
Bartc

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