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

In article 11-01-055,
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.


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;
}


Is this easier to reason about? Not for a computer: it could do the
transformation itself. A human doing certain particular kinds of
reasoning might find it easier, but a human just reading the program
is likely to find it less clear.


A programmer may be able to find a more natural alternative than the
one above, but even if he does the language has prevented him from
expressing his intention in the obvious way.


-- Richard

Return to the comp.compilers page.
Search the comp.compilers archives again.