Re: Storage management, was Compiler writers will love this language

On 2 Jul 2003 00:40:16 -0400, Gene Wirchenko posted:
>>It smells a bit undecidable to me. At least for the complete case, I think
>>this reduces to the halting problem.
>>
>> Object foo(Object x, Object y) {
>> if (halts(x)) {
>> return y;
>> } else {
>> return x;
>> }
>> }
>>
>>When do you release x's memory?
>
> if branch: yes, else branch: no.
>
> Your code would make sense to me if the return values were
> switched. Is that what you meant, or am I missing something?


The idea is that you can't statically determine whether or not you branch.
If you could, you'd have solved the halting problem.


x represents a (program,input) pair, and halts(x) tells you whether the
program given ever stops with the given input. Now I think about it a bit
harder, I've made it needlessly subtle: I'm using x in two ways, as the
program to be tested _and_ the object to be freed.


To be a bit more verbose:


Object foo(Program p, Input i, Object x, Object y) {
if (halts (p,i)) {
return x;
} else {
return y;
}
}


and also assuming that there are no other references to the objects x and y.


mrak

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