🚀 go-pugleaf

On 01 Apr 1996 10:39:46 PST, martin@kcbbs.gen.nz (Martin D Kealey)
wrote:

>What are needed (to allow some function calls to be optimised
>away) are two new keywords:
>
>  * "clean" which guarantees that the function doesn't modify
>    objects that can only be reached as or through names
>    in an outer scope - and in turn will not call any non-clean
>    functions; and
>
>  * "pure" which guarantees that the function does not depend on
>    the value of any outer scope object - and in turn will not
>    call any non-pure function;
>
>To be fully useful, a function would be declared with both of
>these attibutes and with all pointer or reference parameters
>(including "this") declared "const".
>
>Anyone care to put this forward, or has it been discussed before?

Assuming you allow 'pure' and 'clean', the compiler would then have
to check to make sure your functions were in fact 'pure' and 'clean'.
If the compiler could do such checking as part of its array of
optimizations, why not just do it for every function as
part of a general optimization step?  If the compiler were to do
no checking for the adherence to 'pure' and 'clean' modifiers, then
such modifiers would essentially be a gentleman's contract.  Such
a "contract" could be freely violated with potentially disastrous
results; essentially making 'pure' and 'clean' meaningless.

Jason
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