Re: pureity of closures

[Meta via Digitalmars-d]

On Monday, 30 March 2015 at 13:18:44 UTC, Dicebot wrote:

On Sunday, 29 March 2015 at 12:29:13 UTC, Stefan Koch wrote:

On Friday, 27 March 2015 at 17:47:26 UTC, H. S. Teoh wrote:

What I'm more concerned about is whether the current compiler

implementation may accidentally allow leakage of the pure function's

internal context, which would break purity.


T

please explain your reasoning with a bit of example code.
I am not sure if I get where/when impurity would be introduced.

void delegate() metafoo() pure
{
    int x;
    return () { x = 42; }; // now stack frame of pure function
                           // is available externally
                           // no idea what may happen
}

Maybe even better:

void delegate() metafoo pure
{
    int x;
    if (x > 0)
    {
        return () => x -= 1;
    }
    else
    {
        return () => x += 1;
    }
}