Re: Re: PATCH: anonymous functions in PHP

On Dec 17, 2007, at 10:30 PM, Larry Garfield wrote:

I'm assuming that making the function above GC-able would be a herculean task at this point, based on previous comments, but I do not actually know myself.

Hi Larry, Let me use a different example than yours. function getAdder($x) { return function ($y) {

    lexical $x;
    return $x + $y;

} } $plusFive = getAdder(5); $plusTen = getAdder(10); echo $plusFive(4); // 9 echo $plusTen(7); // 17 If the closure definition (and thus getAddr) returns a string representing an anonymous function name, then there is no where to hold the enclosing variable $x and no way to know when to free it. Notice that in this example, we have two different enclosing contexts, one where $x is 5 and one where $x is 10. If we introduce a new variable type, a new kind of zval, then internally, that variable can hold: 1) A reference to the local variables of getAddr. (here $x) 2) A reference to $this if the closure is declared in a method 3) A reference to the opcodes of the compiled anonymous function. The opcodes for the closure would be compiled and squirreled away when the script is compiled. When getAddr is executed, a zval would be created that holds the reference to the enclosing locals and a reference to the proper opcodes. Note that $plusFive and $plusTen would hold two different zvals, one for each invocation of getAddr, but that both would refer to the same opcodes structure. When a codeblock zval is executed, such as at $plusFive(4), the enclosing context can be passed to the anonymous function function to make the lexical $x statement bind to the proper variable. When the zval in $plusFive reaches zero references, it can subsequently free its references to the local variables of getAddr. As far as I can see, no herculean garbage collection or reference counting is required. Adding a new kind of zval? Perhaps that's Herculean. I don't know. I hope I've gotten my zval terminology right. Best Regards, Jeff