Inconsistent behavior of deref in closure Topic is solved

[aseiot]

I find %VAR% is not work consistently in closures.

Code: Select all

F(){
	X := 100
	Y := "X"

	TEST_DEREF(){
		MsgBox %Y% ; suppose to 100, actually empty
	}

	TEST_DEREF()

}

F()

If we do some operation before deref, it work as expected.

Code: Select all

F(){
	X := 100
	Y := "X"

	TEST_DEREF(){
		ANYTHING := X ; do any operation before deref
		MsgBox %Y%	; 100 as expected.
	}

	TEST_DEREF()

}

F()

[Helgef]

This behaviour is documented and works a expected,

Dynamic variable references inside a nested function can resolve to variables from the outer function only if the nested function (or one of its own nested functions) also contains a non-dynamic reference to the variable.

If we do some operation before deref, it work as expected.

The sufficient operation is referring to the variable, non-dynamically. (X) alone is enough, and need not be executed ,eg,

Code: Select all

TEST_DEREF(){
	MsgBox %Y% ; 100
	return
	(X)
}

Cheers.

Edit: english

[aseiot]

Thanks for explanation! Cheers.

[lexikos]

The set of "free variables" available to closures is intentionally restricted (based on what references can be discovered at load time) so that the function can be allowed to clear its other local variables when it returns. Aside from generally being conservative, this avoids creating circular references in some cases, such as:

• when the function stores a reference to a closure in a local variable,
• when the function stores a reference to a closure in an object referred by a local variable, such as this in a method,

... but doesn't refer to that variable within any closures.

A circular reference would prevent the closure, all associated free variables, all objects referred by those variables and so on, from being freed until the circle is broken. Breaking a circular reference is harder for closures than for objects because the variables are not accessible from outside.