8 replies to this topic

[HotKeyIt]

Try this:

r(ByRef a) {

  static var

   if !isobject(a)

      msgbox % a

   else

      for k, v in a

         r(var:=v)

}

x := [10,20,30,[100,200,300]]

r(x)

[Lexikos]

Please note:

Although a function may call itself recursively, if it passes one of its own local variables or non-ByRef parameters to itself ByRef, the new layer's ByRef parameter will refer to its own local variable of that name rather than the previous layer's. However, this issue does not occur when a function passes to itself a global variable, static variable, or ByRef parameter.
Source: Functions - ByRef

Also note you do not need to use ByRef to pass an object reference. ByRef should only be used if you need to assign another value or object to the variable. It means "pass variable by reference".

[Lexikos]

if I can call r(a[k]) using recursion why I can't call r(v).

ByRef indicates that the function accepts a reference to a variable. a[k] is not a "variable" in the strict context of the documentation or implementation, and therefore not passed by reference.

[AHK_L 60+]: If something other than a modifiable variable is passed to a ByRef parameter, the function behaves as though the keyword "ByRef" is absent. For example, Swap(A_Index, i) stores the value of A_Index in i, but the value assigned to Left is discarded once the Swap function returns.
Source: Functions

Internally, a[k] is essentially an element in an array of key-value pairs, where any element could be moved or the entire array could be freed/reallocated at any time. The only safe way to refer to it is to have a reference to the object and a copy of the key (or keys: a[x, y] is also valid). The current "variable reference" or "ByRef" mechanism simply isn't capable of this.

It appears I can't print a memory address of a[k] directly,

The &address-of operator has two functions:


[*:t66xbgb5]Retrieve the address of a variable's string buffer (see below).
[*:t66xbgb5]Retrieve the address of an object.
In the first case, only a plain "variable" reference is accepted. Since a[k] is not a "variable" and does not contain an object, &a[k] will not work. If it contained a string, you could use a.GetAddress(k), but in this case it contains an integer. Like with the element itself (see above), the actual location in memory of this integer can change as other items are added or removed from the object, so retrieving its address is not supported.

I'm surprised that v and var_ak wouldn't be pointing to the same address.

Each variable has its own buffer for storing strings, and therefore an address which is unique to that variable (but can change). VarSetCapacity sets or retrieves the capacity of this buffer.

[HotKeyIt]

Please note:

Although a function may call itself recursively, if it passes one of its own local variables or non-ByRef parameters to itself ByRef, the new layer's ByRef parameter will refer to its own local variable of that name rather than the previous layer's.

So the function you call recrusively has the variable v now in ByRef a, but the v is its local v because previous layer's v has been backed up and cleared due to function call (because it is a local var).

[infogulch]

Since we're using ahk_l, may I suggest passing an object for recursive calls (NOT as ByRef)?

Changes made to the object in deeper recusion levels will still apply to the object in the local var in other recursion levels.