Redeclaring ALIAS

[matchy]

Perhaps there a way to clear the ALIAS for now. Maybe I'm doing it wrong but ALIAS redeclarations don't pass outside a for integer loop.

Code (glbasic) Select Expand


alias_test()
FUNCTION alias_test:
LOCAL arr[], als[], id
DIM arr[2]
FOR id = 0 TO 1
ALIAS ar AS arr[id] // 'ar' can be redeclared and compiled in FOR integer loop :)
DEBUG "For " + id + " passed.\n"
NEXT
DIM als[2]
ALIAS ar AS als[0]
DEBUG "Alias 0 passed.\n"
ALIAS ar AS als[1] // but can't be re-declared for compiling outside loop :(
DEBUG "Alias 1 passed.\n"
ENDFUNCTION


[kanonet]

If you define a variable inside a loop (or an if) it just exist inside this loop. So if you reach NEXT your alias gets deleted, thats why you can define it again without problem in next loop or after the loop. Its the same for LOCAL and ALIAS.

[matchy]

So there's no way to delete or clear it for reuse outside a loop then. 

[Kitty Hello]

uhm... it's a variable like any other. The only exception is, that it can't be unassigned.

Code (glbasic) Select Expand


ALIAS poo AS hotdog
FOR i=0 to 5
   poo = hotdog_factory[i] // point to any in the factory
NEXT
// poo now points to the hotdog_factory[5]
poo = hotdog // point to the original thing again.


Or did I misunderstand your question?

[kanonet]

Im very sure this is wrong.

poo = hotdog_factory

This doesnt move the pointer to hotdog_factory, it just copies the value.
Or are im wrong with this?

[edit] WRONG - see later!

[matchy]

I not trying to understand how it works,  I'm trying to find an alternative to repeated setting that are not in a for loop and parameters can be copy and pasted across same aliases such as a simplified version of this where ar0, ar1, ar2 should use the alias name ar: 

Code (glbasic) Select Expand


ALIAS ar0 AS als[0]
al0.a = 1 // i can't quickly copy and paste interchanging with other ar. named aliases of the same type this way.
al0.b = 2
al0.c = 3
al0.x = 4
al0.y = 5
al0.z = 6

ALIAS ar1 AS als[1]
al1.a = 1
al1.b = 2
al1.c = 3
al1.x = 4
al1.y = 5
al1.z = 6

ALIAS ar2 AS als[2]
al2.a = 1
al2.b = 2
al2.c = 3
al2.x = 4
al2.y = 5
al2.z = 6


[Kitty Hello]

Do you want this?

Code (glbasic) Select Expand


ALIAS prt_a AS als[0]
ptr_a.a = 1
ptr_a.b = 2

prt_a AS als[1]
ptr_a.a = 1
ptr_a.b = 2

FOREACH p in als[]
   DEBUG "a"+p.a+" b:"+p.b+"\n"
NEXT


@kanonet: The ALIAS command gives you a POINTER!! (reference to be precise) to anything. So if you change the alias'ed value, whatever it points to will be changed. This is the same with the FOREACH variables.
And this is why it's so important _NOT_ to REDIM, DIM, DIMPUSH, DIMDEL an array while you are using an ALIAS to any of its childs. If the array internally will reallocate, your ALIAS pointer will screw up and you will be happy if the program only crashes. Mostly it will overwrite random memory.

[kanonet]

@kitty i know. Thats why i said 'poo = hotdog_factory' in your example does not create a new pointer, it just copys the value from hotdog_factory to the location where the pointer points at (In this case hotdog).
Or to make it more clear:

Code (glbasic) Select Expand

LOCAL a, b
ALIAS c AS a
a = b
is not the same like

Code (glbasic) Select Expand

local a, b
ALIAS c AS a
ALIAS c AS b
And of cause its good, that its not the same. But would be nice, if the 2nd one would be possible and not give an compiler error.

[matchy]

Yes, that's what I was hoping for. Again, it's really just about the editing. You know, I could just use individual dummy loops then as this works: 

Code (glbasic) Select Expand


ALIAS ar AS als[0]
DEBUG "Alias 0 passed.\n"

FOR id = 1 TO 1
ALIAS ar AS als[id]
DEBUG "Alias 1 passed.\n"
NEXT

FOR id = 2 TO 2
ALIAS ar AS als[id]
DEBUG "Alias 2 passed.\n"
NEXT


[Kitty Hello]

I really don't understand your problem, matchy.

What's wrong with:

Code (glbasic) Select Expand


FOR id = 1 TO 2
   ALIAS ar AS als[id]
   DEBUG "ALias "+id+" passes\n"
NEXT


[matchy]

In an absolute sense, an example command would be like SET ar = NOTHING, but it not a problem as much as I use it. 

There are cases where I need to set values for a type array that are different for each index, thus not done in a loop. When I have many of these, like over ten I am aliasing ar1, ar2, etc... and it seems pointless. The second example shows probably what I should be doing. 

Code (glbasic) Select Expand


ALIAS ar1 as arr[0]
ar1.x = 1
ar1.y = 2
ar1.z = 3
... // type could have over ten ar.w ar.h ar.l etc...
ALIAS ar2 AS arr[9]
ar2.z = 4
ar2rgb = 0xffff
...


Code (glbasic) Select Expand


FOR i = 0 to 9
ALIAS ar AS arr[i]
SELECT i
  CASE 0
   ar1.x = 1
   ar1.y = 2
   ar1.z = 3
   ...
  CASE 9
   ar2.z = 4
   ar2rgb = 0xffff
ENDSELECT
NEXT


[Kitty Hello]

Ahhhh! I see!
You want to Re-alias. I never thought of this. I can make such a command.

[matchy]

Are we witnessing the design birth of new command?

REALIAS