choose() function [u524]/Variadic varargs

[EnigmaBot]

(Posted by on the ENIGMA forums)

The choose() gml function isn't implemented in enigma properly. There needs to be a way to have any number of arguments on a range from 2 to the argument limit (which I think in GM is 16?). I'm trying to port a game made by a friend of mine to Linux but can't because of the errors related to his use of the choose() function.

[TheExDeus]

I think it did work before, but I also noticed that it is broken now. Works with only 2 or so arguments.

[fundies]

I had a similar issue with mean when josh switched out the C parser. Probably needs the same fix.

[forthevin]

The bug occurs only when you try using a variable, not a literal, as an argument for the choose function inside a script. Outside a script, or only using literals, choose works correctly.

[EnigmaBot]

(Posted by on the ENIGMA forums)

I can't even believe that's true. I'm afraid to say that fixing this would be finding a needle in a haystack; I'm setting the milestone to enigma-jdi, wherein the mechanism scripts use to access locals will not interfere with the enigma::varargs mechanism. I should apologize now for the delay. As a workaround, try declaring each parameter as a script-local, though it sounds like that might not help.

[RobertBColton]

I have done some regression testing on this issue.
https://www.dropbox.com/s/lil7mdx4eysuhf6/scriptchoosevariable.gm81?dl=0

Create event:

a = 1;
b = 2;
c = 3;

Step event:

if (keyboard_check_released(vk_space)) {
  show_message(choose(a,b,c));
  show_message(choose(1,2,3));
  show_choose_message();
}

show_choose_message() script:

show_message(choose(a,b,c));
show_message(choose(1,2,3));

C:/ProgramData/ENIGMA/Preprocessor_Environment_Editable/IDE_EDIT_objectfunctionality.h:39:43: error: 'a' was not declared in this scope
   show_message(choose((enigma::varargs(), a, b, c)));
                                           ^
C:/ProgramData/ENIGMA/Preprocessor_Environment_Editable/IDE_EDIT_objectfunctionality.h:39:46: error: 'b' was not declared in this scope
   show_message(choose((enigma::varargs(), a, b, c)));
                                              ^
C:/ProgramData/ENIGMA/Preprocessor_Environment_Editable/IDE_EDIT_objectfunctionality.h:39:49: error: 'c' was not declared in this scope
   show_message(choose((enigma::varargs(), a, b, c)));
                                                 ^

[TheExDeus]

It's not only choose, but min, max, median and so on. I have reported this before, most recently here: http://enigma-dev.org/forums/index.php?topic=1860.0
The problem is that the parser doesn't take the correct variable. If you did "var sa = a, sb = b, sc = c" and then choose(sa,sb,sc), then it would work.

[RobertBColton]

@sorlok Do you think you could possibly offer some insight into how this functionality broke? I'm just wondering since you seem really good about offering a new perspective on old issues.

[sorlok]

Well, I'm not sure how it broke, but I think @TheExDeus describes the issue perfectly. The parser doesn't tag variables inside functions correctly. Which means a grueling parser debug to fix this bug.

[RobertBColton]

Hmmm, the problem is I would try to fix it but I don't even know where to start really. It's a part that I am unfamiliar with, but I guarantee it's a simple fix. @JoshDreamland Should offer some clues for where to look.

[TheExDeus]

I doubt this "broke". I think it never worked. I made a topic about this issue in April, but I mentioned it before last year or even a year before that. So as far as I'm aware this was never fixed/implemented.

Basically you need to check variables inside the vararg functions and see if instances has them as locals or if you need to create a temporary one. I guess the problem here is the vararg's (functions with variable number of arguments) which are not properly handled in current parser.

[RobertBColton]

Another workaround discovered in #914 is the following:

var yolo,swag;
swag = self.swag;

[RobertBColton]

I should add that this issue was also a duplicate of #5 which was already a known parser bug.

[RobertBColton]

I should mention too that I think the Wiki article about varargs is outdated.
http://enigma-dev.org/docs/Wiki/Varargs

And just plain choose(1,2,3) in an empty game throws an exception on compile (a Java exception invokeInt) but show_message(choose(1,2,3)); does not.