Add parentheses to nested comparison expressions

UnderminersTeam / UndertaleModTool

The most complete tool for modding, decompiling and unpacking Undertale (and other GameMaker games!)

GNU General Public License v3.0

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Add parentheses to nested comparison expressions #1813

Closed Jacky720 closed 5 months ago

Jacky720 commented 5 months ago

Description

Minor fix for a bug reported on Discord where the code x -= ((1 + statetime) < (2 + statetime)) < 4 would decompile as x -= (1 + statetime) < (2 + statetime) < 4.

Caveats

Only the possible exceptions where parentheses might be helpful to other, yet rarer, expressions, which would have already been decompiling incorrectly.

Notes

N/A

github-actions[bot] commented 5 months ago

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CST1229 commented 5 months ago

a < b < c is valid GML syntax (it's accepted by GameMaker's compiler), so I think it might be better/saves parentheses to instead allow multiple comparison operators next to eachother in the compiler (like it already is possible with math), which I already did for UTMTCE. Maybe I should PR that.

Jacky720 commented 5 months ago

What does GameMaker's compiler produce in this case? If it's like Python, it would be a < b && b < c, but if it's actually producing (a < b) < c as in turning the first comparison from boolean to number, we should decompile that.

Jacky720 commented 5 months ago

Yeah, I just spun up a dummy project, that's exactly what it's doing. "a < b" is false, 0, and 0 < c. (a < b) < c is the opposite of the code's intent, of course, but consistent with the new decompilation (and the mod tool compiler can handle it).

Miepee commented 5 months ago

Even though it is a compiler bug, let's just always force parattheses for now on. Makes that code way more readable and prevents user bugs.