Handle negative values in lexer differently #44
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Change lexer so it does not match negative numbers if there is a variable or a number(letter or digit) behind it
Forgot the "_" and "'" which may be in the variable/digit names
WoWaster
requested changes
Oct 3, 2025
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Is there a reason to use such complicated lexer construction? I'd better simplify lexer with this change rather than complicating it more.
I propose a way similar to OCaml.
At first we generate separate tokens for minus and a number (as Text).
https://github.com/ocaml/ocaml/blob/f024962042c57a257f4367fbadbcb8d3428c3895/parsing/lexer.mll#L552
Then in the parser prepend number with - if we see TokMinus before TokInt.
OCaml then converts string to int during typechecking phase, but we can just read inside parser rule for integer constant.
Now negative values are handled inside the parser. Lexer is changed not to scan negative values.
Danil-Zaripov
commented
Oct 6, 2025
WoWaster
approved these changes
Oct 9, 2025
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Compiler was failing in cases
let f x=x-1, where it would compile it aslet f x = x (-1)treating x as a function, when it should certainly be treated as a number. This was due to a lexer bug.The fix is that lexer only matches negative values if there could not be a variable name(letters, numbers, _, ') or a number behind it.