Avoid incorrect tranformation in + and - in cptypes #1012
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Avoid transforming an expression like `(+ -inf.0 x)`, where `x` is known to be real, into `(fl+ -inf.0 (real->flonum x))` in case `x` is a bignum that would be converted into `+inf.0`. With this incorrect tranformation the result is `+nan.0` instead of `-inf.0`.
mflatt
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Feb 1, 2026
release_notes/release_notes.stex
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| The compiler avoid transforming an expression like \scheme{(+ -inf.0 x)} where | ||
| \scheme{x} is known to be real, into \scheme{(fl+ -inf.0 (real->flonum x))} | ||
| in case \scheme{x} is a bignum that is tranformed into \scheme{+inf.0}. |
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"avoid" -> "avoids", maybe a comma before "where", and "tranformed" (missing an "s") -> "converted" or maybe "would be converted"
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Fixed. Also fixed the commit message that had similar problems.
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In expressions like
(+ -inf.0 x), wherexis known to be real, it's not possible to transform it into(fl+ -inf.0 (real->flonum x))in case x is a bignum that is transformed into+inf.0.The problem with this incorrect transformation the result is
+nan.0instead of-inf.0. So I added more restrictions to check before this transformation is applied.Backstory: I was brute-force-testing
div,mod, and a few more similar primitives, with combinations of two numbers from a long list of interesting tricky numbers. Then I decided to add+and-to the list of primitives to test. I found thathad a different result when
cptypeswas applied beforecp0.