Fix type of (- x) #1004
Fix type of (- x) #1004
Conversation
cptypes was just copying the type from x to (- x). Use predicate-close/plus to get a closed set that includes the result.
burgerrg
left a comment
burgerrg
left a comment
There was a problem hiding this comment.
Thank you for this fix!
release_notes/release_notes.stex
Outdated
| The type recovery pass has improved support for \scheme{exact}, \scheme{inexact}, | ||
| and similar functions. | ||
|
|
||
| Fix wrong type of \scheme{(- x)}, in particular when \scheme{x} is \scheme{(most-negative-fixnum)}. |
There was a problem hiding this comment.
A bug that incorrectly determined the type of \scheme{(- x)} when \scheme{x} is \scheme{(most-negative-fixnum)} was fixed.
There was a problem hiding this comment.
I added "in particular", because it can get the wrong type in other cases. (most-negative-fixnum) is the easiest one.
After a while, I got this:
> (expand/optimize '(lambda (x) (when (or (not x) (eqv? x 4))
(let ([y (- x)]) (list y y)))))
the result is (list 4 4) instead of (list -4 -4).
There was a problem hiding this comment.
Good find!
A bug that incorrectly determined the type of \scheme{(- x)} in some cases has been fixed.
There was a problem hiding this comment.
What about this?
A bug that in some cases incorrectly determined the type of \scheme{(- x)} has been fixed.
or just
A bug that incorrectly determined the type of \scheme{(- x)} has been fixed.
gus-massa
force-pushed
the
25-12-FixMinus
branch
from
4627aa0 to
ee6cf3d
Compare
2 participants
cptypes was just copying the type from
xto(- x). Usepredicate-close/plusto get a closed set that includes the result.Is it possible to try to get a more precise type for the result, like in the
(+ x)case, but I think it's better to fix the bug now and improve the code later.Thanks to @wtakuo for the bug report in Racket #5408 and @mflatt for minimizing it to code in Chez Scheme.