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Don't use float equality for AST comparisons #1238

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Don't use float equality for AST comparisons #1238

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@Clyybber Clyybber commented Mar 13, 2024 •
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Summary

Float equality lacks the substitution nor reflexivity properties usually expected from an equality operator, so it's not correct to use float equality in AST comparisons. This PR changes it so that they are compared for bit equality.

Details

  • 0.0 and -0.0 are not being considered equal by the compiler anymore (see added tests)
  • trees.exprStructuralEquivalentStrictSym and it's only usage in sem/semfoldnim have been removed

TODO

These could be included in this PR or be sepeate PRs:

  • Remove analysis for floats from sem/guards.nim sem: remove float analysis from sem/guards #1240
  • Ensure all float constants can round-trip as literals in the renderer
  • Ensure that the backend generate float constants bit equal
  • Issue a warning or hint when float equality doesn't match cmpFloatRep

@Clyybber Clyybber mentioned this pull request Mar 14, 2024
Merged
@Clyybber
Move cmpFloatRep from vm/vmgen to ast/trees
ef0c454
@Clyybber
Use cmpFloatRep instead of float equality in sem/patterns
ce05601
@Clyybber
Add comment about float equality in sem/guards
835d0fa
@Clyybber
Use cmpFloatRep in trees.exprStructuralEquivalentStrictSymAndComm
87617b4 
instead of sameFloatIgnoreNan
@Clyybber
Use cmpFloatRep in trees.exprStructuralEquivalentStrictSymAndComm
6217eb1 
instead of sameFloatIgnoreNan. This does not cause
a change in behaviour because only nkNilLit or nkSym nodes
reach its only usage in sem/semfold for mEqProc
@Clyybber
Don't use exprStructuralEquivalentStrictSym in sem/semfold
e64f674 
and remove it from ast/trees as it's now deadcode
@Clyybber
Use cmpFloatRep in trees.exprStructuralEquivalent
52a8928 
instead of sameFloatIgnoreNan and update and add tests
to reflect this change in semantics.
@Clyybber
Remove trees.sameFloatIgnoreNan as it's deadcode
aad0275 
and update comments
@Clyybber
Add comment about guards.sameTree invalid float equality
c8b2d82
@Clyybber
Undo whitespace change
2cfd55a
@Clyybber
exprStructuralEquivalentStrictSymAndComm: Don't ignore nkType type eq…
06f6310 
…uality
@Clyybber Clyybber mentioned this pull request Mar 15, 2024
Merged
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