FoldRight fixes for Monoid/Semigroup#128
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7h3kk1d merged 1 commit intopalatable:masterfrom May 1, 2023
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- Semigroup::foldRight had parameters flipped - Monoid::foldRight was accumulating the accumulator from the left. This has been fixed but the identity is now being used as a starting accumulator. Otherwise, the evaluation order is unchanged. - Changed ExplainFold parameter name since accumulator can be in either position
jnape
approved these changes
Apr 27, 2023
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Addressing #127
Sidenote
Monoid::foldMapseems to be where short-circuiting is currently implemented. Something that was going to be addressed in the incomplete https://github.com/palatable/lambda/pull/122/files. For obvious reasons, it doesn't seem to address semigroups that should short-circuit. In addition, it has some odd behavior forMonoid::foldRight. For example the function application will now matchSemigroup::foldRight, butand().foldRight(true, repeat(false)).value()does not short circuit with the current implementation ofMonoid::foldRight. I'm tempted to removefoldLeft/foldRightfromMonoidand add alazilyApplytoSemigroupthat would allow for users to override for short-circuiting behavior.