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snowleopard / alga

Algebraic graphs
MIT License
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Implement induce via induceJust #271

Closed snowleopard closed 3 years ago

snowleopard commented 3 years ago

Implementing induce as induce p = induceJust . fmap (\a -> if p a then Just a else Nothing) seems to pass inspection tests. My understanding is that this means fmap fuses nicely with the induceJust, and so using this simpler definition comes at no runtime cost.

@nobrakal Could you have a look?

nobrakal commented 3 years ago

I just hand-checked it to be sure: it works :tada: You understood everything correctly, fusing happens as expected. GHC is impressive!

snowleopard commented 3 years ago

@nobrakal Great, many thanks for double-checking! That's a very nice example of graph fusion in action :)