I’ve finally started to work on my next blogpost: Why algebraic datatypes are “algebraic,” explained.
Proofs are done[§], I need to actually write the explanation now x).
Another nice lemma to prove :
α * (β + γ) == α * β + α * γ.
Oh, and also, list α == unit + α * list α
And… non_empty_list α == α * list α
This one was tricky to prove (I wanted to prove it by rewriting, but couldn’t ): )
Ltac can be used to do fun tricks, like computing the type of a fold function for any given datatype, as long as we can provide the “canonical form” (like unit + a * list a for lists)
@na C’est avec ce genre de tricks qu’on peut générer des fold automatiquement pour n’importe quel dataype :D
@charlag Yeah. Explaining it, like, really explaining it for other to get it will be challenging x).
@lthms hey lthms! eager to read it, your blog got me interested in Coq, especially its article on the formalization of a stack!
@jco glay you like my articles! Although I am not sure to know which one you are referring to when you mention stack formalization tbh!
@lthms yeah it was more about annotating functions with their specification, taking the exemple of a list or something like that...
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