3a408e0e54
This PR changes the signature of `Array.get` to take a Nat and a proof, rather than a `Fin`, for consistency with the rest of the (planned) Array API. Note that because of bootstrapping issues we can't provide `get_elem_tactic` as an autoparameter for the proof. As users will mostly use the `xs[i]` notation provided by `GetElem`, this hopefully isn't a problem. We may restore `Fin` based versions, either here or downstream, as needed, but they won't be the "main" functions. --------- Co-authored-by: David Thrane Christiansen <david@davidchristiansen.dk>
45 lines
1.2 KiB
Text
45 lines
1.2 KiB
Text
-- Some of these tests made more sense when we had a
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-- derive_functional_induction command.
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#check doesNotExist.induct
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def takeWhile (p : α → Bool) (as : Array α) : Array α :=
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foo 0 #[]
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where
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foo (i : Nat) (r : Array α) : Array α :=
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if h : i < as.size then
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let a := as.get i h
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if p a then
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foo (i+1) (r.push a)
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else
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r
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else
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r
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termination_by as.size - i
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-- Checks the error message when the users tries to access the induct rule for the wrong function
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-- (before we used reserved names for this feature we did give a more helpful error message here)
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#check takeWhile.induct
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#check takeWhile.foo.induct
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-- this tests the error we get when trying to access the induct rules for
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-- a function that recurses over an inductive *predicate* (not yet supported)
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inductive Even : Nat → Prop where
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| zero : Even 0
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| plus2 : Even n → Even (n + 2)
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def idEven : Even n → Even n
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| .zero => .zero
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| .plus2 p => .plus2 (idEven p)
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#check idEven.induct
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-- this tests the error we get when trying to access the induct rules for
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-- a function that recurses over `Acc`
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def idAcc : Acc p x → Acc p x
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| Acc.intro x f => Acc.intro x (fun y h => idAcc (f y h))
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#check idAcc.induct
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