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30 lines
663 B
Idris
30 lines
663 B
Idris
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data View : List a -> Type where
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Nil : View []
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(::) : (x : a) -> (xs : List a) -> View (x :: xs)
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view : (xs : List a) -> View xs
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view [] = []
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view (x :: xs) = x :: xs
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idL : (xs : List a) -> View xs -> List a
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idL .([]) [] = []
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idL .(x :: xs) (x :: xs) = x :: idL xs (view xs)
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{- Current compile time tree:
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Compile time tree: case {arg:1} of
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Nil {e:0} => case {arg:2} of
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Nil {e:4} => []
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(::) {e:1} {e:2} {e:3} => case {arg:2} of
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(::) {e:5} {e:6} {e:7} => {e:2} :: idL {e:3} (view {e:3})
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-}
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{- With dotted expressions change:
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Compile time tree: case {arg:2} of
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Nil {e:0} => []
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(::) {e:1} {e:2} {e:3} => {e:2} :: idL {e:3} (view {e:3})
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-}
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