15 lines
422 B
Text
15 lines
422 B
Text
class Semiring (R : Type u) extends Add R, HPow R Nat R, Mul R where
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zero : R
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instance [Semiring R] : OfNat R n where
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ofNat := Semiring.zero
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def Nat.cast [Semiring R] (n : Nat) : R := let _ := n = n; Semiring.zero
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@[default_instance high] instance [Semiring R] : HPow R Nat R := inferInstance
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instance [Semiring R] : CoeTail Nat R where
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coe n := n.cast
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variable (R) [Semiring R]
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#check (8 + 2 ^ 2 * 3 : R) = 20
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