21 lines
1.0 KiB
Plaintext
21 lines
1.0 KiB
Plaintext
module Eval where
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open import Agda.Builtin.Bool
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open import Agda.Builtin.Maybe
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open import Agda.Builtin.Nat
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open import Data.Nat.DivMod using (_/_)
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open import Parse
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evalBin : Result BinExpr → Result Nat
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evalBin (emit nothing rem) = emit↑ rem
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evalBin (emit (just (bin (Oper o) (Digit a) (Digit b))) rem) with o
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... | '+' = emit↓ (a + b) rem
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... | '-' = emit↓ (a - b) rem
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... | '*' = emit↓ (a * b) rem
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... | '/' with (b == zero)
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... | false = emit↓ (a / (suc (b - 1))) rem -- todo: why -1 tho
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... | true = emit↑ rem
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evalBin (emit (just (bin (Oper o) (Digit a) (Digit b))) rem) | _ = emit↑ rem
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evalBin (emit (just (bin _ _ _)) rem) = emit↑ rem |