98 lines
3.9 KiB
Plaintext
98 lines
3.9 KiB
Plaintext
module Parse where
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open import Agda.Builtin.Char
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open import Agda.Builtin.List
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open import Agda.Builtin.Maybe
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open import Agda.Builtin.Nat
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open import Agda.Builtin.String
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open import Expr
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open import Util
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record Result (A : Set) : Set where
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constructor emit
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field
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res : Maybe A
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rem : List Char
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showResult : {A : Set} → (A → String) → Result A → String
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showResult f (emit (just r) _) = primStringAppend "result: " (f r)
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showResult f (emit nothing rem) = primStringAppend "remainder: " (primStringFromList rem)
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-- take consecutive occurences of a character set
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takeCons : List Char → List Char → Result (List Char)
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takeCons [] r = emit nothing r
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takeCons _ [] = emit nothing []
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takeCons cs (x ∷ xs) with (findCharIndex 0 x cs)
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... | nothing = emit nothing (x ∷ xs)
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-- ... | just n = x ∷ (takeCons cs xs)
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... | just n with (takeCons cs xs)
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... | emit nothing rem = emit (just (x ∷ [])) xs
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... | emit (just res) rem = emit (just (x ∷ res)) rem
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parseChar : Char → Token
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parseChar '0' = Digit 0
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parseChar '1' = Digit 1
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parseChar '2' = Digit 2
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parseChar '3' = Digit 3
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parseChar '4' = Digit 4
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parseChar '5' = Digit 5
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parseChar '6' = Digit 6
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parseChar '7' = Digit 7
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parseChar '8' = Digit 8
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parseChar '9' = Digit 9
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parseChar ',' = Delim ','
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parseChar '=' = Oper '='
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parseChar '+' = Oper '+'
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parseChar ' ' = Skip ' '
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parseChar _ = Term
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parseNat : Maybe Nat → List Char → Result Nat
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parseNat a [] = emit a []
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parseNat a (x ∷ xs) with parseChar x
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... | Digit n = parseNat (just (((default 0 a) * 10) + n)) xs
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... | Skip c = parseNat a xs
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... | _ = emit nothing xs
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digits : List Char
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digits = primStringToList "0123456789"
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takeNat : List Char → Result Nat
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takeNat s with takeCons digits s
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... | emit nothing rem₁ = emit nothing rem₁
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... | emit (just xs) rem₁ with parseNat nothing xs
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... | emit nothing rem₂ = emit nothing rem₁
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... | emit (just n) rem₂ = emit (just n) rem₁
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takeOper : List Char → Result Token
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takeOper s with takeCons ('+' ∷ []) s
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... | emit nothing rem = emit nothing rem
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... | emit (just []) rem = emit nothing rem
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... | emit (just (x ∷ xs)) rem with parseChar x
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... | Oper o = emit (just (Oper o)) rem -- todo: what about xs?
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... | _ = emit nothing rem -- todo: loop here?
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-- we know operators are a single char, so xs must be empty, but anything left there should be attached to rem?
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data BinExpr : Set where
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bin : Token → Token → Token → BinExpr
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evalBin : Result BinExpr → Result Nat
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evalBin (emit nothing rem) = emit nothing rem
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evalBin (emit (just (bin (Oper '+') (Digit a) (Digit b))) rem) = emit (just (a + b)) rem
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evalBin (emit (just (bin _ _ _)) rem) = emit nothing rem
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takeBin : List Char → Result BinExpr
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takeBin s with takeNat s
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... | emit nothing rem₁ = emit nothing s
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-- ... | emit (just res₁) rem₁ = emit (just (bin (Oper '+') (Digit res₁) (Digit res₁))) rem₁
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... | emit (just res₁) rem₁ with takeOper rem₁
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... | emit nothing rem₂ = emit nothing rem₁
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-- ... | emit (just oper) rem₂ = emit (just (bin oper (Digit res₁) (Digit res₁))) rem₁
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... | emit (just oper) rem₂ with takeNat rem₂
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... | emit nothing rem₃ = emit nothing rem₁
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... | emit (just res₃) rem₃ = emit (just (bin oper (Digit res₁) (Digit res₃))) rem₃
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takeLine : List Char → List (Result BinExpr)
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takeLine s = map takeBin (split ('\n' ∷ []) s)
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