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(.module:
[lux #- not]
(lux (control [functor #+ Functor]
[apply #+ Apply]
[monad #+ do Monad]
[codec])
(data (collection [list "list/" Functor<List> Monoid<List>])
[product]
["e" error #+ Error])))
(type: #export (Parser s a)
{#.doc "A generic parser."}
(-> s (e.Error [s a])))
## [Structures]
(structure: #export Functor<Parser> (All [s] (Functor (Parser s)))
(def: (map f ma)
(function (_ input)
(case (ma input)
(#e.Error msg)
(#e.Error msg)
(#e.Success [input' a])
(#e.Success [input' (f a)])))))
(structure: #export Apply<Parser> (All [s] (Apply (Parser s)))
(def: functor Functor<Parser>)
(def: (apply ff fa)
(function (_ input)
(case (ff input)
(#e.Success [input' f])
(case (fa input')
(#e.Success [input'' a])
(#e.Success [input'' (f a)])
(#e.Error msg)
(#e.Error msg))
(#e.Error msg)
(#e.Error msg)))))
(structure: #export Monad<Parser> (All [s] (Monad (Parser s)))
(def: functor Functor<Parser>)
(def: (wrap x)
(function (_ input)
(#e.Success [input x])))
(def: (join mma)
(function (_ input)
(case (mma input)
(#e.Error msg)
(#e.Error msg)
(#e.Success [input' ma])
(ma input')))))
## [Parsers]
(def: #export (assert message test)
{#.doc "Fails with the given message if the test is false."}
(All [s] (-> Text Bool (Parser s Any)))
(function (_ input)
(if test
(#e.Success [input []])
(#e.Error message))))
(def: #export (maybe p)
{#.doc "Optionality combinator."}
(All [s a]
(-> (Parser s a) (Parser s (Maybe a))))
(function (_ input)
(case (p input)
(#e.Error _) (#e.Success [input #.None])
(#e.Success [input' x]) (#e.Success [input' (#.Some x)]))))
(def: #export (run input p)
(All [s a]
(-> s (Parser s a) (e.Error [s a])))
(p input))
(def: #export (some p)
{#.doc "0-or-more combinator."}
(All [s a]
(-> (Parser s a) (Parser s (List a))))
(function (_ input)
(case (p input)
(#e.Error _) (#e.Success [input (list)])
(#e.Success [input' x]) (run input'
(do Monad<Parser>
[xs (some p)]
(wrap (list& x xs)))
))))
(def: #export (many p)
{#.doc "1-or-more combinator."}
(All [s a]
(-> (Parser s a) (Parser s (List a))))
(do Monad<Parser>
[x p
xs (some p)]
(wrap (list& x xs))))
(def: #export (seq p1 p2)
{#.doc "Sequencing combinator."}
(All [s a b]
(-> (Parser s a) (Parser s b) (Parser s [a b])))
(do Monad<Parser>
[x1 p1
x2 p2]
(wrap [x1 x2])))
(def: #export (alt p1 p2)
{#.doc "Heterogeneous alternative combinator."}
(All [s a b]
(-> (Parser s a) (Parser s b) (Parser s (| a b))))
(function (_ tokens)
(case (p1 tokens)
(#e.Success [tokens' x1]) (#e.Success [tokens' (+0 x1)])
(#e.Error _) (run tokens
(do Monad<Parser>
[x2 p2]
(wrap (+1 x2))))
)))
(def: #export (either pl pr)
{#.doc "Homogeneous alternative combinator."}
(All [s a]
(-> (Parser s a) (Parser s a) (Parser s a)))
(function (_ tokens)
(case (pl tokens)
(#e.Error _) (pr tokens)
output output
)))
(def: #export (exactly n p)
{#.doc "Parse exactly N times."}
(All [s a] (-> Nat (Parser s a) (Parser s (List a))))
(if (n/> +0 n)
(do Monad<Parser>
[x p
xs (exactly (dec n) p)]
(wrap (#.Cons x xs)))
(:: Monad<Parser> wrap (list))))
(def: #export (at-least n p)
{#.doc "Parse at least N times."}
(All [s a] (-> Nat (Parser s a) (Parser s (List a))))
(do Monad<Parser>
[min (exactly n p)
extra (some p)]
(wrap (list/compose min extra))))
(def: #export (at-most n p)
{#.doc "Parse at most N times."}
(All [s a] (-> Nat (Parser s a) (Parser s (List a))))
(if (n/> +0 n)
(function (_ input)
(case (p input)
(#e.Error msg)
(#e.Success [input (list)])
(#e.Success [input' x])
(run input'
(do Monad<Parser>
[xs (at-most (dec n) p)]
(wrap (#.Cons x xs))))
))
(:: Monad<Parser> wrap (list))))
(def: #export (between from to p)
{#.doc "Parse between N and M times."}
(All [s a] (-> Nat Nat (Parser s a) (Parser s (List a))))
(do Monad<Parser>
[min-xs (exactly from p)
max-xs (at-most (n/- from to) p)]
(wrap (:: list.Monad<List> join (list min-xs max-xs)))))
(def: #export (sep-by sep p)
{#.doc "Parsers instances of 'p' that are separated by instances of 'sep'."}
(All [s a b] (-> (Parser s b) (Parser s a) (Parser s (List a))))
(do Monad<Parser>
[?x (maybe p)]
(case ?x
#.None
(wrap #.Nil)
(#.Some x)
(do @
[xs' (some (seq sep p))]
(wrap (#.Cons x (list/map product.right xs'))))
)))
(def: #export (not p)
(All [s a] (-> (Parser s a) (Parser s Any)))
(function (_ input)
(case (p input)
(#e.Error msg)
(#e.Success [input []])
_
(#e.Error "Expected to fail; yet succeeded."))))
(def: #export (fail message)
(All [s a] (-> Text (Parser s a)))
(function (_ input)
(#e.Error message)))
(def: #export (lift operation)
(All [s a] (-> (Error a) (Parser s a)))
(function (_ input)
(case operation
(#e.Success output)
(#e.Success [input output])
(#e.Error error)
(#e.Error error))))
(def: #export (default value parser)
{#.doc "If the given parser fails, returns the default value."}
(All [s a] (-> a (Parser s a) (Parser s a)))
(function (_ input)
(case (parser input)
(#e.Error error)
(#e.Success [input value])
(#e.Success [input' output])
(#e.Success [input' output]))))
(def: #export remaining
(All [s] (Parser s s))
(function (_ inputs)
(#e.Success [inputs inputs])))
(def: #export (rec parser)
{#.doc "Combinator for recursive parser."}
(All [s a] (-> (-> (Parser s a) (Parser s a)) (Parser s a)))
(function (_ inputs)
(run inputs (parser (rec parser)))))
(def: #export (after param subject)
(All [s _ a] (-> (Parser s _) (Parser s a) (Parser s a)))
(do Monad<Parser>
[_ param]
subject))
(def: #export (before param subject)
(All [s _ a] (-> (Parser s _) (Parser s a) (Parser s a)))
(do Monad<Parser>
[output subject
_ param]
(wrap output)))
(def: #export (filter test parser)
(All [s a] (-> (-> a Bool) (Parser s a) (Parser s a)))
(do Monad<Parser>
[output parser
_ (assert "Constraint failed." (test output))]
(wrap output)))
(def: #export (codec Codec<a,z> parser)
(All [s a z] (-> (codec.Codec a z) (Parser s a) (Parser s z)))
(function (_ input)
(case (parser input)
(#e.Error error)
(#e.Error error)
(#e.Success [input' to-decode])
(case (:: Codec<a,z> decode to-decode)
(#e.Error error)
(#e.Error error)
(#e.Success value)
(#e.Success [input' value])))))
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