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|
module Parcom
VERSION = "0.1.0"
class ParserException < Exception
end
struct TokenStream(T)
getter tokens
def self.from_string(s : String) : TokenStream(Char)
TokenStream.new(s.chars)
end
def initialize(ts : Iterable(T))
if ts.responds_to?(:to_a)
@tokens = ts.to_a
else
@tokens = [] of T
ts.each { |t| @tokens << t }
end
end
def [](index : Int) : T
@tokens[index]
end
def [](start : Int, count : Int) : TokenStream(T)
TokenStream.new(@tokens[start, count])
end
def [](range : Range) : TokenStream(T)
TokenStream.new(@tokens[range])
end
def []?(*args)
self.[](*args)
rescue IndexError
nil
end
def empty? : Bool
@tokens.empty?
end
end
struct Result(T, V)
getter tokens, value
def initialize(@tokens : TokenStream(T), @value : V)
end
end
abstract class Parser(T, V)
abstract def parse(tokens : TokenStream(T)) : Result(T, V)
def parse?(tokens : TokenStream(T)) : Result(T, V)?
self.parse(tokens)
rescue
return nil
end
def |(other : Parser(T, V)) : Alt(T, V)
Alt.new(self, other)
end
def +(other : Parser(T, U)) : Plus(T, V, U) forall U
Plus.new(self, other)
end
def assert(f : V -> Bool)
Assert.new(self, f)
end
def map(f : V -> U) : Map(T, V, U) forall U
Map.new(self, f)
end
def recover(default : T)
Recover.new(self, default)
end
end
class Flunk(T, V) < Parser(T, V)
def parse(tokens) : Result(T, V)
raise ParserException.new("Flunk: parsing failed")
end
end
class AnyToken(T) < Parser(T, T)
def parse(tokens : TokenStream(T)) : Result(T, T)
if tokens.empty?
raise ParserException.new("AnyToken: input was empty")
else
Result.new(tokens[1..], tokens[0])
end
end
end
class Eof(T) < Parser(T, Nil)
def parse(tokens : TokenStream(T)) : Result(T, Nil)
if tokens.empty?
Result.new(tokens, nil)
else
raise ParserException.new("Eof: input was not empty")
end
end
end
class Peek(T, V) < Parser(T, V)
def initialize(@p : Parser(T, V))
end
def parse(tokens : TokenStream(T)) : Result(T, V)
result = @p.parse(tokens)
Result.new(tokens, result.value)
end
end
class Assert(T, V) < Parser(T, V)
def initialize(@p : Parser(T, V), @f : V -> Bool)
end
def parse(tokens : TokenStream(T)) : Result(T, V)
result = @p.parse(tokens)
unless @f.call(result.value)
raise ParserException.new("Assert: predicate failed")
end
result
end
end
class Satisfy(T) < Parser(T, T)
def initialize(@f : T -> Bool)
end
def parse(tokens : TokenStream(T)) : Result(T, T)
AnyToken(T).new.assert(@f).parse(tokens)
end
end
class Token(T) < Parser(T, T)
def initialize(@expected : T)
end
def parse(tokens : TokenStream(T)) : Result(T, T)
Satisfy(T).new(->(x : T) { x == @expected }).parse(tokens)
end
end
class Alt(T, V) < Parser(T, V)
def initialize(@p1 : Parser(T, V), @p2 : Parser(T, V))
end
def parse(tokens : TokenStream(T)) : Result(T, V)
@p1.parse(tokens)
rescue ParserException
@p2.parse(tokens)
end
end
class Map(T, V, U) < Parser(T, U)
def initialize(@p : Parser(T, V), @f : V -> U)
end
def parse(tokens : TokenStream(T)) : Result(T, U)
result = @p.parse(tokens)
Result.new(result.tokens, @f.call(result.value))
end
end
class Phrase(T, V)
def initialize(@p : Parser(T, V))
end
def parse(tokens : TokenStream(T)) : Result(T, V)
r = @p.parse(tokens)
unless r.tokens.empty?
raise ParserException.new("Phrase: some of the input was not parsed")
end
r
end
end
class Plus(T, V, U) < Parser(T, {V, U})
def initialize(@p1 : Parser(T, V), @p2 : Parser(T, U))
end
def parse(tokens : TokenStream(T)) : Result(T, {V, U})
r1 = @p1.parse(tokens)
r2 = @p2.parse(r1.tokens)
Result.new(r2.tokens, {r1.value, r2.value})
end
end
class Recover(T, V) < Parser(T, V)
def initialize(@p : Parser(T, V), @default : V)
end
def parse(tokens : TokenStream(T)) : Result(T, V)
@p.parse?(tokens) || Result.new(tokens, @default)
end
end
# TODO: find a way to make this use Recover on the back end
class Optional(T, V) < Parser(T, V?)
def initialize(@p : Parser(T, V))
end
def parse(tokens : TokenStream(T)) : Result(T, V?)
r = @p.parse?(tokens)
new_tokens = r.nil? ? tokens : r.tokens
new_value = r.nil? ? nil : r.value
Result.new(new_tokens, new_value)
end
end
class Tokens
end
class Many
end
class Some
end
class Exactly
end
class AtLeast
end
class AtMost
end
class Between
end
class StopAt
end
class StopAfter
end
class StopIf
end
class FirstOf
end
class SepBy
end
end
|
