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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 assert(&block : V -> Bool)
Assert.new(self, &block)
end
def map(&block : V -> U) : Map(T, V, U) forall U
Map.new(self, &block)
end
def map(f : V -> U) : Map(T, V, U) forall U
Map.new(self, &f)
end
def recover(default : V) : Recover(T, V)
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), &block : V -> Bool)
@f = block
end
def parse(tokens : TokenStream(T)) : Result(T, V)
result = @p.parse(tokens)
unless @f.call(result.value)
raise ParserException.new("Assert: predicate failed for <#{result.value}>")
end
result
end
end
class Satisfy(T) < Assert(T, T)
def initialize(&block : T -> Bool)
super(AnyToken(T).new, &block)
end
end
class Token(T) < Parser(T, T)
def initialize(@expected : T)
@p = Satisfy(T).new { |x| x == @expected }
end
def parse(tokens : TokenStream(T)) : Result(T, T)
@p.parse(tokens)
rescue ex : ParserException
raise ParserException.new("Token <#{@expected}>: #{ex.message}")
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), &block : V -> U)
@f = block
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)
@p : Map(T, {V, Nil}, V)
def initialize(p : Parser(T, V))
@p = (p + Eof(T).new).map &.first
end
def parse(tokens : TokenStream(T)) : Result(T, V)
@p.parse(tokens)
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)
@p : Map(T, V?, V)
def initialize(p : Parser(T, V), default : V)
@p = Optional.new(p).map { |x| x.nil? ? default : x }
end
def parse(tokens : TokenStream(T)) : Result(T, V)
@p.parse(tokens)
end
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 Sequence(T, V) < Parser(T, Array(V))
def initialize(@ps : Iterable(Parser(T, V)))
end
# TODO: this can probably be optimised more for Arrays
# TODO: might be better to use #zip
def parse(tokens : TokenStream(T)) : Result(T, Array(V))
parsed = [] of V
@ps.each do |p|
r = p.parse(tokens)
parsed << r.value
tokens = r.tokens
end
Result.new(tokens, parsed)
end
end
class Tokens(T) < Parser(T, Array(T))
@p : Sequence(T, T)
def initialize(expected : Iterable(T))
ps = [] of Parser(T, T)
expected.each { |t| ps << Token.new(t) }
@p = Sequence.new(ps)
end
def parse(tokens : TokenStream(T)) : Result(T, Array(T))
@p.parse(tokens)
end
end
class Many(T, V) < Parser(T, Array(V))
def initialize(@p : Parser(T, V))
end
def parse(tokens : TokenStream(T)) : Result(T, Array(V))
parsed = [] of V
loop do
result = @p.parse?(tokens)
if result.nil?
break
else
parsed << result.value
tokens = result.tokens
end
end
Result.new(tokens, parsed)
end
end
class Some(T, V) < Parser(T, Array(V))
@p : Assert(T, Array(V))
def initialize(p : Parser(T, V))
@p = Many.new(p).assert { |arr| !arr.empty? }
end
def parse(tokens : TokenStream(T)) : Result(T, Array(V))
@p.parse(tokens)
end
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
|
