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require "./parser.cr"
require "./eof.cr"
require "./map.cr"
module Parcom
# `Phrase` is a `Parser` that tries to parse with another parser,
# but will fail if any of the input has not been consumed.
#
# Example:
# ```
# letter_a = Token.new('a')
# tokens = Tokens.from_string("aaa")
# one_a = Phrase(Char, Char).new(letter_a)
# result = one_a.parse(tokens) # This fails
# ```
class Phrase(T, V) < Parser(T, V)
@p : Map(T, {V, Nil}, V)
# Accepts the parser to parse with.
def initialize(p : Parser(T, V))
@p = (p + EOF(T).new).map &.first
end
# Tries to parse with the given parser, fails if there
# is any un-parsed input remaining.
def parse(tokens : Tokens(T)) : Result(T, V)
@p.parse(tokens)
rescue ex : ParserFail
raise ParserFail.new("Phrase: #{ex.message}")
end
end
end
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