blob: a0489b17c532ba2d270d96a73650d0d0b24a6457 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
|
require "./parser.cr"
require "./map.cr"
module Parcom
# `Right` is a `Parser` that tries to parse with two different
# parsers in succession and fails if either of the two parsers fails.
# This parser behaves the same as `Plus`, but only returns the result
# of the second parser.
class Right(T, V, U) < Parser(T, U)
@p : Map(T, {V, U}, U)
# Accepts the two parsers to use, in order.
def initialize(p1 : Parser(T, V), p2 : Parser(T, U))
@p = (p1 + p2).map(&.last)
end
# Tries to parse with the two given parsers, and returns the
# result of the second parser if they both succeed.
def parse(tokens : Tokens(T)) : Result(T, U)
@p.parse(tokens)
rescue ex : ParserFail
raise ParserFail.new("Left: #{ex.message}")
end
end
end
|
