blob: dedd41d2ede112573e21525837d56c3d480d712a (
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
27
28
|
require "./parser.cr"
module Parcom
# `Alt` is a `Parser` that accepts two other parsers and tries
# to parse with one of them.
# If the first (left) parser succeeds, its result is returned.
# If the first parser fails, it will try the second (right) parser.
class Alt(T, V) < Parser(T, V)
# Accepts the two parsers to try to parse with.
def initialize(@p1 : Parser(T, V), @p2 : Parser(T, V))
end
# Tries to parse using both parsers.
#
# It will initially try to parse with the first parser.
# If it fails, it will try to parse with the second parser.
def parse(tokens : Tokens(T)) : Result(T, V)
@p1.parse(tokens)
rescue ex1 : ParserFail
begin
@p2.parse(tokens)
rescue ex2 : ParserFail
raise ParserFail.new("Alt (#{ex1.message}), (#{ex2.message})")
end
end
end
end
|
