From b274828831fec26cd8b3089ffef14cb96ce2de2f Mon Sep 17 00:00:00 2001 From: Matthew Hall Date: Thu, 16 Mar 2023 20:36:03 +1300 Subject: Second rewrite attempt, this one should work, monkaS --- src/__OLD_parcom/left.cr | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) create mode 100644 src/__OLD_parcom/left.cr (limited to 'src/__OLD_parcom/left.cr') diff --git a/src/__OLD_parcom/left.cr b/src/__OLD_parcom/left.cr new file mode 100644 index 0000000..201f497 --- /dev/null +++ b/src/__OLD_parcom/left.cr @@ -0,0 +1,26 @@ +require "./parser.cr" +require "./map.cr" + +module Parcom + # `Left` 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 first parser. + class Left(T, V, U) < Parser(T, V) + @p : Map(T, {V, U}, V) + + # Accepts the two parsers to use, in order. + def initialize(p1 : Parser(T, V), p2 : Parser(T, U)) + @p = (p1 + p2).map(&.first) + end + + # Tries to parse with the two given parsers, and returns the + # result of the first parser if they both succeed. + def parse(tokens : Tokens(T)) : Result(T, V) + @p.parse(tokens) + rescue ex : ParserFail + raise ParserFail.new("Left: #{ex.message}") + end + end +end + -- cgit v1.2.1