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/recover.cr | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) create mode 100644 src/__OLD_parcom/recover.cr (limited to 'src/__OLD_parcom/recover.cr') diff --git a/src/__OLD_parcom/recover.cr b/src/__OLD_parcom/recover.cr new file mode 100644 index 0000000..378f8d6 --- /dev/null +++ b/src/__OLD_parcom/recover.cr @@ -0,0 +1,27 @@ +require "./parser.cr" +require "./optional.cr" +require "./map.cr" + +module Parcom + # `Recover` is a `Parser` that tries to parse with another parser, + # but does not fail the parser chain if the wrapped parser fails. + # If the wrapped parser fails, a `Recover` will not modify the input + # stream, and return an arbitrary value of type `V` instead. + class Recover(T, V) < Parser(T, V) + @p : Map(T, V?, V) + + # Accepts the parser to use, and the default value + # to return if the parser fails. + def initialize(p : Parser(T, V), default : V) + @p = Optional.new(p).map { |x| x.nil? ? default : x } + end + + # Tries to parse with the given parser, succeeds with the + # default value instead of failing. This parser does not + # consume input if the wrapped parser fails. + def parse(tokens : Tokens(T)) : Result(T, V) + @p.parse(tokens) + end + end +end + -- cgit v1.2.1