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/eof.cr | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) create mode 100644 src/__OLD_parcom/eof.cr (limited to 'src/__OLD_parcom/eof.cr') diff --git a/src/__OLD_parcom/eof.cr b/src/__OLD_parcom/eof.cr new file mode 100644 index 0000000..650da56 --- /dev/null +++ b/src/__OLD_parcom/eof.cr @@ -0,0 +1,23 @@ +require "./parser.cr" + +module Parcom + # `EOF` is a `Parser` succeeds if the input stream is empty. + # + # This parser retuns `nil` when successful because there is no + # other meaningful value to return. + # + # This parser is also one of the few cases where it is ideal to not + # modify or take from the input stream, as it should be empty anyway. + class EOF(T) < Parser(T, Nil) + # Succeeds is the input stream is empty and returns `nil`. + # Raises a `ParserFail` exception when the input is not empty. + def parse(tokens : Tokens(T)) : Result(T, Nil) + if tokens.empty? + Result.new(tokens, nil) + else + raise ParserFail.new("Eof: input was not empty") + end + end + end +end + -- cgit v1.2.1