diff options
Diffstat (limited to 'src/__OLD_parcom/eof.cr')
| -rw-r--r-- | src/__OLD_parcom/eof.cr | 23 |
1 files changed, 23 insertions, 0 deletions
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 + |
