diff options
Diffstat (limited to 'src/__OLD_parcom/plus.cr')
| -rw-r--r-- | src/__OLD_parcom/plus.cr | 54 |
1 files changed, 0 insertions, 54 deletions
diff --git a/src/__OLD_parcom/plus.cr b/src/__OLD_parcom/plus.cr deleted file mode 100644 index 53c9b4f..0000000 --- a/src/__OLD_parcom/plus.cr +++ /dev/null @@ -1,54 +0,0 @@ -require "./parser.cr" - -module Parcom - # `Plus` is a parser that tries to parse with two different - # parsers in succession and fails if either of the two parsers fails. - # The return type of this parser is `{V, U}`, where `V` is the return - # type of the first parser and `U` is the return type of the second. - # - # Example: - # ``` - # parse1 = Token.new('1') - # parse2 = Token.new('2') - # tokens = Tokens.from_string("12") - # result = (parse1 + parse2).parse(tokens) # succeeds - # result = (parse2 + parse1).parse(tokens) # fails, wrong order - # ``` - # - # `Plus` parsers can be chained together, but the resulting return type - # can become unweildly with too many combined parsers: - # ``` - # letter_a = Token.new('a') - # a5 = letter_a + letter_a + letter_a + letter_a + letter_a - # tokens = Tokens.from_string("aaaaa") - # a5.parse(tokens) # succeeds - # # `a5` has a return type of { { { {Char, Char}, Char}, Char}, Char} - # ``` - # - # If you need to parse more than two things in this manner, - # consider using `Many`, `Some`, `Sequence`, or `TokenSeq` instead. - class Plus(T, V, U) < Parser(T, {V, U}) - # Accepts the two parsers to use, in order. - def initialize(@p1 : Parser(T, V), @p2 : Parser(T, U)) - end - - # Tries to parse with the two given parsers, and returns - # their results in a tuple if the both succeed. - def parse(tokens : Tokens(T)) : Result(T, {V, U}) - begin - r1 = @p1.parse(tokens) - rescue ex : ParserFail - raise ParserFail.new("Plus (left): #{ex.message}") - end - - begin - r2 = @p2.parse(r1.tokens) - rescue ex : ParserFail - raise ParserFail.new("Plus (right): #{ex.message}") - end - - Result.new(r2.tokens, {r1.value, r2.value}) - end - end -end - |
