parsec-free

Parsec API encoded as a deeply-embedded DSL, for debugging and analysis

Monthly Downloads: 27

Programming language: Haskell

License: MIT License

Tags: Text     Parsing     Parsec    

README

Welcome to parsec-free, a deep-embedding of the Parsec API, to allow for comprehensive debugging and analysis of Parsec-style parsers.

To use it, simply replace your dependency on parsec with parsec-free. None of your code should need to change. Then, use parseTestLog rather than parseTest, and you should see output like the following:

label "object name"
  reserved "object"
  identifier => "aascllwl"
parserPlus
- (reserved "identity")
+ return
parserPlus
+ reserved "state"
  label "var decls"
    sepEndBy1
    + label "var decl"
        label "type"
          choice
          - (reserved "int")
          - (reserved "pointer")
          + label "type name"
              identifier => "bool"
        commaSep1
        + sepBy1
          + label "variable name"
              identifier => "nlenshiy"
          - (string ",")
    + symbol ";"
    - (label "var decl")
        (label "type")
          (choice)
          - (reserved "int")
          - (reserved "pointer")
          - (label "type name")
              (identifier)
parserPlus
+ reserved "events"
  sepEndBy1
  + label "event defs"
      label "event definition kind"
        choice
        - (reserved "internal")
        + reserved "imported"
      label "error keyword"
        parserPlus
        + reserved "error"
      commaSep1
      + sepBy1
        + label "event name"
            identifier => "swehegge"
          label "event params"
            parens
              between
              + string "("
              + commaSep
                + sepBy
                  - (label "type")
                      (choice)
                      - (reserved "int")
                      - (reserved "pointer")
                      - (label "type name")
                          (identifier)
              + string ")"
          label "event definiton"
            parserPlus
            + reservedOp "="
              label "expr"
                label "buildExpressionParser"
        - (string ",")
  + symbol ";"
  - (label "event defs")
      (label "event definition kind")
        (choice)
        - (reserved "internal")
        - (reserved "imported")
        - (reserved "exported")
...

Things to note in this output:

• Terms in parentheses represent a failed attempt to parse along that branch.
• If a term ends with ..., it means the parser did not complete before an exception occurred. This makes it easy to follow the chain of parsers "up to the error", although there is no such output above.
• Parsers with potentially more than 1 children use bullets to show those children. These bullets have the following meaning: - if the parser failed, + if it succeeded, ? if it was pending completion before an exception occurred.
• A failed parser followed by * also consumed input. These will prevent the second branch of <|> from being attempted, and may indicate the need for try.

Also, parserPlus is the name for <|>, while label is <?>.