CaffeineEight

Come to C8 because you want an elegant, declarative API that makes parsing as easy as humanly possible. Stay for super powers like detailed parsing errors, predictable PEG-based parsing and runtime parser extendability.

Unlike other parsing libraries, CaffeineEight is not a parser-generator. There is no build step. Just extend a class, add some rules and you are ready to parse. With CaffeineEight you can create and, more importantly, extend your parsers at runtime.

Motivating Example

A complete JSON parser in less than 30 lines of code.

# CaffeineScript
class JsonParser extends &CaffeineEight.Parser
  @rule
    root: :array :object
    array:
      "'[' _? ']'"
      "'[' _? value commaValue* _? ']'"
    object:
      "'{' _? '}'"
      "'{' _? pair commaPair* _? '}'"
    commaValue: "_? ',' _? value"
    commaPair:  "_? ',' _? pair"
    pair:       "string _? ':' _? value"
    value: :object :array :number :string :true :false :null
    string: /"(?:[^"\\]|\\(?:["\\\/bfnrt]|u[0-9a-fA-F]{4}))*"/
    number: /-?(?:0|[1-9]\d*)(?:\.\d+)?(?:[eE][+-]?\d+)?/
    true:   /true/
    false:  /false/
    null:   /null/
    _:      /\ +/
.repl()

Goals

• Define PEG parsers 100% in JavaScript
• Runtime-extensible parsers
• Reasonably fast
• No globals - each parser instance parses in its own space

Features

• Full parsing expression grammar support with memoizing
• Full JavaScript regular expressions support for terminals
• Simple, convention-over-configuration parse-tree class structure
• Human-readable parse-tree dumps
• Detailed information about parsing failures
• Custom sub-parser hooks
  • Which enable indention-based block parsing for languages like Python, CoffeeScript, or my own CaffeineScript

Learn More

• Wiki Home

Rename History

• CaffeineEight was formally called BabelBridgeJs
• CaffeineEight was inspired by my earlier Babel Bridge Ruby Gem, the JavaScript version turned out to be even more awesome!