class Ripper - Documentation for Ruby 4.0
Description: class Ripper: Ripper is a Ruby script parser. You can get information from the parser with event-based style.
Keywords: ruby,class,Ripper

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# class Ripper

`Ripper` is a Ruby script parser.

You can get information from the parser with event-based style. Information such as abstract syntax trees or simple lexical analysis of the Ruby program.

## Usage

`Ripper` provides an easy interface for parsing your program into a symbolic expression tree (or S-expression).

Understanding the output of the parser may come as a challenge, it’s recommended you use `PP` to format the output for legibility.

    require 'ripper'
    require 'pp'

    pp Ripper.sexp('def hello(world) "Hello, #{world}!"; end')
      #=> [:program,
           [[:def,
             [:@ident, "hello", [1, 4]],
             [:paren,
              [:params, [[:@ident, "world", [1, 10]]], nil, nil, nil, nil, nil, nil]],
             [:bodystmt,
              [[:string_literal,
                [:string_content,
                 [:@tstring_content, "Hello, ", [1, 18]],
                 [:string_embexpr, [[:var_ref, [:@ident, "world", [1, 27]]]]],
                 [:@tstring_content, "!", [1, 33]]]]],
              nil,
              nil,
              nil]]]]

You can see in the example above, the expression starts with `:program`.

From here, a method definition at `:def`, followed by the method’s identifier `:@ident`. After the method’s identifier comes the parentheses `:paren` and the method parameters under `:params`.

Next is the method body, starting at `:bodystmt` (`stmt` meaning statement), which contains the full definition of the method.

In our case, we’re simply returning a `String`, so next we have the `:string_literal` expression.

Within our `:string_literal` you’ll notice two `@tstring_content`, this is the literal part for `Hello,` and `!`. Between the two `@tstring_content` statements is a `:string_embexpr`, where embexpr is an embedded expression. Our expression consists of a local variable, or `var_ref`, with the identifier (`@ident`) of `world`.

## Resources

- Ruby Inside

## Requirements

- ruby 1.9 (support CVS HEAD only)

- bison 1.28 or later (Other yaccs do not work)

## License

Ruby License.

- Minero Aoki

- aamine@loveruby.net

- i.loveruby.net

### Constants

EVENTS

  This array contains name of all ripper events.

PARSER_EVENTS

  This array contains name of parser events.

SCANNER_EVENTS

  This array contains name of scanner events.

### Public Class Methods

lex (src, filename = '-', lineno = 1, **kw)
Source

    # File ext/ripper/lib/ripper/lexer.rb, line 51
    def Ripper.lex(src, filename = '-', lineno = 1, **kw)
      Lexer.new(src, filename, lineno).lex(**kw)
    end

Tokenizes the Ruby program and returns an array of an array, which is formatted like `[[lineno, column], type, token, state]`. The `filename` argument is mostly ignored. By default, this method does not handle syntax errors in `src`, use the `raise_errors` keyword to raise a `SyntaxError` for an error in `src`.

    require 'ripper'
    require 'pp'

    pp Ripper.lex("def m(a) nil end")
    #=> [[[1,  0], :on_kw,     "def", FNAME    ],
         [[1,  3], :on_sp,     " ",   FNAME    ],
         [[1,  4], :on_ident,  "m",   ENDFN    ],
         [[1,  5], :on_lparen, "(",   BEG|LABEL],
         [[1,  6], :on_ident,  "a",   ARG      ],
         [[1,  7], :on_rparen, ")",   ENDFN    ],
         [[1,  8], :on_sp,     " ",   BEG      ],
         [[1,  9], :on_kw,     "nil", END      ],
         [[1, 12], :on_sp,     " ",   END      ],
         [[1, 13], :on_kw,     "end", END      ]]

parse (src, filename = '(ripper)', lineno = 1)
Source

    # File ext/ripper/lib/ripper/core.rb, line 18
    def Ripper.parse(src, filename = '(ripper)', lineno = 1)
      new(src, filename, lineno).parse
    end

Parses the given Ruby program read from `src`. `src` must be a `String` or an `IO` or a object with a `gets` method.

sexp (src, filename = '-', lineno = 1, raise_errors: false)
Source

    # File ext/ripper/lib/ripper/sexp.rb, line 35
    def Ripper.sexp(src, filename = '-', lineno = 1, raise_errors: false)
      builder = SexpBuilderPP.new(src, filename, lineno)
      sexp = builder.parse
      if builder.error?
        if raise_errors
          raise SyntaxError, builder.error
        end
      else
        sexp
      end
    end

EXPERIMENTAL

  Parses `src` and create S-exp tree. Returns more readable tree rather than `Ripper.sexp_raw`. This method is mainly for developer use. The `filename` argument is mostly ignored. By default, this method does not handle syntax errors in `src`, returning `nil` in such cases. Use the `raise_errors` keyword to raise a `SyntaxError` for an error in `src`.

      require 'ripper'
      require 'pp'

      pp Ripper.sexp("def m(a) nil end")
        #=> [:program,
             [[:def,
              [:@ident, "m", [1, 4]],
              [:paren, [:params, [[:@ident, "a", [1, 6]]], nil, nil, nil, nil, nil, nil]],
              [:bodystmt, [[:var_ref, [:@kw, "nil", [1, 9]]]], nil, nil, nil]]]]

sexp_raw (src, filename = '-', lineno = 1, raise_errors: false)
Source

    # File ext/ripper/lib/ripper/sexp.rb, line 71
    def Ripper.sexp_raw(src, filename = '-', lineno = 1, raise_errors: false)
      builder = SexpBuilder.new(src, filename, lineno)
      sexp = builder.parse
      if builder.error?
        if raise_errors
          raise SyntaxError, builder.error
        end
      else
        sexp
      end
    end

EXPERIMENTAL

  Parses `src` and create S-exp tree. This method is mainly for developer use. The `filename` argument is mostly ignored. By default, this method does not handle syntax errors in `src`, returning `nil` in such cases. Use the `raise_errors` keyword to raise a `SyntaxError` for an error in `src`.

      require 'ripper'
      require 'pp'

      pp Ripper.sexp_raw("def m(a) nil end")
        #=> [:program,
             [:stmts_add,
              [:stmts_new],
              [:def,
               [:@ident, "m", [1, 4]],
               [:paren, [:params, [[:@ident, "a", [1, 6]]], nil, nil, nil]],
               [:bodystmt,
                [:stmts_add, [:stmts_new], [:var_ref, [:@kw, "nil", [1, 9]]]],
                nil,
                nil,
                nil]]]]

slice (src, pattern, n = 0)
Source

    # File ext/ripper/lib/ripper/lexer.rb, line 277
    def Ripper.slice(src, pattern, n = 0)
      if m = token_match(src, pattern)
      then m.string(n)
      else nil
      end
    end

EXPERIMENTAL

  Parses `src` and return a string which was matched to `pattern`. `pattern` should be described as `Regexp`.

      require 'ripper'

      p Ripper.slice('def m(a) nil end', 'ident')                   #=> "m"
      p Ripper.slice('def m(a) nil end', '[ident lparen rparen]+')  #=> "m(a)"
      p Ripper.slice("<<EOS\nstring\nEOS",
                     'heredoc_beg nl $(tstring_content*) heredoc_end', 1)
          #=> "string\n"

tokenize (src, filename = '-', lineno = 1, **kw)
Source

    # File ext/ripper/lib/ripper/lexer.rb, line 25
    def Ripper.tokenize(src, filename = '-', lineno = 1, **kw)
      Lexer.new(src, filename, lineno).tokenize(**kw)
    end

Tokenizes the Ruby program and returns an array of strings. The `filename` and `lineno` arguments are mostly ignored, since the return value is just the tokenized input. By default, this method does not handle syntax errors in `src`, use the `raise_errors` keyword to raise a `SyntaxError` for an error in `src`.

    p Ripper.tokenize("def m(a) nil end")
       # => ["def", " ", "m", "(", "a", ")", " ", "nil", " ", "end"]

### Private Instance Methods

compile_error (msg)
Source

    # File ext/ripper/lib/ripper/core.rb, line 63
    def compile_error(msg)
    end

This method is called when the parser found syntax error.

warn (fmt, *args)
Source

    # File ext/ripper/lib/ripper/core.rb, line 54
    def warn(fmt, *args)
    end

This method is called when weak warning is produced by the parser. `fmt` and `args` is printf style.

warning (fmt, *args)
Source

    # File ext/ripper/lib/ripper/core.rb, line 59
    def warning(fmt, *args)
    end

This method is called when strong warning is produced by the parser. `fmt` and `args` is printf style.