Ripper

Class

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

Requirements

  • ruby 1.9 (support CVS HEAD only)

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

License

Ruby License.

Constants

PARSER_EVENTS

This array contains name of parser events.

SCANNER_EVENTS

This array contains name of scanner events.

EVENTS

This array contains name of all ripper events.

Class Methods

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

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)
::

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)
::
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)
::
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)
::
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)
::

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"]
Instance Methods

compile_error(msg)
#

This method is called when the parser found syntax error.

warn(fmt, *args)
#

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

warning(fmt, *args)
#

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