From: Shashank Date <ADATE@...>
Date: 2002-09-10T15:53:24+09:00
Subject: Rockit problem

Ruby + Rockit gurus,

I am using ruby 1.7.2 (2002-07-02) [i386-mswin32]

Downloaded and installed Rockit (rockit-0-3-8.tar.gz) and Memoize
(memoize-0-1-2.tar.gz).

Ran the example Expression Grammar given at http://rockit.sourceforge.net/
(see code below)

Got the following errors:

         C:\tst_rockit.rb:35: warning: parenthesize argument(s) for future
version
         C:/ruby/lib/ruby/site_ruby/resultcache.rb:5: warning: already
initialized constant BoundedLruCache
         C:/ruby/lib/ruby/site_ruby/rockit/rockit.rb:24:in
`generate_parser': undefined local variable or method
            `rockit_grammars_parser' for  Parse:Module (NameError)  from
C:\tst_rockit.rb:3

What did I miss?

TIA,

-- Shanko

#-------------------- tst_rockit.rb ---------------------------------
# Example of using the rockit lib in Ruby code
require 'rockit/rockit'

parser = Parse.generate_parser <<-'END_OF_GRAMMAR'
 Grammar ExampleGrammar
  Tokens
    Blank      = /\s+/             [:Skip]
    Number     = /\d+/
  Productions
    Expr       -> Number           [^]
               |  Expr '+' Expr    [Plus: left,_,right]
               |  Expr '-' Expr    [Minus: left,_,right]
               |  Expr '*' Expr    [Mul: left,_,right]
               |  Expr '/' Expr    [Div: left,_,right]
               |  '(' Expr ')'     [^: _,expr,_]
  Priorities
    left(Plus), left(Minus), left(Mul), left(Div)
    Div = Mul > Plus = Minus
END_OF_GRAMMAR

def calc_eval(ast)
  case ast.name
  when "Plus"
    calc_eval(ast.left) + calc_eval(ast.right)
  when "Minus"
    calc_eval(ast.left) - calc_eval(ast.right)
  when "Mul"
    calc_eval(ast.left) * calc_eval(ast.right)
  when "Div"
    calc_eval(ast.left) / calc_eval(ast.right)
  when "Number"
    ast.lexeme.to_i
  end
end

calc_eval(parser.parse '(4*((2+6)-3))/2')    # => 10
#-------------------------------------------------------