From: Issac Trotts <ITrotts@...>
Date: 2001-12-11T12:24:55+09:00
Subject: [ruby-talk:28170] c++2rb

Here's a little program to partially automate conversion from C++ to Ruby.  
If you make any improvements, please let me know.

A few things surprised me about the script:

1. When I tried to move the body of the while loop into a separate function
taking
   no args, the script suddenly stopped working.  The expressions only use
$_ so I don't
   see what the trouble is.  Here's the error message:

	c2rb:19:in `gsub!': $_ value need to be String (nil given)
(TypeError)

   Isn't $_ supposed to be global?

2. See the line that says "WHY DOESN'T THIS WORK?"

3. The failed attempt at making a regular expression for constructors (see
below).
   I want to match a pattern that looks like FOO::FOO()

One more question before I go: 
	What are the Ruby equivalents of 'using namespace foo;'
	and 'using foo::foomember;'?



======= %< ========

#!/usr/bin/env ruby
#
# c++2rb : partial conversion from C and C++ to Ruby
#
# Copyright (c) 2001 Issac Trotts <itrotts at idolminds dot com>
#
# Under the Ruby license 
#
# TODO
# - template functions
# - template classes

type_re = '(void|char|short|int|long|float|double)'
map_re = '\bmap\s*<.*>'
list_re = '\blist\s*<.*>'
vector_re = '\bvector\s*<.*>'
token_re = '[a-zA-Z_][a-zA-Z0-9_]*'

while gets
    gsub!(/;/, '')
    gsub!(/#include\s+\<([^>.]+)(.h)?>/, 'require \'\1\'')
    gsub!(/const\s*/, '')
    gsub!(/unsigned\s*/, '')
    eval('gsub!(/#{list_re}\s*(#{token_re})/, \'\1 = []\')')
    eval('gsub!(/#{vector_re}\s*(#{token_re})/, \'\1 = []\')')
    eval('gsub!(/#{map_re}\s*(#{token_re})/, \'\1 = {}\')')
    gsub!(/push_back/, 'push')
    gsub!(/std::/, '')
    gsub!(/cout\s*\<\</, 'puts ')
    gsub!(/\<\</, '+')
    gsub!(/this/, 'self')
    gsub!(/endl/, '"\n"')
    gsub!(/(public|protected|private)\:/, '\1')
    # comments
    gsub!(/\/\//, '#')                             
    gsub!(/\{/, '')
    gsub!(/(\s*)}/, '\1end')
    sub!(/(\S)+(\s)*}/, '\1\2; end') # WHY DOESN'T THIS WORK?
    gsub!(/case/, 'when')
    gsub!(/switch/, 'case')
    gsub!(/default/, 'else')
    gsub!(/struct/, 'class')
    gsub!(/virtual\s*/, '')
    gsub!(/if\s*\(([^)]+)\)/, 'if \1')
    #gsub!(/if\(([^)]+)\)\s*(\S*)$/, 'if \1; \2')
    # inheritance
    gsub!(/:\s+(public|private|protected)/, '<')    
    gsub!(/\-\>/, '.')
    # global functions with no args
    eval("sub!(/#{type_re}\\s+(#{token_re})\\s*\\(\\s*\\)/, "+
        '\'def \2\')')
    # global functions with args
    eval("sub!(/#{type_re}\\s+(#{token_re})\\s*(\\(.*\\))\s*{?/, "+
         '\'def \2\3\')')
    # constructors 
    #eval("gsub!(/#{(token_re)::\$1(.*)/, 'def initialize\2')")
    # member functions with no args
    eval("sub!(/#{type_re}\\s+(#{token_re})::(#{token_re})\\s*\\(\\s*\\)/,
"+
         '\'class \2; def \3 # FIXME: put another end at the end\')') 
    # member functions with args
    eval("sub!(/#{type_re}\\s+(#{token_re})::(#{token_re})\\s*\\((.*)\\)/,
"+
         '\'class \2; def \3 (\4) # FIXME: put another end at the end\')') 
    # member function invocations with no args

    # member function invocations with args

    # for-loops...

    # using std::cout etc

    # using namespace X

    # namespaces
    gsub!(/namespace/, 'module')

    print 
end