Ruby regex for removing C/Java-style /* ... */ comments

Question posted by: beatTheDevil (Newbie) on July 31st, 2007 06:52 PM

Hey guys,

As the title says I'm trying to make a regular expression (regex/regexp) for use in removing the comments from code. In this case, this particular regex is meant to match /* ... */ comments.

I'm using Ruby v.1.8.6

Here's my regex:

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multiline_comments = /\/\*(.*?)\*\//

When I try

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myStr.gsub(multiline_comments, "")

I see no effect. The string has big fat comments in it too. I tried using this regex in irb with a couple test strings, and it works perfectly. This leads me to think I don't understand some subtlety of file io, so here's all my code (cop-out, I know). I'm trying to write a very simple JavaScript compacter, but I want to preserve readability so I'm only getting rid of unnecessary newlines, spaces in between tokens, and comments. I DON'T want the whole file on one line like some compactors do it. Anyway, here goes:

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# Non-destructive JavaScript Packer

# =================================

#

# Reduces overall script filesize by removing comments

# and unecessary whitespace. Does not affect variable naming,

# indentation, or line-by-line formatting in order to maximize

# readability.
 
def pack_line(file_line)
 
    return '' unless file_line
 
    #puts "The next line: " + file_line
 
    #kill one-line (//...) comments

    line_comments = /(\S*)\s*\/\/.*/

    intermed = file_line.gsub(line_comments, '\1')

    intermed += "\n" if intermed[intermed.length - 1] != "\n"
 
    #puts "\tAfter one-liner removal: " + intermed
 
    #kill unnecessary whitespace

    extra_whitespace = /([^(var|function|return|\s*)])[ \t]+(.*?)/

    intermed = intermed.gsub(extra_whitespace, '\1\2')
 
    #puts "\tAfter extra whitespace removal: " + intermed
 
    intermed

end
 
#performs the packing operation, returns a single string

#representing the packed document

def pack(file)

    lines = Array.new
 
    file.each_line do |line|

        lines.push pack_line(line)

    end
 
    intermed = lines.join
 
    #puts "\tBefore multi-liner removal: " + intermed
 
    #kill multi-line (/* ... */) comments

    multiline_comments = /\/\*(.*?)\*\//

    intermed = intermed.gsub(multiline_comments, '')
 
    #puts "\tAfter multi-liner removal: " + intermed
 
    #kill extra new lines

    extra_newlines = /(\r?\n){2,}/

    intermed = intermed.gsub(extra_newlines, "\n")
 
    #puts "\tFinally: " + intermed + "\n"
 
    intermed

end
 
#open file for reading and pass it to pack()

def init(in_file, out_file)

    file = File.new(in_file, "r")
 
    newDoc = pack(file)
 
    file.close
 
    if out_file then

        file = File.new(out_file, "w")
 
        file.puts(newDoc)
 
        file.close

    else

        puts newDoc

    end

end
 
#start the script with the command-line arg file name

puts init(ARGV[0], ARGV[1])

Any ideas? Thanks for all your help.

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