gistfile1.rb

def format(line, binding)
	pattern = /[[:alpha:]\$_][[:alnum:]_]*/
	line.gsub(pattern) {|match| replace(match,binding) }
end

def replace(match, binding)
	reserved_words = "alias,and,BEGIN,begin,break,case,class,def,defined?,do,else,elsif,END,end,ensure,false,for,if,in,module,next,nil,not,or,redo,rescue,retry,return,self,super,then,true,undef,unless,until,when,while,yield".split(",")
	if reserved_words.rindex match
		return match
	end

	type = eval("defined? #{match}", binding)
	case type
	when "local-variable"
		return eval(match, binding) || match
	else
		return match
	end
end

p = proc { |event, file, line_number, id, binding, classname|
	if event == "line"
		printf "%s:%-3d ", file, line_number
		line = IO.readlines(file)[line_number - 1].chomp
		printf "%-10s | %s\n", line, format(line, binding)
	end
}

set_trace_func p

def test
	x = 7
	puts x
end

x = 3
puts x
test

set_trace_func nil