trace.rb

# Function to print hierarchical call trees as the program executes.
# Use "ir.exe -trace" for IronRuby

$CALL_DEPTH = 0
p = proc { |op, file, line, method, b, cls|
    if op == "call"
      filename = file.nil? ? nil : file.gsub('\\','/')
      puts "#{$CALL_DEPTH}\t" + ('| ' * $CALL_DEPTH) + "> #{cls}::#{method}         #{filename}:#{line}"
      locals = eval("local_variables", b)
      local_values = locals.each { |l| 
        val = nil
        begin
          val = eval(l, b)
        rescue
        end
        puts "#{$CALL_DEPTH}\t" + ('| ' * $CALL_DEPTH) + "      #{l}:#{val.inspect}"
      }
      $CALL_DEPTH += 1
    elsif op == "return"  
      $CALL_DEPTH -= 1 if $CALL_DEPTH > 0
    elsif op == "raise"
      puts "$!" * 20
    end
}

set_trace_func p

# A simpler solution is:
# set_trace_func proc { |*args| p args }