gistfile1.rb

require "tcl"

module Tcl
  class ExprEvaluator
    def initialize
      @interp = Tcl::SafeInterp.new
      commands = @interp.list_to_array(@interp._!(:info, :commands)) - %w(info set unset rename expr)
      (commands + %w(rename)).each { |command| @interp._!(:rename, command, "") }
    end
    
    def evaluate(expression, variables = {})
      load!(variables)
      @interp._!(:expr, expression)
    end
    
    protected
      def unset_all_globals!
        vars = @interp.list_to_array(@interp._!(:info, :globals))
        vars.each { |var| @interp._!(:unset, var) }
      end
      
      def load!(variables)
        unset_all_globals!
        variables.each { |var, value| @interp._!(:set, var, value) }
      end
  end
end