coerce_to

# File lib/matrix.rb, line 1399
    def self.coerce_to(obj, cls, meth) # :nodoc:
      return obj if obj.kind_of?(cls)

      begin
        ret = obj.__send__(meth)
      rescue Exception => e
        raise TypeError, "Coercion error: #{obj.inspect}.#{meth} => #{cls} failed:\n"                           "(#{e.message})"
      end
      raise TypeError, "Coercion error: obj.#{meth} did NOT return a #{cls} (was #{ret.class})" unless ret.kind_of? cls
      ret
    end