examples/fibonacci.nit

   1 # This file is part of NIT ( http://www.nitlanguage.org ).
   2 #
   3 # Copyright 2004-2008 Jean Privat <jean@pryen.org>
   4 #
   5 # Licensed under the Apache License, Version 2.0 (the "License");
   6 # you may not use this file except in compliance with the License.
   7 # You may obtain a copy of the License at
   8 #
   9 #     http://www.apache.org/licenses/LICENSE-2.0
  10 #
  11 # Unless required by applicable law or agreed to in writing, software
  12 # distributed under the License is distributed on an "AS IS" BASIS,
  13 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14 # See the License for the specific language governing permissions and
  15 # limitations under the License.
  16
  17 # A simple exemple of refinement where a method is added to the integer class.
  18 module fibonacci
  19
  20 redef class Int
  21         # Calculate the self-th element of the fibonacci sequence.
  22         fun fibonacci: Int
  23         do
  24                 if self < 2 then
  25                         return 1
  26                 else
  27                         return (self-2).fibonacci + (self-1).fibonacci
  28                 end
  29         end
  30 end
  31
  32 # Print usage and exit.
  33 fun usage
  34 do
  35         print "Usage: fibonnaci <integer>"
  36         exit 0
  37 end
  38
  39 # Main part
  40 if args.length != 1 then
  41         usage
  42 end
  43 print args.first.to_i.fibonacci