examples/extern_methods.nit

   1 # This file is part of NIT ( http://www.nitlanguage.org ).
   2 #
   3 # Copyright 2012 Alexis Laferrière <alexis.laf@xymus.net>
   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 # This module illustrates some uses of the native interface, specifically
  18 # how to use extern methods. Which means to implement a Nit method in C.
  19 #
  20 # Steps to use extern methods:
  21 # 1. Write the Nit module (like this file), define extern methods
  22 #    with "is extern" and identify possible callbacks with "import".
  23 # 2. Run ithe "nits" program on the Nit module, it will generate
  24 #    two files, extern_methods.stub.[ch] files.
  25 # 3. Modify those files to implement Nit methods in C.
  26 # 4. Rename the stub files to extern_methods.nit.c and extern_methods.nit.h.
  27 module extern_methods
  28
  29 redef enum Int
  30         # Returns self'th fibonnaci number
  31         # implemented here in C for optimization purposes
  32         fun fib : Int is extern
  33
  34         # System call to sleep for "self" seconds
  35         fun sleep is extern
  36
  37         # Return atan2l( self, x ) from libmath
  38         fun atan_with( x : Int ) : Float is extern
  39
  40         # This method callback to Nit methods from C code
  41         # It will use from C code:
  42         # * the local fib method
  43         # * the + operator, a method of Int
  44         # * to_s, a method of all objects
  45         # * String::to_cstring, a method of String to return an equivalent char*
  46         fun foo is extern import fib, +, to_s, String::to_cstring
  47
  48         # Equivalent to foo but written in pure Nit
  49         fun bar do print "from Nit: self + fib(self) = {self+self.fib}"
  50 end
  51
  52 print 12.fib
  53
  54 print "sleeping 1 second..."
  55 1.sleep
  56
  57 print 100.atan_with( 200 )
  58 8.foo
  59 8.bar
  60