From: WATANABE Hirofumi <eban@...>
Date: 2003-08-11T19:14:41+09:00
Subject: Re: win32api calling with doubles

Hi,

ROTH Jakub <jroth@csob.cz> writes:

> How does one declare and external function (in a DLL) for use with Ruby
> which requires doubles as parameters and likewise returns double as a
> result? Is there any good detailed doc/info on the web on this?

Win32API does not support double.

> I have a C fct declared as 
> 
> 	double jadd2( double a, double b )
> 
> and export it from a DLL it gets compiled into. I want to call it from Ruby.
> Import it into Ruby as:
> 
> 	jadd2 = Win32API.new('jadd.dll', 'jadd2', 'dd', 'd')
> 
> and call as
> 
> 	p jadd2.Call( 1.3, 2.4 )
> 
> the error is "in `Call': Wrong number of parameters: expected 0, got 2.
> (RuntimeError)"

Use Ruby/DL:

% cat foo.c
double foo(double a, double b)
{
    return a + b;
}
% gcc -mno-cygwin -shared foo.c -o foo.dll
% cat footest.rb
require 'dl/import'

module Foo
  extend DL::Importable
  dlload "foo"
  extern "double foo(double, double)"
end

p Foo.foo(1.1, 2.2)
% ruby footest.rb
3.3

-- 
eban