From: Michael Strelnikov <michaelst@...>
Date: 2007-03-12T12:56:26+09:00
Subject: Re: #define alternative for Ruby

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On 3/12/07, Timothy Hunter <TimHunter@nc.rr.com> wrote:
>
> Mike wrote:
> > On Mar 12, 1:52 am, Daniel Berger <djber...@gmail.com> wrote:
> >
> >> Michael Strelnikov wrote:
> >>
> >>> Hello all,
> >>>
> >>>   Does Ruby have something like "#define" for C/C++? Especially with
> >>> arguments like "#define foo(x) (something_done_with_x(x))".
> >>>
> >>>   Please don't say that "def" do the same. It doesn't.
> >>>
> >> The closest analogue is to conditionally define a constant, then used
> >> defined? on that constant.
> >>
> >> For example, I do something like this in the windows-pr project, where
> >> some methods are not supported by Win2k or earlier:
> >>
> >> module Windows
> >>    module Console
> >>      begin
> >>        AttachConsole = Win32API.new('kernel32','AttachConsole','L',
> 'I')
> >>      rescue LoadError
> >>        # Requires Windows XP or later
> >>      end
> >>    end
> >> end
> >>
> >> And then, while using the above module:
> >>
> >> class MyConsoleClass
> >>     include Windows::Console
> >>
> >>     def test
> >>        if defined? AttachConsole
> >>           # do something
> >>        else
> >>           # do something else
> >>        end
> >>     end
> >> end
> >>
> >> Regards,
> >>
> >> Dan
> >>
> >
> > I was talking more about macros rather then constants.
> > But I agree that constant are convenient way to substitute "#define
> > myconst 15". But can you substitute "#define myfunc(x)
> > (sin(x)*cos(x)*exp(x))"?
> > You should know that "x" could be as much other functions as a
> > constant/variable.
> >
>
> I would be interested in hearing what you want to do with text
> substitution that you cannot already do with standard Ruby
> metaprogramming techniques.
>
>
Easy.
Let's we have following function:
* set_default(var, val)
-- if variable "var" is not defined (not existed) then assign value "val"
else do nothing.

The variable could be ANY type including "Fixnum".

Try to implement it using standard techniques.

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