Re: Need help with macro

[Alex Vong]

Hello Mike,

Mike Gran <address@hidden> writes:

> Hey all,
>
> I need help making a macro.
>
> I have an existing procedure of the form
>
> (call-method self method (...))
>
> Note that SELF is a struct, METHOD is a string, and the ellipses can
> be anything.
>
> I would like to make a macro that transforms into the above, but, is
> of the form
>
> (send self (method ...))
>
> where SELF is the same struct, METHOD is a literal symbol, and the
> ellipses are unchanged.
>
> For example, I would like to call
>
> (send date (get-year))
> (send date (set-year 2018))
> (send date (set-dmy 1 1 2018))
>
> and have it be
>
> (call-method date "get-year" '())
> (call-method date "set-year" (list 2018))
> (call-method date "set-dmy" (list 1 1 2018))
>
> I get hung up on figuring out how to handle the literal symbol and the
> ellipses.
>
> If you need context, see
> https://wiki.gnome.org/Projects/GObjectIntrospection/HowToWriteALanguageBinding
>
> Thanks in advance,
>
> Mike Gran

I think this would work:

  (define-syntax-rule (send self (method args ...))
    (call-method self
                 (symbol->string 'method)
                 (list args ...)))

For example,

  (send date (set-dmy 1 1 2018))

will be expanded to

  (call-method date
               (symbol->string 'set-dmy)
               (list 1 1 2018))

which is equivalent to

  (call-method date "set-dmy" (list 1 1 2018))

Cheers,
Alex

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