Byte-compile constants in a function

Byte-compile constants in a function

[Joe Riel]

Is there a way to define constant/macros so that the value is expanded
during byte-compilation of a function that uses them?

For example, I want to do

(defconst  tag-prompt ?>)

(defun check (char) (eq char tag-prompt))

where the byte-compilation of check is the same as that of

(defun check (char) (eq char ?>))

-- 
Joe Riel

Re: Byte-compile constants in a function

[José A. Romero L.]

W dniu wtorek, 3 lipca 2012 18:57:12 UTC+2 użytkownik Joe Riel napisał:
> Is there a way to define constant/macros so that the value is expanded
> during byte-compilation of a function that uses them?
(...)

How about defining an inlined function that returns the constant
you need?

    (defsubst tag-prompt () ?>)

then:

    (defun check (char) (eq char (tag-prompt)))

a quick look at the byte-compiled code shows that the value
of (tag-prompt) is indeed inlined.

Cheers,
--
José A. Romero L.
escherdragon at gmail
"We who cut mere stones must always be envisioning cathedrals."
(Quarry worker's creed)

Re: Byte-compile constants in a function

[Joe Riel]

On Tue, 3 Jul 2012 13:26:13 -0700 (PDT)
José A. Romero L. <escherdragon@gmail.com> wrote:

> W dniu wtorek, 3 lipca 2012 18:57:12 UTC+2 użytkownik Joe Riel napisał:
> > Is there a way to define constant/macros so that the value is expanded
> > during byte-compilation of a function that uses them?
> (...)
> 
> How about defining an inlined function that returns the constant
> you need?
> 
>     (defsubst tag-prompt () ?>)
> 
> then:
> 
>     (defun check (char) (eq char (tag-prompt)))
> 
> a quick look at the byte-compiled code shows that the value
> of (tag-prompt) is indeed inlined.

Thanks, that does what I want.

-- 
Joe Riel

Re: Byte-compile constants in a function

[Stefan Monnier]

> (defconst  tag-prompt ?>)
> (defun check (char) (eq char tag-prompt))

You can do

   (eval-when-compile
     (defconst tag-prompt ?>))
   
   (defun check (char) (eq char (eval-when-compile tag-prompt)))


-- Stefan

Re: Byte-compile constants in a function

[Joe Riel]

On Wed, 04 Jul 2012 09:26:06 -0400
Stefan Monnier <monnier@iro.umontreal.ca> wrote:

> > (defconst  tag-prompt ?>)
> > (defun check (char) (eq char tag-prompt))
> 
> You can do
> 
>    (eval-when-compile
>      (defconst tag-prompt ?>))
>    
>    (defun check (char) (eq char (eval-when-compile tag-prompt)))
> 
> 
> -- Stefan

Thanks, that seems nicer than using defsubst.  Possibly with that
I'll finally understand what eval-when-compile is all about.

-- 
Joe Riel