Re: [Chicken-hackers] [PATCH] add pathname-expand

[Felix Winkelmann]

>>
>> Well, if it is such a can of worms, then perhaps it's not such a great
>> thing to have, after all. There are so many special cases and platform
>> dependencies, that it actually confuses more than it helps.
> 
> Getting rid of it is the simplest approach.  There are other ones,
> though.  Here are some of them:
> 
> * move pathname-expand to an egg.  From users standpoint, I think it
>   won't make a big difference between having pathname-expand in the core
>   or in an egg.  It's something new anyway.  Having it as an egg can
>   actually be a win in the end: it would be available to older chickens
>   (although it wouldn't do anything, since pathname expansion is
>   implicit).  But at least applications wouldn't break on an "Unbound
>   variable: pathname-expand" error.  If pathname-expand is in the core,
>   programs that use it will have a hard dependency on CHICKEN 4.9.0.

Makes sense.

> 
> * make it simpler.  Only expand ~/user.  No ~user and no ~~whatever.

Also makes sense.

> 
> * to work around the issue "what to do when home cannot be determined",
>   an additional parameter to determine the default home directory (a
>   string) or behavior (a procedure).  Example:
> 
>   (define default-user-home-directory
>     (make-parameter "/"))
> 
>   (define (pathname-expand path)
>     (if (home-is-defined?)
>         (do-expand path)
>         (if (procedure? (default-user-home-directory))
>             ((default-user-home-directory) path)
>             (do-expand path (default-user-home-directory)))))
> 
>   If default-user-home-directory can be a procedure, users may 
>   decide what to do when no home is defined.

Hm. One more option. I'm not sure if this isn't perhaps too much choice.

> Personally, I'd vote for leaving it out of the core and eventually
> implement it as an egg, when we have a consensus on what it should do.

Good idea.


felix