Re: new function

[Taylan Kammer]

On 22.09.2021 23:52, William ML Leslie wrote:
> On Thu, 23 Sep 2021, 4:51 am Taylan Kammer, <taylan.kammer@gmail.com 
> <mailto:taylan.kammer@gmail.com>> wrote:
> 
>     On 22.09.2021 11:53, Damien Mattei wrote:
>     > i already do it this way for internal defines ,using a recursive macro 
> that build a list of variable using an accumulator. It can works but macro 
> expansion seems slow, it was not immediate at compilation on a little example 
> (oh nothing more that 2 seconds) but i'm not sure it is easily maintainable, 
> it is at the limit what macro can do i think ,for speed reasons. In fact i 
> can not really understand in Guile as it is based on C and compiled when 
> macro expansion happens,what is the time cost... so for all those ,perhaps 
> not objective reason ,i prefer to avoid.
> 
>     I don't think there's any other way to achieve what you want, especially
>     using portable Scheme code.  The lexical scoping semantics of Scheme are
>     a very fundamental part of the language, and cannot be worked around in
>     portable Scheme code without using a macro that rewrites whole bodies of
>     lambda expressions.
> 
>     Even using implementation-specific hacks, you won't get very far.  Any
>     compiled Scheme implementation, and even most interpreted ones, won't
>     allow you to modify an outer scope's set of variable definitions from
>     within an inner scope.
> 
>     So if you really want to have Python's scoping semantics in Scheme, you
>     will probably have to write a complex 'def' macro that walks through the
>     body and "hoists" variable definitions to the outermost scope.
> 
> 
> Python is lexically scoped, and the assignment here is supposed to be local.

Well, yes and no.  It implements variable hoisting, meaning all previously
unset variables that are set within a function are implicitly declared at the
beginning of the function.  It doesn't have sub-scopes in function bodies.

-- 
Taylan