special forms

special forms

[A Soare]

I do not find in Feval where the `special forms' are treated. Can somebody help me please?

Re: special forms

[John Paul Wallington]

A Soare <alinsoar@voila.fr> writes:

> I do not find in Feval where the `special forms' are treated. Can somebody help me please?

It looks like from line 2272 or so in the current sources of eval.c:

      if (XSUBR (fun)->max_args == UNEVALLED)
        {
          backtrace.evalargs = 0;
          val = (*XSUBR (fun)->function) (args_left);
          goto done;
        }

Does that help?

Re: special forms

[A Soare]

I do not find in Feval where the `special forms' are treated. Can somebody help me please?

A Soare <alinsoar@...> writes:

> I do not find in Feval where the `special forms' are treated. Can somebody help me please?

It looks like from line 2272 or so in the current sources of eval.c:

      if (XSUBR (fun)->max_args == UNEVALLED)
        {
          backtrace.evalargs = 0;
          val = (*XSUBR (fun)->function) (args_left);
          goto done;
        }

>Does that help? 

Thanks. 

I do not knot yet... What is the difference between SUBRP and XSUBR ?

Alin Soare.

Re: special forms

[A Soare]

I do not find in Feval where the `special forms' are treated. Can somebody help me please?

A Soare <alinsoar@...> writes:

> I do not find in Feval where the `special forms' are treated. Can somebody help me please?

It looks like from line 2272 or so in the current sources of eval.c:

      if (XSUBR (fun)->max_args == UNEVALLED)
        {
          backtrace.evalargs = 0;
          val = (*XSUBR (fun)->function) (args_left);
          goto done;
        }

>Does that help? 

I looked closely. We got it.


"UNEVALLED" indicate that the evaluation of a function must mut evaluate its arguments.

Thanks a lot.


Alin Soare.

Re: special forms

[Karl Hegbloom]

On Wed, 2007-04-18 at 21:40 +0200, A Soare wrote:
> I do not knot yet... What is the difference between SUBRP and XSUBR ?

The naming convention is that the macro or function ending in 'p' is a
predicate.  It's asking the yes or no question "is this lisp object a
'subr'?"  It looks in the Lisp object's type field, and checks to see if
it's type is 'subr'.  The macros that start with 'X' are accessors, the
mnemonic being that "X" sounds like "access".  It is accessing and
returning the location of the C routine that implements the Lisp subr.