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["Sam Liddicott" <address@hidden>]

On 08/04/11 08:47, Sam Liddicott wrote:
> Nope... my version will also eval the args...
>
> even this one will eval the args!!! - but is perhaps neater than the 
> map-args version
>
> <assign|tt|<xmacro|x|<quasiquote|<length|<tuple|<unquote*|<quote-arg|x>>>>>>> 
>
>
> or.... maybe I can't really tell... I don't know when a macro gets 
> evaluated I think... I used to think it was as late as possible, maybe 
> it is as soon as possible?
>
> agghg

This test shows that macros are evaluated as late as possible:

<assign|tt|<xmacro|x|<quasi|<length|<tuple|dup|<unquote*|<quote-arg|x>>|<unquote*|<quote-arg|x>>>>>>>

<assign|ix|<macro|<assign|x|<plus|<value|x>|1>>d>>

<assign|x|0>

<tt|<ix|a|b|c>>

<value|x>

clearly <ix|...> is passed un-evaluated to tt, which - despite the 
quote-arg still manages to evaluate before it can count.

BUT THIS VERSION DOES WORK:

<assign|tt|<xmacro|x|<quasiquote|<get-arity|<quote-arg|x>>>>>

Sam

> Sam
>
> On 08/04/11 08:02, Sam Liddicott wrote:
> > To follow on from yesterdays message:
> >
> > I can't believe I just got this to work! (I typed it in a text editor 
> > and cut-n-paste to texmacs in one go).
> >
> > <assign|tt|<xmacro|x|<get-arity|<eval-args|x>>>>
> >
> > I have a use of eval-args that doesn't segfault!
> >
> > However I think it is not a good way to get the number of arguments 
> > passed to a variable macro, if the arguments have a side-effect (like 
> > increasing a counter or setting global variables) then eval-args will 
> > cause the side effect.
> >
> > This macro will also give the number of arguments. I hope there is a 
> > better way than this though
> >
> > <assign|ll|<xmacro|x|<length|<map-args|identity|tuple|x>>>>
> >
> >
> >
> > I tried this, but it also segfaults
> >
> > <assign|ll|<xmacro|x|<length|x>>>
> >
> > I also tried something like this but it seg-faults:
> >
> > <assign|ll|<xmacro|x|<quasi|<length|<tuple|<unquote*|<arg|x>>>>>>>
> >
> >
> >
> > Sam
> >
> > On 07/04/11 22:12, Jan Lellmann wrote:
> > > Hello,
> > >
> > > the following code reproducibly produces segfaults when I move the 
> > > cursor to the "x" inside the macro.
> > >
> > > This is bad, since it is the only way to get the number of arguments 
> > > passed to a variable macro.
> > >
> > > ----
> > > <TeXmacs|1.0.7.3>
> > >
> > > <style|generic>
> > >
> > > <\body>
> > > <xmacro|x|<get-arity|<eval-args|x>>>
> > > </body>
> > >
> > > <\initial>
> > > <\collection>
> > > <associate|language|american>
> > > <associate|page-type|letter>
> > > <associate|preamble|true>
> > > </collection>
> > > </initial>
> > > ----
> > >
> > > Any ideas why?
> > >
> > > Jan


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