Re: Macro defining macros...

[Gary V. Vaughan]

Hello Carlo,

Carlo Contavalli wrote:
> Hello, I'm not subscribed to the list (can you carbon copy
> my address when replying?) and couldn't find any reference 
> in the manual... 
> I'm trying to do something like:
> 
>   define(`macro1', `define(`macro2', `$0 -- $1 -- $2')')
>   macro1
>   macro2(foo, bar)

Positional parameters are expanded without regard to nested
quotes, so when macro1 is called $0, $1 and $2 are expanded
inside its body.

macro1
  => define(`macro2', `macro1 -- -- ')
  =>
macro2(foo, bar)
  => macro1 -- --
  => define(`macro2', `macro1 -- -- ') -- --
  =>  -- --

You can defer the expansion by obfuscating the parameters:

define(`macro1', `define(`macro2', `$'`0 -- $'`1 -- $'`2')')
macro1
  => define(`macro2', `$0 -- $1 -- $2')
  =>
macro2(foo, bar)
  => macro2 -- foo -- bar
  => macro2 -- -- -- foo -- bar
  => macro2 -- -- -- -- -- foo -- bar
  => ...

You can fix the infinite loop with a pushdef, or changequote.

HTH,
        Gary.
-- 
Gary V. Vaughan      ())_.  address@hidden,gnu.org}
Research Scientist   ( '/   http://tkd.kicks-ass.net
GNU Hacker           / )=   http://www.gnu.org/software/libtool
Technical Author   `(_~)_   http://sources.redhat.com/autobook

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