if3 as canonical macro

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From:

David L. Nicol

Date:

August 1, 2001 12:36

Subject:

if3 as canonical macro

Message ID:

3B685826.4268389C@kasey.umkc.edu



> > sub if3 ($&&&) {
> >   return &{$_[1]} unless $_[0];
> >   return &{$_[2]} if $_[0] < 0;
> >   return &{$_[3]};
> > }
> >
> > gives the functionality.

How about allowing a scheme-style macro specifier:

	macro if3 ($&&&) {
	  return &{$_[1]} unless $_[0];
	  return &{$_[2]} if $_[0] < 0;
	  return &{$_[3]};
	}

So, it gets inline-expanded instead of called. Then
it might be (with a  -1, 0, +1 selection order)

	macro if3 ($&&&) { $_[0] ? ( $_[0] < 0 ? &$[1] : &$[3] ) : &$[2] }

I think it would be a really good example of a macro, for the documentaion
of macros, or inlined subroutines (in the C++ inline sense, not the
Inline.pm
sense), or whatever they might get called.

Or maybe the internals might replace all one-expression subs in place
instead of calling them, which could be abused by wrapping the whole
subroutined body in a do or an eval.


-- 
                                           David Nicol 816.235.1187
 "Straight from the docs" doesn't mean "you can cut-and-paste" - it
      just means you find the principle explained clearly - without
             having to construct it from smaller blocks. -- Abigail

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