From: Paul Brannan <pbrannan@...>
Date: 2004-08-04T11:59:41+09:00
Subject: Re: Macros in Ruby

On Wed, Aug 04, 2004 at 09:15:25AM +0900, Ben Giddings wrote:
> The one place I've really missed macros is in debugging.  I'm really 
> used to C macros that are really simple to type 'dbg(val);' but can 
> produce detailed valuable output:
> 
> foo.c:132 do_it() val => 23

This looks more like logging than debugging.  C macros typically make
debugging more difficult, not less, because most debuggers don't let you
"step into" a macro like you can with a function.

> There are hackish ways to get something approaching this in Ruby, mainly 
> by twiddling with the 'caller' array, and using symbols to grab the name 
> of the symbol along with its value.  That feels really hackish to me. 
> I'd feel slightly better about it if callers returned an array of 
> "SourceLine" objects, or something, and you could get the method name as 
> well.  But it's still not quite up there with the ease of use of a C macro.

The caller() method certainly has its problems.  The API could be easier
to use, but that doesn't make C macros better.  You are comparing the
design of two APIs (the Ruby API and the C preprocessor API), not macros
versus no-macros.

> I don't know if there's a middle ground, but I certainly lean towards 
> avoiding macros.

What experience do you have with lisp macros or other non-C-preprocessor
macros?

Paul