From: Ben Giddings <ben@...>
Date: 2003-08-01T11:29:34+09:00
Subject: ANN: debugprint

Hi everybody,

Growing out of the discussions about $DEBUG and $VERBOSE, and how 
they're set from the commandline, I've created a dead-simple 
"debugprint" library package.  You can find it on RAA at:


But since it's so tiny, here's the entire code:

module Kernel
   def info(*args)
     puts(*args) if $VERBOSE
   end

   def debug(*args)
     puts(*args) if $DEBUG
   end

   module_function :info, :debug
end

This time, I actually followed the KISS principle.  :)

I'm hoping this can save a few keystrokes in its current form.  But I 
also have visions for something more ambitious, so I'd like to discuss 
a little.

In C, I have some debug macros that look like this:

#define printlnDebug(fmt, ...) \
printf("[D]%s#%s:%d " fmt "\n", __FILE__, __FUNCTION__, __LINE__, 
__VA_ARGS__)

#define printvarDebug(var) \
printf("[D]%s#%s:%d %s=%d\n", __FILE__, __FUNCTION__, __LINE__, #var, 
var)

The end result is that if I have these lines of c code:

state = "running";
count = 5;
printlnDebug("state is: %s", state);
printvarDebug(count);

I get this result:

[D]main.c#doSomething:80 state is: running
[D]main.c#doSomething:81 count=5

I have ambitions to do something similar with Ruby.  My idea is that 
you could set a format string, similar to the one in the Time class and 
use that when you print out debug info, the default format string would 
simply include the debug message.

So, some questions:
1) is it possible for a method to get access to the context that called 
it so it can fill in things like source file name, method name, and 
line number
2) is there a way to get the name of a variable into a string, like the 
#var construct does in C macros

Could the ruby commandline syntax be modified so that they can do more 
than just set $DEBUG and $VERBOSE to true/false?  For example, maybe 
allowing multiple flags so that -ddd (or -d -d -d) would set $DEBUG to 
3.  Or, possibly adding an optional parameter with the same syntax as 
the -e flag that would allow you to set $DEBUG or $VERBOSE to any value 
you want.  As others have mentioned, these changes would keep backwards 
compatibility with scripts that say "if $DEBUG", which seems to be the 
most common usage.  On the other hand, might they have an effect on 
other things, like C code that compiles to a Ruby library.  I have no 
idea how $DEBUG and $VERBOSE are used here.

Comments?

Ben