Re: Help! Strings -> Numbers

On Thursday, November 21, 2002, at 12:16  AM, Dave Storrs wrote:
> I do agree that having it be a method (and hence overloadable) is the
> best solution.  I just wish there were some way to get away from those
> dratted sprintf format strings.

Amen.  God, I've hated those things for years.  And yet most attempts I 
make at something just as powerful begins to look an awful lot like it 
anyway.

I keep musing over possible scenarios, two in particular:

1) "Formats" as classes.  What I _want_ to do is to be able to 
associate a named "format" with a given class/instance/output, because 
I tend to use the same few formats over and over.  So if I want to 
frequently output numbers as '%-4.2d', I just call it "MoneyFormat" or 
something:

   class MoneyFormat is NumFormat {
     sub width     { 4 };
     sub precision { 2 };
     sub align     { 'right' };
   }

   And then later I can say things like:

    print $v.as(MoneyFormat);      # just pass the class name
    print $v.as(MoneyFormat.new);  # or a specific instance

and not deal with sprintf syntax at all, but still have something 
that's eminently adjustable, self-documenting, and has decent 
compile-time optimization possibilities.  And could change, runtime, 
according to user preferences.

2) An analogue to a "rule", but for output instead of input.  As we can 
say:

    $s ~~ /<number>/

if we've defined a rule called <number>, it feels like it would be 
useful to allow similar "output rules" that format things for 
interpolation.  Like:

    print "blah blah: <$i:MoneyFormat>";

But that would mean you couldn't use literal < > in interpolated 
strings, which might be a pain in todays XML-centric world.  I like the 
general "output rule" idea a lot, though, because it represents how you 
typically use formatting -- inside a larger interpolation.

It would be very useful in the second half of a s///, too (grab a 
match, rewrite it in a canonical form):

     $s ~~ s/<number>/<number:MoneyFormat>/;

Or something like that.  I know I'm stream-of-conciousnessing here, it 
just feels like we're missing something...

MikeL