Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!elroy.jpl.nasa.gov!jpl-devvax!lwall
From: lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall)
Newsgroups: comp.lang.perl
Subject: Re: YAFR: nl_printf()
Message-ID: <11525@jpl-devvax.JPL.NASA.GOV>
Date: 21 Feb 91 01:12:12 GMT
References: <1991Feb11.113551.3857@robobar.co.uk>
Reply-To: lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall)
Organization: Jet Propulsion Laboratory, Pasadena, CA
Lines: 49

In article <1991Feb11.113551.3857@robobar.co.uk> ronald@robobar.co.uk (Ronald S H Khoo) writes:
: [ Yes, line-eater, this is *Yet* another feature request ]
: 
: I need nl_printf() -- my boss won't let me use perl without it.
: (We have lots of foreign customers, and they seem to want reports
:  written in a language that they can understand :-( )
: 
: Is there any chance of adding a position independent sprintf() to perl?
: Pretty please ?  With a lump of sugar on top ?
: 
: A simple %<digit>$format a'la X/Open nl_sprintf() where <digit> from
: 1 to 9 specifies which parameter (plus corresponding nl_printf()) would be
: adequate.  I've actually hacked do_sprintf to recognise and obey this
: format (diffs below) but I guess it really needs to be a separately named
: nl_{s,}printf()... (which nevertheless is meant to work with non-position
: specified args as well, to help with sanity...)
: 
: Anyone got any better ideas ?   Any chance of some "Official" solution ?

It seems that it's fairly easy to write a subroutine to do this:

#!/usr/bin/perl

sub nl_sprintf {
    local($f) = $_[0];
    local(@ix);
    local($ix) = 1;

    $f =~ s/%(\d\$)?([-+ #\d.]*[\w%])/push(@ix,$1||$ix++) if $2 ne '%';"%$2"/eg;
    sprintf($f, @_[@ix]);
}

print &nl_sprintf('%s %s %s'."\n", "one", "two", "three");
print &nl_sprintf('%3$s %2$s %1$s'."\n", "one", "two", "three");
print &nl_sprintf('%1$s %2$s %3$s'."\n", "one", "two", "three");
print &nl_sprintf('%3$s %2$s %s'."\n", "one", "two", "three");

prints

one two three
three two one
one two three
three two one

I'd probably choose some other character than $ to mark position selectors,
though, so that I could use double-quoted strings without backwacking
every $.  Maybe :.

Larry