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NAME
Text::sprintfn - Drop-in replacement for sprintf(), with named parameter
support
VERSION
version 0.06
SYNOPSIS
use Text::sprintfn; # by default exports sprintfn() and printfn()
# with no hash, behaves just like printf
printfn '<%04d>', 1, 2; # <0001>
# named parameter
printfn '<%(v1)-4d>', {v1=>-2}; # <-2 >
# mixed named and positional
printfn '<%d> <%(v1)d> <%d>', {v1=>1}, 2, 3; # <2> <1> <3>
# named width
printfn "<%(v1)(v2).1f>", {v1=>3, v2=>4}; # < 3>
# named precision
printfn "<%(v1)(v2).(v2)f>", {v1=>3, v2=>4}; # <3.0000>
DESCRIPTION
This module provides sprintfn() and printfn(), which are like sprintf()
and printf(), with the exception that they support named parameters from
a hash.
FUNCTIONS
sprintfn $fmt, \%hash, ...
If first argument after format is not a hash, sprintfn() will behave
exactly like sprintf().
If hash is given, sprintfn() will look for named parameters in argument
and supply the values from the hash. Named parameters are surrounded
with parentheses, i.e. "(NAME)". They can occur in format parameter
index:
%2$d # sprintf version, take argument at index 2
%(two)d # $ is optional
%(two)$d # same
or in width:
%-10d # sprintf version, use (minimum) width of 10
%-(width)d # like sprintf, but use width from hash key 'width'
%(var)-(width)d # format hash key 'var' with width from hash key 'width'
or in precision:
%6.2f # sprintf version, use precision of 2 decimals
%6.(prec)f # like sprintf, but use precision from hash key 'prec'
%(width).(prec)f
%(var)(width).(prec)f
The existence of formats using hash keys will not affect indexes of the
rest of the argument, example:
sprintfn "<%(v1)s> <%2$d> <%d>", {v1=>10}, 0, 1, 2; # "<10> <2> <0>"
Like sprintf(), if format is unknown/erroneous, it will be printed
as-is.
There is currently no way to escape ")" in named parameter, e.g.:
%(var containing ))s
printfn $fmt, ...
Equivalent to: print sprintfn($fmt, ...).
RATIONALE
There exist other CPAN modules for string formatting with named
parameter support. Two of such modules are String::Formatter and
Text::Sprintf::Named. This module is far simpler to use and retains all
of the features of Perl's sprintf() (which we like, or perhaps hate, but
nevertheless are familiar with).
String::Formatter requires you to create a new formatter function first.
Text::Sprintf::Named also accordingly requires you to instantiate an
object first. There is currently no way to mix named and positional
parameters. And you don't get the full features of sprintf().
HOW IT WORKS
Text::sprintfn works by converting the format string into sprintf
format, i.e. replacing the named parameters like "%(foo)s" to something
like "%11$s".
DOWNSIDES
Currently the main downside is speed. On my computer, sprintfn() is
about two orders of magnitude slower than plain sprintf(). A simple
benchmark on my PC (Core i5-2400 @ 3.1GHz):
$ bench -MText::sprintfn -n -2 'sprintf("%s %d %d", "one", 2, 3)' 'sprintfn("%(str)s %d %d", {str=>"one"}, 2, 3)'
Benchmarking a => sub { sprintf("%s %d %d", "one", 2, 3) }, b => sub { sprintfn("%(str)s %d %d", {str=>"one"}, 2, 3) } ...
a: 13666654 calls (6831551/s), 2.001s (0.0001ms/call)
b: 72461 calls (35045/s), 2.068s (0.0285ms/call)
Fastest is a (194.9x b)
TIPS AND TRICKS
Common mistake 1
Writing
%(var)
instead of
%(var)s
Common mistake 2 (a bit more newbish)
Writing
sprintfn $format, %hash, ...;
instead of
sprintfn $format, \%hash, ...;
Alternative hashes
You have several hashes (%h1, %h2, %h3) which should be consulted for
values. You can either merge the hash first:
%h = (%h1, %h2, %h3); # or use some hash merging module
printfn $format, \%h, ...;
or create a tied hash which can consult hashes for you:
tie %h, 'Your::Module', \%h1, \%h2, \%h3;
printfn $format, \%h, ...;
TODOS
Some sort of caching.
SEE ALSO
sprintf() section on perlfunc
String::Formatter
Text::Sprintf::Named
AUTHOR
Steven Haryanto <stevenharyanto@gmail.com>
COPYRIGHT AND LICENSE
This software is copyright (c) 2012 by Steven Haryanto.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
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