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.