Expr(3) User Contributed Perl Documentation Expr(3)NAMEHTML::Template::Expr - HTML::Template extension adding expression
support
SYNOPSIS
use HTML::Template::Expr;
my $template = HTML::Template::Expr->new(filename => 'foo.tmpl');
$template->param(banana_count => 10);
print $template->output();
DESCRIPTION
This module provides an extension to HTML::Template which allows
expressions in the template syntax. This is purely an addition - all
the normal HTML::Template options, syntax and behaviors will still
work. See HTML::Template for details.
Expression support includes comparisons, math operations, string
operations and a mechanism to allow you add your own functions at
runtime. The basic syntax is:
<TMPL_IF EXPR="banana_count > 10">
I've got a lot of bananas.
</TMPL_IF>
This will output "I've got a lot of bananas" if you call:
$template->param(banana_count => 100);
In your script. <TMPL_VAR>s also work with expressions:
I'd like to have <TMPL_VAR EXPR="banana_count * 2"> bananas.
This will output "I'd like to have 200 bananas." with the same param()
call as above.
MOTIVATION
Some of you may wonder if I've been replaced by a pod person. Just for
the record, I still think this sort of thing should be avoided.
However, I realize that there are some situations where allowing the
template author some programatic leeway can be invaluable.
If you don't like it, don't use this module. Keep using plain ol'
HTML::Template - I know I will! However, if you find yourself needing
a little programming in your template, for whatever reason, then this
module may just save you from HTML::Mason.
BASIC SYNTAX
Variables are unquoted alphanumeric strings with the same restrictions
as variable names in HTML::Template. Their values are set through
param(), just like normal HTML::Template variables. For example, these
two lines are equivalent:
<TMPL_VAR EXPR="foo">
<TMPL_VAR NAME="foo">
Numbers are unquoted strings of numbers and may have a single "." to
indicate a floating point number. For example:
<TMPL_VAR EXPR="10 + 20.5">
String constants must be enclosed in quotes, single or double. For
example:
<TMPL_VAR EXPR="sprintf('%d', foo)">
You can string together operators to produce complex booleans:
<TMPL_IF EXPR="(foo || bar || baz || (bif && bing) || (bananas > 10))">
I'm in a complex situation.
</TMPL_IF>
The parser is pretty simple, so you may need to use parenthesis to get
the desired precedence.
COMPARISON
Here's a list of supported comparison operators:
· Numeric Comparisons
· <
· >
· ==
· !=
· >=
· <=
· <=>
· String Comparisons
· gt
· lt
· eq
· ne
· ge
· le
· cmp
MATHEMATICS
The basic operators are supported:
· +
· -
· *
· /
· %
There are also some mathy functions. See the FUNCTIONS section below.
LOGIC
Boolean logic is available:
· && (synonym: and)
· || (synonym: or)
FUNCTIONS
The following functions are available to be used in expressions. See
perldoc perlfunc for details.
· sprintf
· substr (2 and 3 arg versions only)
· lc
· lcfirst
· uc
· ucfirst
· length
· defined
· abs
· atan2
· cos
· exp
· hex
· int
· log
· oct
· rand
· sin
· sqrt
· srand
All functions must be called using full parenthesis. For example, this
is a syntax error:
<TMPL_IF expr="defined foo">
But this is good:
<TMPL_IF expr="defined(foo)">
DEFINING NEW FUNCTIONS
To define a new function, pass a "functions" option to new:
$t = HTML::Template::Expr->new(filename => 'foo.tmpl',
functions =>
{ func_name => \&func_handler });
Or, you can use "register_function" class method to register the
function globally:
HTML::Template::Expr->register_function(func_name => \&func_handler);
You provide a subroutine reference that will be called during output.
It will recieve as arguments the parameters specified in the template.
For example, here's a function that checks if a directory exists:
sub directory_exists {
my $dir_name = shift;
return 1 if -d $dir_name;
return 0;
}
If you call HTML::Template::Expr->new() with a "functions" arg:
$t = HTML::Template::Expr->new(filename => 'foo.tmpl',
functions => {
directory_exists => \&directory_exists
});
Then you can use it in your template:
<tmpl_if expr="directory_exists('/home/sam')">
This can be abused in ways that make my teeth hurt.
MOD_PERL TIP
"register_function" class method can be called in mod_perl's startup.pl
to define widely used common functions to HTML::Template::Expr. Add
something like this to your startup.pl:
use HTML::Template::Expr;
HTML::Template::Expr->register_function(foozicate => sub { ... });
HTML::Template::Expr->register_function(barify => sub { ... });
HTML::Template::Expr->register_function(baznate => sub { ... });
You might also want to pre-compile some commonly used templates and
cache them. See HTML::Template's FAQ for instructions.
CAVEATS
Currently the module forces the HTML::Template global_vars option to be
set. This will hopefully go away in a future version, so if you need
global_vars in your templates then you should set it explicitely.
The module won't work with HTML::Template's file_cache or shared_cache
modes, but normal memory caching should work. I hope to address this
is a future version.
The module is inefficient, both in parsing and evaluation. I'll be
working on this for future versions and patches are always welcome.
BUGS
I am aware of no bugs - if you find one, join the mailing list and tell
us about it. You can join the HTML::Template mailing-list by visiting:
http://lists.sourceforge.net/lists/listinfo/html-template-users
Of course, you can still email me directly (sam@tregar.com) with bugs,
but I reserve the right to forward bug reports to the mailing list.
When submitting bug reports, be sure to include full details, including
the VERSION of the module, a test script and a test template
demonstrating the problem!
CREDITS
The following people have generously submitted bug reports, patches and
ideas:
Peter Leonard
Tatsuhiko Miyagawa
Don Brodale
Thanks!
AUTHOR
Sam Tregar <sam@tregar.com>
LICENSEHTML::Template::Expr : HTML::Template extension adding expression
support
Copyright (C) 2001 Sam Tregar (sam@tregar.com)
This module is free software; you can redistribute it and/or modify it
under the terms of either:
a) the GNU General Public License as published by the Free Software
Foundation; either version 1, or (at your option) any later version, or
b) the "Artistic License" which comes with this module.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See either the
GNU General Public License or the Artistic License for more details.
You should have received a copy of the Artistic License with this
module, in the file ARTISTIC. If not, I'll be glad to provide one.
You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
POD ERRORS
Hey! The above document had some coding errors, which are explained
below:
Around line 496:
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Around line 536:
=back doesn't take any parameters, but you said =back 4
Around line 550:
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Around line 599:
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perl v5.14.1 2006-04-18 Expr(3)
