NAME

Template::Alloy::TT - Template::Toolkit role

DESCRIPTION

The Template::Alloy::TT role provides the syntax and the interface for Template::Toolkit version 1, 2, and 3. It also brings many of the features from the various templating systems.

And it is fast.

See the Template::Alloy documentation for configuration and other parameters.

HOW IS Template::Alloy DIFFERENT FROM Template::Toolkit

Alloy uses the same base template syntax and configuration items as TT2, but the internals of Alloy were written from scratch. Additionally much of the planned TT3 syntax is supported as well as most of that of HTML::Template::Expr. The following is a list of some of the ways that the configuration and syntax of Alloy are different from that of TT2. Note: items that are planned to work in TT3 are marked with (TT3).

Numerical hash keys work
```
    [% a = {1 => 2} %]
    
```
Quoted hash key interpolation is fine
```
    [% a = {"$foo" => 1} %]
    
```
Multiple ranges in same constructor
```
    [% a = [1..10, 21..30] %]
    
```

Constructor types can call virtual methods. (TT3)

    [% a = [1..10].reverse %]

    [% "$foo".length %]

    [% 123.length %]   # = 3

    [% 123.4.length %]  # = 5

    [% -123.4.length %] # = -5 ("." binds more tightly than "-")

    [% (a ~ b).length %]

    [% "hi".repeat(3) %] # = hihihi

    [% {a => b}.size %] # = 1

The "${" and "}" variable interpolators can contain expressions, not just variables.

    [% [0..10].${ 1 + 2 } %] # = 4

    [% {ab => 'AB'}.${ 'a' ~ 'b' } %] # = AB

    [% color = qw/Red Blue/; FOR [1..4] ; color.${ loop.index % color.size } ; END %]
      # = RedBlueRedBlue

You can use regular expression quoting.

    [% "foo".match( /(F\w+)/i ).0 %] # = foo

Tags can be nested.

    [% f = "[% (1 + 2) %]" %][% f|eval %] # = 3

Arrays can be accessed with non-integer numbers.
```
    [% [0..10].${ 2.3 } %] # = 3
    
```

Reserved names are less reserved. (TT3)

    [% GET GET %] # gets the variable named "GET"

    [% GET $GET %] # gets the variable who's name is stored in "GET"

Filters and SCALAR_OPS are interchangeable. (TT3)

    [% a | length %]

    [% b . lower %]

Pipe "|" can be used anywhere dot "." can be and means to call the virtual method. (TT3)

    [% a = {size => "foo"} %][% a.size %] # = foo

    [% a = {size => "foo"} %][% a|size %] # = 1 (size of hash)

Pipe "|" and "." can be mixed. (TT3)

    [% "aa" | repeat(2) . length %] # = 4

Added V2PIPE configuration item

Restores the behavior of the pipe operator to be compatible with TT2.

With V2PIPE = 1

    [% PROCESS a | repeat(2) %] # = value of block or file a repeated twice

With V2PIPE = 0 (default)

    [% PROCESS a | repeat(2) %] # = process block or file named a ~ a

Added V2EQUALS configuration item

Allows for turning off TT2 "==" behavior. Defaults to 1 in TT syntaxes and to 0 in HT syntaxes.

    [% CONFIG V2EQUALS => 1 %][% ('7' == '7.0') || 0 %]
    [% CONFIG V2EQUALS => 0 %][% ('7' == '7.0') || 0 %]

Prints

    0
    1

Added AUTO_EVAL configuration item.
Default false. If true, will automatically call eval filter on double quoted strings.
Added SHOW_UNDEFINED_INTERP configuration item.
Default false. If true, will leave in place interpolated values that weren't defined. You can then use the Velocity notation $!foo to not show these values.

Added Virtual Object Namespaces. (TT3)

The Text, List, and Hash types give direct access to virtual methods.

    [% a = "foobar" %][% Text.length(a) %] # = 6

    [% a = [1 .. 10] %][% List.size(a) %] # = 10

    [% a = {a=>"A", b=>"B"} ; Hash.size(a) %] = 2

    [% foo = {a => 1, b => 2}
       | Hash.keys
       | List.join(", ") %] # = a, b

Added "fmt" scalar, list, and hash virtual methods.

    [% list.fmt("%s", ", ") %]

    [% hash.fmt("%s => %s", "\n") %]

Added missing HTML::Template::Expr vmethods
The following vmethods were added - they correspond to the perl functions of the same name.
```
    abs
    atan2
    cos
    exp
    hex
    lc
    log
    oct
    sin
    sprintf
    sqrt
    srand
    uc
    
```
Allow all Scalar vmethods to behave as top level functions.
```
    [% sprintf("%d %d", 7, 8) %] # = "7 8"
    
```
The following are equivalent in Alloy:
```
    [% "abc".length %]
    [% length("abc") %]
    
```
This feature may be disabling by setting the VMETHOD_FUNCTIONS configuration item to 0.

This is similar to how HTML::Template::Expr operates, but now you can use this functionality in TT templates as well.
Whitespace is less meaningful. (TT3)
```
    [% 2-1 %] # = 1 (fails in TT2)
    
```

Added pow operator.

    [% 2 ** 3 %] [% 2 pow 3 %] # = 8 8

Added string comparison operators (gt ge lt le cmp)

    [% IF "a" lt "b" %]a is less[% END %]

Added numeric comparison operator (<=>)
This can be used to make up for the fact that TT2 made == the same as eq (which will hopefully change - use eq when you mean eq).
```
    [% IF ! (a <=> b) %]a == b[% END %]

    [% IF (a <=> b) %]a != b[% END %]
    
```

Added self modifiers (+=, -=, *=, /=, %=, **=, ~=). (TT3)

    [% a = 2;  a *= 3  ; a %] # = 6
    [% a = 2; (a *= 3) ; a %] # = 66

Added pre and post increment and decrement (++ --). (TT3)

    [% ++a ; ++a %] # = 12
    [% a-- ; a-- %] # = 0-1

Added qw// contructor. (TT3)

    [% a = qw(a b c); a.1 %] # = b

    [% qw/a b c/.2 %] # = c

Added regex contructor. (TT3)

    [% "FOO".match(/(foo)/i).0 %] # = FOO

    [% a = /(foo)/i; "FOO".match(a).0 %] # = FOO

Allow for scientific notation. (TT3)

    [% a = 1.2e-20 %]

    [% 123.fmt('%.3e') %] # = 1.230e+02

Allow for hexadecimal input. (TT3)

    [% a = 0xff0000 %][% a %] # = 16711680

    [% a = 0xff2 / 0xd; a.fmt('%x') %] # = 13a

FOREACH variables can be nested.
```
    [% FOREACH f.b = [1..10] ; f.b ; END %]
    
```
Note that nested variables are subject to scoping issues. f.b will not be reset to its value before the FOREACH.

Post operative directives can be nested. (TT3)

Andy Wardley calls this side-by-side effect notation.

    [% one IF two IF three %]

    same as

    [% IF three %][% IF two %][% one %][% END %][% END %]


    [% a = [[1..3], [5..7]] %][% i FOREACH i = j FOREACH j = a %] # = 123567

Semi-colons on directives in the same tag are optional. (TT3)
```
    [% SET a = 1
       GET a
     %]

    [% FOREACH i = [1 .. 10]
         i
       END %]
    
```
Note: a semi-colon is still required in front of any block directive that can be used as a post-operative directive.
```
    [% 1 IF 0
       2 %]   # prints 2

    [% 1; IF 0
       2
       END %] # prints 1
    
```
Note2: This behavior can be disabled by setting the SEMICOLONS configuration item to a true value. If SEMICOLONS is true, then a SEMICOLON must be set after any directive that isn't followed by a post-operative directive.
CATCH blocks can be empty.
TT2 requires them to contain something.
Added a DUMP directive.
Used for Data::Dumper'ing the passed variable or expression.
```
   [% DUMP a.a %]
    
```

Added CONFIG directive.

   [% CONFIG
        ANYCASE   => 1
        PRE_CHOMP => '-'
   %]

Configuration options can use lowercase names instead of the all uppercase names that TT2 uses.

    my $t = Template::Alloy->new({
        anycase     => 1,
        interpolate => 1,
    });

Added LOOP directive (works the same as LOOP in HTML::Template.

   [%- var = [{key => 'a'}, {key => 'b'}] %]
   [%- LOOP var %]
     ([% key %])
   [%- END %]

   Prints

     (a)
     (b)

Alloy can parse HTML::Template and HTML::Template::Expr documents as well as TT2 and TT3 documents.
Added SYNTAX configuration. The SYNTAX configuration can be used to change what template syntax will be used for parsing included templates or eval'ed strings.
```
   [% CONFIG SYNTAX => 'hte' %]
   [% var = '<TMPL_VAR EXPR="sprintf('%s', 'hello world')">' %]
   [% var | eval %]
    
```
Added @() and $() and CALL_CONTEXT. Template::Toolkit uses a \concept that Alloy refers to as "smart" context. All function calls or method calls of variables in Template::Toolkit are made in list context. If one item is in the list, it is returned. If two or more items are returned - it returns an arrayref. This "does the right thing" most of the time - but can cause confusion in some cases and is difficult to work around without writing wrappers for the functions or methods in Perl.
Alloy has introduced the CALL_CONTEXT configuration item which defaults to "smart," but can also be set to "list" or "item." List context will always return an arrayref from called functions and methods and will call in list context. Item context will always call in item (scalar) context and will return one item.

The @() and $() operators allow for functions embedded inside to use list and item context (respectively). They are modeled after the corresponding Perl 6 context specifiers. See the Template::Alloy::Operators perldoc and CALL_CONTEXT configuration documentation for more information.
```
    [% array = @( this.get_rows ) %]

    [% item  = $( this.get_something ) %]
    
```

Added ->() MACRO operator.

The ->() operator behaves similarly to the MACRO directive, but can be used to pass functions to map, grep, and sort vmethods.

    [% MACRO foo(n) BLOCK %]Say [% n %][% END %]
    [% foo = ->(n){ "Say $n" } %]

    [% [0..10].grep(->(this % 2)).join %] prints 3 5 7 9
    [% ['a' .. 'c'].map(->(a){ a.upper }).join %] prints A B C
    [% [1,2,3].sort(->(a,b){ b <=> a }).join %] prints 3 2 1

The RETURN directive can take a variable or expression as a return value. Their are also "return" list, item, and hash vmethods. Return will also return from an enclosing MACRO.
```
    [% a = ->(n){ [1..n].return } %]
    
```
Alloy does not generate Perl code.
It generates an "opcode" tree. The opcode tree is an arrayref of scalars and array refs nested as deeply as possible. This "simple" structure could be shared TT implementations in other languages via JSON or YAML. You can optionally enable generating Perl code by setting COMPILE_PERL = 1.
Alloy uses storable for its compiled templates.
If EVAL_PERL is off, Alloy will not eval_string on ANY piece of information.
There is eval_filter and MACRO recursion protection
You can control the nested nature of eval_filter and MACRO recursion using the MAX_EVAL_RECURSE and MAX_MACRO_RECURSE configuration items.
There is no context.
Alloy provides a context object that mimics the Template::Context interface for use by some TT filters, eval perl blocks, views, and plugins.
There is no provider.
Alloy uses the load_template method to get and cache templates.
There is no parser/grammar.
Alloy has its own built-in recursive regex based parser and grammar system.

Alloy can actually be substituted in place of the native Template::Parser and Template::Grammar in TT by using the Template::Parser::Alloy module. This module uses the output of parse_tree to generate a TT style compiled perl document.
The DEBUG directive is more limited.
It only understands DEBUG_DIRS (8) and DEBUG_UNDEF (2).
Alloy has better line information
When debug dirs is on, directives on different lines separated by colons show the line they are on rather than a general line range.

Parse errors actually know what line and character they occurred at.

UNSUPPORTED TT2 CONFIGURATION

LOAD_TEMPLATES

Template::Alloy has its own mechanism for loading and storing compiled templates. TT would use a Template::Provider that would return a Template::Document. The closest thing in Template::Alloy is the load_template method. There is no immediate plan to support the TT behavior.

LOAD_PLUGINS

Template::Alloy uses its own mechanism for loading plugins. TT would use a Template::Plugins object to load plugins requested via the USE directive. The functionality for doing this in Template::Alloy is contained in the list_plugins method and the play_USE method. There is no immediate plan to support the TT behavior.

Full support is offered for the PLUGINS and LOAD_PERL configuration items.

Also note that Template::Alloy only has native support for the Iterator plugin. Any of the other plugins requested will need to provided by installing Template::Toolkit or the appropriate plugin module.

LOAD_FILTERS

Template::Alloy uses its own mechanism for loading filters. TT would use the Template::Filters object to load filters requested via the FILTER directive. The functionality for doing this in Template::Alloy is contained in the list_filters method and the play_expr method.

Full support is offered for the FILTERS configuration item.

TOLERANT

This option is used by the LOAD_TEMPLATES and LOAD_PLUGINS options and is not applicable in Template::Alloy.

SERVICE

Template::Alloy has no concept of service (theoretically the Template::Alloy is the "service").

CONTEXT

Template::Alloy provides its own pseudo context object to plugins, filters, and perl blocks. The Template::Alloy model doesn't really allow for a separate context. Template::Alloy IS the context.

PARSER

Template::Alloy has its own built in parser. The closest similarity is the parse_tree method. The output of parse_tree is an optree that is later run by execute_tree. Alloy provides a backend to the Template::Parser::Alloy module which can be used to replace the default parser when using the standard Template::Toolkit library.

GRAMMAR

Template::Alloy maintains its own grammar. The grammar is defined in the parse_tree method and the callbacks listed in the global $Template::Alloy::Parse::DIRECTIVES hashref.

AUTHOR

Paul Seamons <paul@seamons.com>

LICENSE

This module may be distributed under the same terms as Perl itself.