Provided by: libtemplate-alloy-perl_1.016-1_all bug

NAME

       Template::Alloy::Operator - Operator role.

DESCRIPTION

       The Template::Alloy::Operator role provides the regexes necessary for
       Template::Alloy::Parse to parse operators and place them in their appropriate precedence.
       It also provides the play_operator method which is used by Template::Alloy::Play and
       Template::Alloy::Compile for playing out the stored operator ASTs.

ROLE METHODS

       play_operator
           Takes an operator AST in the form of

               [undef, '+', 1, 2]

           Essentially, all operators are stored in RPN notation with a leading "undef" to
           disabiguate operators in a normal Alloy expression AST.

       define_operator
           Used for defining new operators.

           See Template::Alloy for more details.

OPERATOR LIST

       The following operators are available in Template::Alloy.  Except where noted these are
       the same operators available in TT.  They are listed in the order of their precedence (the
       higher the precedence the tighter it binds).

       "." The dot operator.  Allows for accessing sub-members, methods, or virtual methods of
           nested data structures.

               my $obj->process(\$content, {a => {b => [0, {c => [34, 57]}]}}, \$output);

               [% a.b.1.c.0 %] => 34

           Note: on access to hashrefs, any hash keys that match the sub key name will be used
           before a virtual method of the same name.  For example if a passed hash contained pair
           with a keyname "defined" and a value of "2", then any calls to
           hash.defined(another_keyname) would always return 2 rather than using the vmethod
           named "defined."  To get around this limitation use the "|" operator (listed next).
           Also - on objects the "." will always try and call the method by that name.  To always
           call the vmethod - use "|".

       "|" The pipe operator.  Similar to the dot operator.  Allows for explicit calling of
           virtual methods and filters (filters are "merged" with virtual methods in
           Template::Alloy and TT3) when accessing hashrefs and objects.  See the note for the
           "." operator.

           The pipe character is similar to TT2 in that it can be used in place of a directive as
           an alias for FILTER.  It similar to TT3 in that it can be used for virtual method
           access.  This duality is one source of difference between Template::Alloy and TT2
           compatibility.  Templates that have directives that end with a variable name that then
           use the "|" directive to apply a filter will be broken as the "|" will be applied to
           the variable name.

           The following two cases will do the same thing.

               [% foo | html %]

               [% foo FILTER html %]

           Though they do the same thing, internally, foo|html is stored as a single variable
           while "foo FILTER html" is stored as the variable foo which is then passed to the
           FILTER html.

           A TT2 sample that would break in Template::Alloy or TT3 is:

               [% PROCESS foo a = b | html %]

           Under TT2 the content returned by "PROCESS foo a = b" would all be passed to the html
           filter.  Under Template::Alloy and TT3, b would be passed to the html filter before
           assigning it to the variable "a" before the template foo was processed.

           A simple fix is to do any of the following:

               [% PROCESS foo a = b FILTER html %]

               [% | html %][% PROCESS foo a = b %][% END %]

               [% FILTER html %][% PROCESS foo a = b %][% END %]

           This shouldn't be too much hardship and offers the great return of disambiguating
           virtual method access.

       "\" Unary.  The reference operator.  Not well publicized in TT.  Stores a reference to a
           variable for use later.  Can also be used to "alias" long names.

               [% f = 7 ; foo = \f ; f = 8 ; foo %] => 8

               [% foo = \f.g.h.i.j.k; f.g.h.i.j.k = 7; foo %] => 7

               [% f = "abcd"; foo = \f.replace("ab", "-AB-") ; foo %] => -AB-cd

               [% f = "abcd"; foo = \f.replace("bc") ; foo("-BC-") %] => a-BC-d


               [% f = "abcd"; foo = \f.replace ; foo("cd", "-CD-") %] => ab-CD-
       "++ --"
           Pre and post increment and decrement.  My be used as either a prefix or postfix
           operator.

               [% ++a %][% ++a %] => 12

               [% a++ %][% a++ %] => 01

               [% --a %][% --a %] => -1-2

               [% a-- %][% a-- %] => 0-1

       "**  ^  pow"
           Right associative binary.  X raised to the Y power.  This isn't available in TT 2.15.

               [% 2 ** 3 %] => 8

       "!" Prefix not.  Negation of the value.

       "-" Prefix minus.  Returns the value multiplied by -1.

               [% a = 1 ; b = -a ; b %] => -1

       "*" Left associative binary. Multiplication.

       "/  div  DIV"
           Left associative binary. Division.  Note that / is floating point division, but div
           and DIV are integer division.

              [% 10  /  4 %] => 2.5
              [% 10 div 4 %] => 2

       "%  mod  MOD"
           Left associative binary. Modulus.

              [% 15 % 8 %] => 7

       "+" Left associative binary.  Addition.

       "-" Left associative binary.  Minus.

       "_  ~"
           Left associative binary.  String concatenation.

               [% "a" ~ "b" %] => ab

       "<  >  <=  >="
           Non associative binary.  Numerical comparators.

       "lt  gt  le  ge"
           Non associative binary.  String comparators.

       "eq"
           Non associative binary.  String equality test.

       "=="
           Non associative binary. In TT syntaxes the V2EQUALS configuration item defaults to
           true which means this operator will operate the same as the "eq" operator.  Setting
           V2EQUALS to 0 will change this operator to mean numeric equality.  You could also use
           [% ! (a <=> b) %] but that is a bit messy.

           The HTML::Template syntaxes default V2EQUALS to 0 which means that it will test for
           numeric equality just as you would normally expect.

           In either case - you should always use "eq" when you mean "eq".  The V2EQUALS will
           most likely eventually default to 0.

       "ne"
           Non associative binary.  String non-equality test.

       "!="
           Non associative binary. In TT syntaxes the V2EQUALS configuration item defaults to
           true which means this operator will operate the same as the "ne" operator.  Setting
           V2EQUALS to 0 will change this operator to mean numeric non-equality.  You could also
           use [% (a <=> b) %] but that is a bit messy.

           The HTML::Template syntaxes default V2EQUALS to 0 which means that it will test for
           numeric non-equality just as you would normally expect.

           In either case - you should always use "ne" when you mean "ne".  The V2EQUALS will
           most likely eventually default to 0.

       "<=>"
           Non associative binary.  Numeric comparison operator.  Returns -1 if the first
           argument is less than the second, 0 if they are equal, and 1 if the first argument is
           greater.

       "cmp"
           Non associative binary.  String comparison operator.  Returns -1 if the first argument
           is less than the second, 0 if they are equal, and 1 if the first argument is greater.

       "&&"
           Left associative binary.  And.  All values must be true.  If all values are true, the
           last value is returned as the truth value.

               [% 2 && 3 && 4 %] => 4

       "||"
           Right associative binary.  Or.  The first true value is returned.

               [% 0 || '' || 7 %] => 7

           Note: perl is left associative on this operator - but it doesn't matter because || has
           its own precedence level.  Setting it to right allows for Alloy to short circuit
           earlier in the expression optree (left is (((1,2), 3), 4) while right is (1, (2, (3,
           4))).

       "//"
           Right associative binary.  Perl 6 err.  The first defined value is returned.

               [% foo // bar %]

       ".."
           Non associative binary.  Range creator.  Returns an arrayref containing the values
           between and including the first and last arguments.

               [% t = [1 .. 5] %] => variable t contains an array with 1,2,3,4, and 5

           It is possible to place multiple ranges in the same [] constructor.  This is not
           available in TT.

               [% t = [1..3, 6..8] %] => variable t contains an array with 1,2,3,6,7,8

           The .. operator is the only operator that returns a list of items.

       "? :"
           Ternary - right associative.  Can be nested with other ?: pairs.

               [% 1 ? 2 : 3 %] => 2
               [% 0 ? 2 : 3 %] => 3

       "*= += -= /= **= %= ~="
           Self-modifying assignment - right associative.  Sets the left hand side to the
           operation of the left hand side and right (clear as mud).  In order to not conflict
           with SET, FOREACH and other operations, this operator is only available in
           parenthesis.

              [% a = 2 %][%  a += 3  %] --- [% a %]    => --- 5   # is handled by SET
              [% a = 2 %][% (a += 3) %] --- [% a %]    => 5 --- 5

       "=" Assignment - right associative.  Sets the left-hand side to the value of the righthand
           side.  In order to not conflict with SET, FOREACH and other operations, this operator
           is only available in parenthesis.  Returns the value of the righthand side.

              [%  a = 1  %] --- [% a %]    => --- 1   # is handled by SET
              [% (a = 1) %] --- [% a %]    => 1 --- 1

       "not  NOT"
           Prefix. Lower precedence version of the '!' operator.

       "and  AND"
           Left associative. Lower precedence version of the '&&' operator.

       "or OR"
           Right associative. Lower precedence version of the '||' operator.

       "err ERR"
           Right associative.  Lower precedence version of the '//' operator.

       "->" (Not in TT2)
           Macro operator.  Works like the MACRO directive but can be used in map, sort, and grep
           list operations.  Syntax is based on the Perl 6 pointy sub.  There are two diffences
           from the MACRO directive.  First is that if no argument list is specified, a default
           argument list with a single parameter named "this" will be used.  Second, the "->"
           operator parses its block as if it was already in a template tag.

               [% foo = ->{ "Hi" } %][% foo %] => Hi
               [% foo = ->{ this.repeat(2) } %][% foo("Hi") %] => HiHi
               [% foo = ->(n){ n.repeat(2) } %][% foo("Hi") %] => HiHi
               [% foo = ->(a,b){ a; "|"; b } %][% foo(2,3) %]  => 2|3

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

               [% [1,2,3].sort(->(a,b){ b <=> a }).join %] prints 3 2 1

               [% c = [{k => "wow"}, {k => "wee"}, {k => "a"}] %]
               [% c.sort(->(a,b){ a.k cmp b.k }).map(->{this.k}).join %] => a wee wow

           Note: Care should be used when attempting to sort large lists.  The mini-language of
           Template::Alloy is a interpreted language running in Perl which is an interpreted
           language.  There are likely to be performance issues when trying to do low level
           functions such as sort on large lists.

           The RETURN directive and return item, list, and hash vmethods can be used to return
           more interesting values from a MACRO.

             [% a = ->(n){ [1..n].return } %]
             [% a(3).join %]    => 1 2 3
             [% a(10).join %]   => 1 2 3 4 5 6 7 8 9 10

           The Schwartzian transform is now possible in Template::Alloy (somebody somewhere is
           rolling over in their grave).

             [%- qw(Z a b D y M)
                   .map(->{ [this.lc, this].return })
                   .sort(->(a,b){a.0 cmp b.0})
                   .map(->{this.1})
                   .join %]          => a b D M y Z

       "{}"
           This operator is not exposed for external use.  It is used internally by
           Template::Alloy to delay the creation of a hash until the execution of the compiled
           template.

       "[]"
           This operator is not exposed for external use.  It is used internally by
           Template::Alloy to delay the creation of an array until the execution of the compiled
           template.

       "@()"
           List context specifier.  Methods or functions inside this operator will always be
           called in list context and will always return an arrayref of the results.  See the
           CALL_CONTEXT configuration directive.

       "$()"
           Item context specifier.  Methods or functions inside this operator will always be
           called in item (scalar) context.  See the CALL_CONTEXT configuration directive.

       "qr"
           This operator is not exposed for external use.  It is used internally by
           Template::Alloy to store a regular expression and its options.  It will return a
           compiled Regexp object when compiled.

       "-temp-"
           This operator is not exposed for external use.  It is used internally by some
           directives to pass temporary, literal data into play_expr to allow additional vmethods
           or filters to be called on existing data.

AUTHOR

       Paul Seamons <paul at seamons dot com>

LICENSE

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