EBNF
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.. contents:: Table of Contents

Program
-------

The template language starts with the non-terminal token: "Program".

::

  Program             ::= Code EOF

  Code                ::= ( Text | Block )*

  Text                ::= TextBlock
                      |   LiteralBlock
                      |   DelimiterBlock


  Block               ::= CommentBlock 
                      |   DeclarationBlock
                      |   ModifyingBlock
                      |   OutputBlock
                      |   LiteralBlock
                      |   CycleBlock
                      |   LoopBlock
                      |   CodeFlowBlock

Text blocks
-----------
::

  TextBlock           ::= ( ~'{' | '\'! '{' )*

  LiteralBlock        ::= '{' 'literal' '}' Graphic* '{' '/literal' '}'

  DelimiterBlock      :==  '{ldelim}' | '{rdelim}'


Blocks
------
::

  CommentBlock        ::= '{*' Graphic* '*}'

  DeclarationBlock    ::= '{' 'var' SubDefineBlock '}'
                      |   '{' 'cycle' SubDefineBlock '}' 
                      |   '{' 'use' SubDefineBlock '}'

  SubDefineBlock      ::= PrimaryVariable ( '=' Expression )? ( ',' SubDefineBlock )?

  ModifyingBlock      ::= '{' SubAssignBlock (',' SubAssignBlock)* '}'

  SubAssignBlock      ::= AssignmentExpr | IncrementExpr | DecrementExpr

  AssignmentExpr      ::= PrimaryVariable ( '=' | CombinedAssignment) Expression

  IncrementExpr       ::= ( ( '++' PrimaryVariable ) | ( PrimaryVariable '++' ) )

  DecrementExpr       ::= ( ( '--' PrimaryVariable ) | ( PrimaryVariable '--' ) )

  OutputBlock         ::= '{' Expression '}'

  CycleBlock          ::= '{' 'increment' PrimaryVariable ( ',' PrimaryVariable )* '}'
                      |   '{' 'decrement' PrimaryVariable ( ',' PrimaryVariable )* '}'
                      |   '{' 'reset' PrimaryVariable ( ',' PrimaryVariable )* '}'


Loop control
------------
::

  LoopBlock           ::= ForeachStatement
                      |   WhileStatement

  ForeachStatement    ::= '{' 'foreach' Expression 'as' PrimaryVariable ('=>' PrimaryVariable)? (Cycle)* (OffsetAndLimit)? '}' Code '{' '/foreach' '}'

  WhileStatement      ::= '{' 'while' Expression '}' Code '{' '/while' '}'

  Cycle               ::= ('increment' | 'decrement') PrimaryVariable (',' PrimaryVariable)* 

  OffsetAndLimit      ::= ('offset' Expression)? ('limit' Expression)?


Code flow control
-----------------
::

  CodeFlowBlock       ::= IfStatement
                      |   SwitchStatement
                      |   IncludeStatement
                      |   DelimiterStatement
                      |   '{break}'
                      |   '{skip}'
                      |   '{continue}'
                      |   ReturnStatement


  IfStatement         ::= '{' 'if' Expression '}' Code (ElseIf)* (Else)? '{' '/if' '}' 
  ElseIf              ::= '{' 'elseif' Expression '}' Code
  Else                ::= '{' 'else' '}' Code 

  SwitchStatement     ::= '{' 'switch' Expression '}' (Case)* (DefaultCase)? '{' '/switch' '}'

  Case                ::= '{' 'case' Literal ( ',' Literal)* '}' Code '{' '/case' '}'

  DefaultCase         ::= '{' 'default' '}' Code '{' '/default' '}'
                     
  IncludeStatement    ::= '{' 'include' Expression ('send' ExprAsPrimVarList)? ('receive' PrimVarAsPrimVarList)? '}'

  DelimiterStatement  ::= '{' 'delimiter' (modulo Expression ('is' Expression)? )? '}' Code '{' '/delimiter' '}'

  ReturnStatement     ::= '{' 'return' ExprAsPrimVarList '}' 

  ExprAsPrimVarList   ::=  ( Expression 'as' PrimaryVariable | PrimaryVariable ) (',' ExprAsPrimVarList)?

  PrimVarAsPrimVarList::=  PrimaryVariable ('as' PrimaryVariable)? (',' PrimVarAsPrimVarList)?



Expression
----------
::

  Expression          ::= PreUnaryExpression (BinaryOperator Expression)?

  PreUnaryExpression  ::= '++' PrimaryVariable
                      |   '--' PrimaryVariable
                      |   UnaryExpression
                      |   Expression 'instanceof' Identifier 
                      |   ArrayDeclaration

  ArrayDeclaration    ::= 'array' '(' ( (Expression '=>')? Expression ( ',' Expression )* (',')? )? ')'
                      |   Expression '..' Expression


  UnaryExpression     ::= ( UnaryOperator )* PostFixExpression

  PostFixExpression   ::= PrimaryVariable ( '++' | '--' )?
                      |   Literal
                      |   FunctionCall
                      |   '(' Expression ')'


  PrimaryVariable     ::= '$' Identifier ( '[' Expression ']' | '->' Expression )*

  FunctionCall        ::= Identifier '(' (ParameterList)? ')'  
                                                                  
  ParameterList       ::= Expression ( ',' Expression )* 

  Identifier          ::= Letter ( Letter | Digit | '_' )*


Basic literals
--------------
::

  Literal              ::= NumeralLiteral 
                       |   StringLiteral 
                       |   BooleanLiteral
                       |   NullLiteral

  NumeralLiteral       ::=  HexLiteral | OctLiteral | FloatLiteral

  HexLiteral           ::= '0x' HexDigit+

  OctLiteral           ::= '0' OctDigit+

  FloatLiteral         ::= NonZeroDigit Digit* ( '.' Digit+ )? (('e'|'E') ('+'|'-')? Digit+)?

  StringLiteral        ::= '"' Graphic* '"' 
                       |   "'" Graphic* "'"

  BooleanLiteral       ::= 'true'
                       |   'false'

  NullLiteral          ::= 'null'


Lexicon
-------
::

  Comment             ::= '//' Graphic* ( EOL | '}' )
                      |   '/*' Graphic* '*/'

  Graphic             ::= Digit | Letter | Blank | Operators | Assignment | CombinedAssignment | RemainingCharSet

  EOL                 ::= end-of-line

  EOF                 ::= end-of-file

  Blank               ::= Tab | Space 

  NewLine             ::= '\n'

  Space               ::= ' '

  Tab                 ::= '\t'

  Letter              ::= 'a' ... 'z' | 'A' ... 'Z'  

  Hexdigit            ::= '0' .. '9' | 'A' .. 'F'

  Octdigit            ::= '0' .. '8'

  NonZeroDigit        ::= '1' .. '9' 

  Digit               ::= '0' | NonZeroDigit

  Assignment          ::= '='

  CombinedAssignment  ::= '+=' | '-='  | '*=' | '/=' | '%=' | '.=' 

  Operators           ::= BinaryOperator | UnaryOperator | '++' | '--'

  BinaryOperator      ::= ArithmeticOperator | ComparisonOperator | BooleanOperator | StringOperator

  ArithmeticOperator  ::= '+'  | '-'   | '*' | '/' | '%' 

  ComparisonOperator  ::= '==' | '===' | '!=' | '!==' | '<' | '<=' | '>' | '>=' 

  BooleanOperator     ::= '&&' | '||'

  StringOperator      ::= '.'  | '.='

  UnaryOperator       ::= '+'  | '-'   | '!'

  RemainingCharSet    ::= '.' | ':' | ';' | ',' | '~' | '(' | ')' | '[' | ']' | '{' | '}' | '_' | '|' | "'" | '"' | '`' | '#' | '$' | '@'






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