Pencil Grammar

<program> ::= <declaration>*;
<declaration> ::= <classDeclaration> | <funDeclaration> | <varDeclaration> | <statement>;
<classDeclaration> ::= "class" <identifier> ( ":" <identifier> )? "{" <function>* "}" ;
<funDeclaration> ::= "fun" <function>;
<varDeclaration> ::= "let" <identifier> ("=" <expression>)? ("," <identifier> \1?)* ";";
<function> ::= <identifier> "(" <parameters>? ")" <block>;
<statement> ::= <expressionStmt> | <block>| <ifThenStatement> | <whileStatement> | <forStatement>;
<ifThenStatement> ::= "if" "(" <expression> ")" <statement> ("else" <statement>)?;
<whileStatement> ::= "while" "(" <expression> ")" <statement>;
<forStatement> ::= "for" "(" (<varDeclaration> | <expressionStmt> | ";") <expression>? ";" <expression>? ")" <statement>;
<block> ::= "{" <declaration>* "}";
<expressionStmt> ::= <arguments> ";";
<arguments> ::= <expression> ("," <expression>)* ;
<expression> ::= <assignment>;
<assignment> ::= <identifier> ("=" | "+=" | "-=" | "*=" | "/=") <expression> | <trinary> | <logicalOr>;
<logicalOr> ::= <logicalAnd> ("or" <logicalAnd>)?;
<logicalAnd> ::= <trinary> ("and" <trinary>)?;
<trinary> ::= <equality> ("?" <trinary> ":" <trinary>)?;
<equality> ::= <comparision> (("==" | "!=") <comparision>)*;
<comparison> ::= <addition> ((">" | ">=" | "<" | "<=") <addition>)*;
<addition> ::= <multiplication> (("+" | "-") <multiplication>)*;
<multiplication> ::= <unary> (("+" | "-") <unary>)*;
<unary> ::= ("!" | "-" | "+" | "typeof" | "++" | "--") <unary> | <postfix>;
<postfix> ::= <call> ("++" | "--")?;
<call> ::= <literal> ("(" arguments? ")" | "." <identifier>)*;
<literal> ::= "(" <expression> ")" | <string> | <number> | "true" | "false" | "null" | <parameters>;
<parameters> ::= <identifier> ("," <identifier>)* ;
<identifier> ::= "@" \[A-z]\w\;
<number> ::= \\d\*;
<string> ::= (\[“’`]\) (\[^\1]\)* \1;