Complete grammar of the Jack language

• This grammar specification is based on the following conventions:
• ‘xxx’ : Quoted boldface is used for tokens that appear verbatim (“terminals”);
• xxx : Regular typeface is used for names of language constructs (“non-terminals”);
• ( ) : Parentheses are used for grouping of language constructs;
• x | y : Indicates that either x or y can appear;
• x? : Indicates that x appears 0 or 1 times;
• x* : Indicates that x appears 0 or more times.

Lexical elements

Lexical elements	The Jack language includes five types of terminal elements (tokens):
keyword	‘class’ | ‘constructor’ | ‘function’ | ‘method’ | ‘field’ | ‘static’ | ‘var’ | ‘int’ | ‘char’ | ‘boolean’ | ‘void’ | ‘true’ | ‘false’ | ‘null’ | ‘this’ | ‘let’ | ‘do’ | ‘if’ | ‘else’ | ‘while’ | ‘return’
symbol	‘{’ | ‘}’ | ‘(’ | ‘)’ | ‘[’ | ‘]’ | ‘.’ | ‘;’ | ‘;’ | ‘+’ | ‘-’ | ‘*’ | ‘/’ | ‘&’ | ‘|’ | ‘<’ | ‘>’ | ‘=’ | ‘~’
integerConstant	A decimal number in the range 0 .. 32767.
stringConstant	‘"’ A sequence of Unicode characters not including double quote or newline. ‘"’
identifier	A sequence of letters, digits, and underscore (‘_’) not starting with a digit.

Program structure

Program structure	A Jack program is a collection of classes, each appearing in a separate file. The compilation unit is a class. A class is a sequence of tokens structured according to the following context free syntax:
class	‘class’ className ‘{’ classVarDec* subroutineDec* ‘}’
classVarDec:	(‘static’ | ‘field’) type varName (‘,’ varName)* ‘;’
type	‘int’ | ‘char’ | ‘boolean’ | className
subroutineDec	(‘constructor’ | ‘function’ | ‘method’) (‘void’ | type) subroutineName ‘(’ parameterList ‘)’ subroutineBody
parameterList	((type varName) (‘,’ type varName)*)?
subroutineBody	‘{’ varDec* statements ‘}’
varDec	‘var’ type varName (‘;’ varName)* ‘;’
className	identifier
subroutineName	identifier
varName	identifier

Statements

Statements
statements:	statement*
statement:	letStatement | ifStatement | whileStatement | doStatement | returnStatement
letStatement:	‘let’ varName (‘[’ expression ‘]’)? ‘=’ expression ‘;’
ifStatement:	‘if’ ‘(’ expression ‘)’ ‘{’ statements ‘}’ (‘else’ ‘{’ statements ‘}’)?
whileStatement:	‘while’ ‘(’ expression ‘)’ ‘{’ statements ‘}’
doStatement:	‘do’ subroutineCall ‘;’
ReturnStatement:	‘return’ expression? ‘;’

Expressions

Expressions:
expression:	term (op term)*
term:	intergerConstant | stringConstant | keywordConstant | varName | varName ‘[’ expression ‘]’ | subroutineCall | ‘(’ expression ‘)’ | unaryOp term
subroutineCall:	subroutineName ‘(’ expressionList ‘)’ | (className | varName) ‘.’ subroutineName ‘(’ expressionList ‘)’
expressionList:	(expression (‘,’ expression)* )?
op:	‘+’ | ‘-’ | ‘*’ | ‘/’ | ‘&’ | ‘|’ | ‘<’ | ‘>’ | ‘=’
unaryOp:	‘-’ | ‘~’
KeywordConstant:	‘true’ | ‘false’ | ‘null’ | ‘this’