Program      ::= Statement+

Statement    ::= (AssignmentStatement | FunctionCallStatement | IfStatement | WhileStatement | ReturnStatement) SEMICOLON

AssignmentStatement ::= "let" IDENTIFIER EQUALS Expression

FunctionCallStatement ::= IDENTIFIER LPAREN FunctionArguments? RPAREN

IfStatement ::= "if" Expression LBRACE Statement* RBRACE -- TODO: Should function definitions be allowed?

WhileStatement ::= "while" Expression LBRACE Statement* RBRACE

ReturnStatement ::= RETURN Expression

FunctionArguments ::= Expression ("," Expression)*

Expression   ::= EqualityExpression | AdditiveExpression | FunctionDefinition

EqualityExpression ::= AdditiveExpression "==" AdditiveExpression

AdditiveExpression ::= MultiplicativeExpression (("+" | "-") MultiplicativeExpression)*

MultiplicativeExpression ::= UnaryExpression (("*" | "/") UnaryExpression)*

UnaryExpression ::= ("!" | "-") UnaryExpression | PrimaryExpression

PrimaryExpression ::= NUMBER | BOOLEAN | IDENTIFIER | FunctionCallStatement | LPAREN Expression RPAREN

FunctionDefinition ::= LPAREN FunctionParameters? RPAREN ARROW LBRACE Statement* ReturnStatement SEMICOLON RBRACE

FunctionParameters ::= IDENTIFIER ("," IDENTIFIER)*