Program      ::= Statement+

Statement    ::= (AssignmentStatement | ImportDeclaration | ExternDeclaration | CastStatement | SizeOfStatement | FunctionCallStatement | IfStatement | WhileStatement | ReturnStatement | "break" | "continue") SEMICOLON

AssignmentStatement ::= ("let")? ("*")? Expression EQUALS Expression

ImportDeclaration ::= "import" STRING

ExternDeclaration ::= "extern" IDENTIFIER EQUALS Type

FunctionCallStatement ::= (IDENTIFIER | FunctionDefinition) 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

CastStatement ::= "cast" LPAREN TYPE "," Expression RPAREN
    
SizeOfStatement ::= "sizeof" LPAREN TYPE RPAREN

EqualityExpression ::= AdditiveExpression ("==" | "!=" | "<=" | ">=" | "<" | ">") AdditiveExpression

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

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

UnaryExpression ::= ("!" | "-" | "*") UnaryExpression | PostfixExpression

PostfixExpression ::= PrimaryExpression (FieldAccess | FunctionCallStatement | CastStatement | SizeOfStatement)*

PrimaryExpression ::= NULL | NUMBER | BOOLEAN | CHAR | STRING | IDENTIFIER | FunctionDefinition | StructDefinition | StructInstantiation | FieldAccess | LPAREN Expression RPAREN

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

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

Type ::= IDENTIFIER | FunctionType

FunctionType ::= LPAREN (Type ("," Type)*)? RPAREN ARROW Type

ParameterTypes ::= Type ("," Type)*

StructDefinition ::= "struct" LBRACE (StructField ("," StructField)*)? RBRACE

StructField ::= IDENTIFIER ":" Type

StructInstantiation ::= IDENTIFIER LBRACE RBRACE

FieldAccess ::= Expression DOT IDENTIFIER