jlox

Lox

 // Your first Lox program!
 print "Hello, world!";

• Dynamic typing
• Automatic memory management
• Data Types
  • Booleans
  • Numbers
  • Strings
  • Nil
• Expressions
  • Arithmetic
  • Comparison and equality
  • Logical operators
  • Precedence and grouping
• Statements
• Variables
• Control Flow
• Functions
• Closures
• Classes

A Grammar for Lox expressions

• Literals. Numbers,strings,Booleans, and nil
• Unary expressions. A prefix ! to perform a logical not, and - to negate a number.
• Binary expressions. The infix arithmetic(+,-,*,/) and logic operators (==, !=, <, <=,>,>=)

• Parentheses. A pair of ( and ) wrapped around and expression.

  • Syntax tree

    expression     → literal
    | unary
    | binary
    | grouping ;
      
    literal        → NUMBER | STRING | "true" | "false" | "nil" ;
    grouping       → "(" expression ")" ;
    unary          → ( "-" | "!" ) expression ;
    binary         → expression operator expression ;
    operator       → "==" | "!=" | "<" | "<=" | ">" | ">="
    | "+"  | "-"  | "*" | "/" ;
      
  

Name	Operators	Associates
Equality	== !=	Left
Comparison	> >= < <=	Left
Term	- +	Left
Factor	/ *	Left
Unary	! -	Right

expression     → equality ;
equality       → comparison ( ( "!=" | "==" ) comparison )* ;
comparison     → term ( ( ">" | ">=" | "<" | "<=" ) term )* ;
term           → factor ( ( "-" | "+" ) factor )* ;
factor         → unary ( ( "/" | "*" ) unary )* ;
unary          → ( "!" | "-" ) unary
               | primary ;
primary        → NUMBER | STRING | "true" | "false" | "nil"
               | "(" expression ")" ;