Jlox

Lox interpreter written in Java following the book Crafting Interpreters.

Branches:

main

If you are in the main branch you are looking at the implementation derived from the book.
It has some solved challenges and my own modifications.

Changes:

const - declaration for immutable data. Examples:

// Values
const x = 1;
x = 2; // Error at 'x': Cannot reassign a constant.

// Classes
class A {
    init(b) { this.b = 1; }
}

const a = A(1);
a.b = 2; // Error at 'b': Cannot modify a field of a constant object.

// But this is allowed:
var a_mut = a;
a.b = 2; // No error

break - statement for breaking out of loops. Example:

for (var i = 0; i < 10; i = i + 1) {
    if (i == 5) break;
    print i;
}

Output:
// 0
// 1
// 2
// 3
// 4

continue - statement for skipping the rest of the loop body. Example:

for (var i = 0; i < 10; i = i + 1) {
    if (i % 2 == 0) continue;
    print i;
}

Output:
// 1
// 3
// 5
// 7
// 9

Escape sequences in strings - [ \n, \r, \t, \b, \', \", \\ ]. Note " ' " still works, no need for " \' ". Examples:

// New line
print "Hello\nWorld"; // Hello
                      // World
                      // 

// Tab
print "Hello\tWorld"; // World  World

// Backspace
print "Hello\b World"; // Hell World

String and number concatenation using the '+' operator.

// string + number
print "123" + 4; // 1234 (string)

// number + string
print 4 + "123"; // 4123 (string)

def keyword before method declaration is now required.

// Before
class A {
    init() { print "A"; }
}

// Now
class A {
    def init() { print "A"; }
}

lambda expressions - anonymous functions. Examples:

// Single line
const add = lambda(a, b) { return a + b; };
print add(1, 2); // 3

// Multi line
const add = lambda(a, b) {
    var c = a + b;
    return c;
};
print add(3, 2); // 3

imports - importing other files. Examples:

// file1.lox
import "file2";  // Hello from file2
import "file3" as math;    

fun foo() {
    print "Hello from foo of file1";
}

foo();  // Hello from foo of file1
file2.foo();  // Hello from foo of file2

print math.pow(2, -math.PI);  // 0.0625

// file2.lox
fun foo() {
    print "Hello from foo of file2";
}

print "Hello from file2";

// file3.lox
fun pow(val, exp) {
    if (exp < 0) {
        return 1 / pow(val, -exp);
    }
    var result = 1;
    for (var i = 0; i < exp; i = i + 1) {
        result = result * val;
    }
    return result;
}

const PI = 3.14;

modulo operator. Examples:
```
print 4 % 2; // 0
print 5 % 2; // 1
```

jlox

If you are in the jlox branch you are looking at the implementation following the book.

Pawel-Parma/lox-java

Jlox

Branches:

main

jlox