masaxsuzu / monkey

A Toy Programming Language

Writing an interpreter/compiler in Go

This is an implementation of the Monkey from Thorsten Ball's books

• Writing An interpreter In Go.
• Writing A Compiler In Go.

monkey > let hello = monkey
let hello = monkey;

Syntax

As of now, these syntaxes are available.

• literal

  • integer: "1" -> 1
  • true: "true" -> true
  • false: "false" -> false
  • function: "fn(x) {return x}" -> fn(x) return x;

• statement

  • let: "let x = 1" -> let x = 1;
  • return: "return x" -> return x;

• expression

  • if: "if(x) {return x}" -> if x return x;
  • if-else: "if(x) {return x} else{return 0}" -> if x return x; else return 0;
  • call: "add(1,2)" -> add(1, 2)

• operator

  • "!": "!x" -> (!x)
  • "+": "x + y" -> (x + y)
  • "-": "x - y" -> (x - y)
  • "*": "x * y" -> (x * y)
  • "/": "x / y" -> (x / y)
  • "==": "x == y" -> (x == y)
  • "!=": "x != y" -> (x != y)
  • ">": "x > y" -> (x > y)
  • "<": "x < y" -> (x < y)

Examples

• Let statement

let x = 200;
let y = 100;
x + y; // -> 300

• Return statement

return 200;
let x = 100;
3 * x; // -> 200

• If-else expression

if(1 > 0) {
    return 100;
} else {
    return 200;
} // -> 100

• Function literal & calling function

let f = fn(x) {
    return x * 100;
};
f(10); // -> 1000

• Closure

let f = fn(x){
    let z = 3 * x;
    return fn(y){
        z + y;
    }
};
f(1)(2); // -> 5

• Recursive function

let fib = fn(x){
    if(x < 2) {
        return x;
    }
    return fib(x-1) + fib(x-2);
};
fib(6); // -> 8

monkey's Issues

Panic when running "return 1;" on virtual machine

VM実行において、Function文以外でreturn命令を実行するとPanicが発生する。

~/go/src/github.com/masa-suzu/monkey
$ go run main.go -vm
Hello! This is the Monkey programming language!
>> return 1;
panic: runtime error: index out of range

goroutine 1 [running]:
github.com/masa-suzu/monkey/vm.(*VirtualMachine).push(0xc0001be080, 0x515f00, 0xc00005e120, 0x0, 0x0)
        C:/Users/szk11/go/src/github.com/masa-suzu/monkey/vm/vm.go:260 +0xdf
github.com/masa-suzu/monkey/vm.(*VirtualMachine).Run(0xc0001be080, 0xc0000a4000, 0x10000)
        C:/Users/szk11/go/src/github.com/masa-suzu/monkey/vm/vm.go:188 +0xbde
github.com/masa-suzu/monkey/repl.Rep_VM(0xc00005e104, 0x9, 0x515600, 0xc000086008, 0xc00005e100, 0x5da6b8, 0x0, 0x0, 0xc0000a4000, 0x10000, ...)
        C:/Users/szk11/go/src/github.com/masa-suzu/monkey/repl/repl.go:87 +0x22e
github.com/masa-suzu/monkey/repl.Start(0x5155e0, 0xc000086000, 0x515600, 0xc000086008, 0x4fad30, 0x3, 0x1)
        C:/Users/szk11/go/src/github.com/masa-suzu/monkey/repl/repl.go:33 +0x458
main.main()
        C:/Users/szk11/go/src/github.com/masa-suzu/monkey/main.go:21 +0xbc
exit status 2

インタプリタ実行では発生しない。

~/go/src/github.com/masa-suzu/monkey
$ go run main.go
Hello! This is the Monkey programming language!
>> return 1;
1