// run | |
// Copyright 2009 The Go Authors. All rights reserved. | |
// Use of this source code is governed by a BSD-style | |
// license that can be found in the LICENSE file. | |
// Test simulating a Turing machine, sort of. | |
package main | |
// brainfuck | |
var p, pc int | |
var a [30000]byte | |
const prog = "++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.+++++++..+++.>++.<<+++++++++++++++.>.+++.------.--------.>+.>.!" | |
func scan(dir int) { | |
for nest := dir; dir*nest > 0; pc += dir { | |
switch prog[pc+dir] { | |
case ']': | |
nest-- | |
case '[': | |
nest++ | |
} | |
} | |
} | |
func main() { | |
r := "" | |
for { | |
switch prog[pc] { | |
case '>': | |
p++ | |
case '<': | |
p-- | |
case '+': | |
a[p]++ | |
case '-': | |
a[p]-- | |
case '.': | |
r += string(a[p]) | |
case '[': | |
if a[p] == 0 { | |
scan(1) | |
} | |
case ']': | |
if a[p] != 0 { | |
scan(-1) | |
} | |
default: | |
if r != "Hello World!\n" { | |
panic(r) | |
} | |
return | |
} | |
pc++ | |
} | |
} |