Colin Cross | 7bb052a | 2015-02-03 12:59:37 -0800 | [diff] [blame] | 1 | // run |
| 2 | |
| 3 | // Copyright 2009 The Go Authors. All rights reserved. |
| 4 | // Use of this source code is governed by a BSD-style |
| 5 | // license that can be found in the LICENSE file. |
| 6 | |
| 7 | // Test simulating a Turing machine, sort of. |
| 8 | |
| 9 | package main |
| 10 | |
| 11 | // brainfuck |
| 12 | |
| 13 | var p, pc int |
| 14 | var a [30000]byte |
| 15 | |
| 16 | const prog = "++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.+++++++..+++.>++.<<+++++++++++++++.>.+++.------.--------.>+.>.!" |
| 17 | |
| 18 | func scan(dir int) { |
| 19 | for nest := dir; dir*nest > 0; pc += dir { |
| 20 | switch prog[pc+dir] { |
| 21 | case ']': |
| 22 | nest-- |
| 23 | case '[': |
| 24 | nest++ |
| 25 | } |
| 26 | } |
| 27 | } |
| 28 | |
| 29 | func main() { |
| 30 | r := "" |
| 31 | for { |
| 32 | switch prog[pc] { |
| 33 | case '>': |
| 34 | p++ |
| 35 | case '<': |
| 36 | p-- |
| 37 | case '+': |
| 38 | a[p]++ |
| 39 | case '-': |
| 40 | a[p]-- |
| 41 | case '.': |
| 42 | r += string(a[p]) |
| 43 | case '[': |
| 44 | if a[p] == 0 { |
| 45 | scan(1) |
| 46 | } |
| 47 | case ']': |
| 48 | if a[p] != 0 { |
| 49 | scan(-1) |
| 50 | } |
| 51 | default: |
| 52 | if r != "Hello World!\n" { |
| 53 | panic(r) |
| 54 | } |
| 55 | return |
| 56 | } |
| 57 | pc++ |
| 58 | } |
| 59 | } |