Brain.cs

using System;
using System.Diagnostics;
using System.IO;
namespace Brain
{
    class Program
    {
        public static void Main()
        {
            Console.Title = "BrainF Interpreter";
            start:;
            var programList = Directory.GetFiles("Programs\\");
            for (var i = 0; i < programList.Length; i++)
            {
                Console.WriteLine("[" + i + "] " + Path.GetFileNameWithoutExtension(programList[i]));
            }
            Console.Title = "BrainF Interpreter (WAITING FOR INPUT)";
            var input = Console.ReadLine();
            Console.Title = "BrainF Interpreter";
            var program = File.ReadAllText(programList[int.Parse(input)]).ToCharArray();

            var memory = new int[65536]; // 2^16 bytes of memory
            var pointer = 0;
            var memoryPointer = 0;
            var instructionCount = 0;
            var timing = Stopwatch.StartNew();
            while (pointer < program.Length)
            {
                var op = program[pointer];
                switch (op)
                {
                    case ('+'): memory[memoryPointer]++; break;
                    case ('-'): memory[memoryPointer]--; break;
                    case ('.'): Console.Write((char)memory[memoryPointer]); break;
                    case (','):
                        Console.Title = "BrainF Interpreter (WAITING FOR INPUT)";
                        memory[memoryPointer] = Console.ReadKey().KeyChar;
                        Console.Title = "BrainF Interpreter"; 
                        break;
                    case ('>'): memoryPointer++; break;
                    case ('<'): memoryPointer--; break;
                    case ('['):
                        if (memory[memoryPointer] == 0)
                        {
                            var depth = 1;
                            do
                            {
                                pointer++; 
                                depth = program[pointer] == ']' ? depth - 1 : 
                                    program[pointer] == '[' ? depth + 1 : depth;
                            } while (depth != 0);
                        }
                        break;
                    case (']'):
                        if (memory[memoryPointer] != 0)
                        {
                            var depth = -1;
                            do
                            {
                                pointer--; 
                                depth = program[pointer] == ']' ? depth - 1 : 
                                    program[pointer] == '[' ? depth + 1 : depth;
                            } while (depth != 0);
                        }
                        break;
                }
                pointer++;
                instructionCount++;
                if (memory[memoryPointer] < 0) { memory[memoryPointer] = 255; }
                if (memory[memoryPointer] > 255) { memory[memoryPointer] = 0; }
            }
            timing.Stop();

            Console.WriteLine("Program finished. Took " + timing.ElapsedMilliseconds + " ms. " + instructionCount + " instructions ran.");
            goto start;
        }
    }
}