The pbrain programming language is an extension I made to the Brainf**k programming language that adds the ability to define and call procedures. If you’re wondering about the asterisks in the name of the programming language, it’s because the name is rather rude. That’s why I decided to use a name for my extension that a good bit tamer. After all, my Mom and my kids still read my site from time to time.
After making a rather simplistic interpreter in C++, I decided to go ahead and make a .NET compiler as well, using C#.
Thanks to rdragon on the Undernet #c++ channel and to Daniel Cristofani for their comments and input.
A Nice IDE
There’s a nice integrated development environment written by Tim Rohlfs that includes support for pbrain. I was delighted when he added support. Go download it, try it out, and let him know how much you like it.
Some pbrain Programs
This is the pbrain program referred to in the comment header of the interpreter source.
1 2 3 4 5 | +([-]) +(-:<<[>>+<<-]>[>+<-]>) +([-]>++++++++++[<++++>-]<++++++++>[-]++:.) >+++>+++++>++: >+++: |
This pbrain program initializes a memory location to 65, the ASCII value of the letter ‘A’. It then calls a function for subsequent memory locations to copy the previous location and add one to it. Once a few cells are initialized, it prints all the cells to standard output.
1 2 3 4 5 6 7 8 | +([-]<[-]<[>+>+<<-]>>[<<+>>-]) +([-]>[-]+:<+) >>+++++++++++++[<+++++>-] ++: >++: >++: >++: <<<<.>.>.>.>. |
The .NET Compiler
Here is the C# source code for the .NET compiler, which compiles both pbrain and traditional Brainf**k code. It performs some simple optimizations as well:
- A sequence of
+and-instructions will be
concatenated into one operation sequence, so that a sequence like
++++will add 4 to the current memory location instead of
adding 1 four times. - Likewise, a sequence of
>and<
instructions will be concatenated into one operation sequence, so that
a sequence like>>>>will move the pointer forward four
locations rather than 1 location at a time. - The null loop,
[-], will be compiled to set the
current memory location to zero, since that is the practical effect of
the loop anyway. This will allow for efficiently zeroing out a memory
location whether it holds the value 1 or 10001.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 | using System; using System.Collections; using System.IO; using System.Reflection; using System.Reflection.Emit; using System.Text; using System.Threading; namespace ParksComputing.Pbrain { /// <summary> /// Compiler implements the pbrain compiler. /// </summary> class Compiler { /// <summary> /// The main entry point for the application. /// </summary> static void Main(string[] args) { if (args.Length > 0) { String fileName = args[0]; Compiler compiler; compiler = new Compiler(fileName); Type myType = compiler.Compile(); } } private String fileName; private String asmName; private String asmFileName; private AssemblyBuilder myAsmBldr; private FieldBuilder mem; private FieldBuilder mp; private FieldBuilder tmp; private FieldBuilder vtbl; private TypeBuilder myTypeBldr; private MethodInfo readMI; private MethodInfo writeMI; private MethodInfo hashAddMI; private MethodInfo hashGetMI; private int methodCount; private int callCount; void Ldc(ILGenerator il, int count) { switch (count) { case 0: il.Emit(OpCodes.Ldc_I4_0); break; case 1: il.Emit(OpCodes.Ldc_I4_1); break; case 2: il.Emit(OpCodes.Ldc_I4_2); break; case 3: il.Emit(OpCodes.Ldc_I4_3); break; case 4: il.Emit(OpCodes.Ldc_I4_4); break; case 5: il.Emit(OpCodes.Ldc_I4_5); break; case 6: il.Emit(OpCodes.Ldc_I4_6); break; case 7: il.Emit(OpCodes.Ldc_I4_7); break; case 8: il.Emit(OpCodes.Ldc_I4_8); break; default: il.Emit(OpCodes.Ldc_I4, count); break; } } void Forward(ILGenerator il, int count) { //ldsfld int32 pbout.mp il.Emit(OpCodes.Ldsfld, mp); //ldc.i4 1 Ldc(il, count); //add il.Emit(OpCodes.Add); //stsfld int32 pbout.mp il.Emit(OpCodes.Stsfld, mp); } void Back(ILGenerator il, int count) { //ldsfld int32 pbout.mp il.Emit(OpCodes.Ldsfld, mp); //ldc.i4 1 Ldc(il, count); //sub il.Emit(OpCodes.Sub); //stsfld int32 pbout.mp il.Emit(OpCodes.Stsfld, mp); } void Plus(ILGenerator il, int count) { //ldsfld int32[] pbout.mem il.Emit(OpCodes.Ldsfld, mem); //ldsfld int32 pbout.mp il.Emit(OpCodes.Ldsfld, mp); //ldelem.i4 il.Emit(OpCodes.Ldelem_I4); //ldc.i4 1 Ldc(il, count); //add il.Emit(OpCodes.Add); //stsfld int32 pbout.tmp il.Emit(OpCodes.Stsfld, tmp); //ldsfld int32[] pbout.mem il.Emit(OpCodes.Ldsfld, mem); //ldsfld int32 pbout.mp il.Emit(OpCodes.Ldsfld, mp); //ldsfld int32 pbout.tmp il.Emit(OpCodes.Ldsfld, tmp); //stelem.i4 il.Emit(OpCodes.Stelem_I4); } void Minus(ILGenerator il, int count) { //ldsfld int32[] pbout.mem il.Emit(OpCodes.Ldsfld, mem); //ldsfld int32 pbout.mp il.Emit(OpCodes.Ldsfld, mp); //ldelem.i4 il.Emit(OpCodes.Ldelem_I4); //ldc.i4 1 Ldc(il, count); //sub il.Emit(OpCodes.Sub); //stsfld int32 pbout.tmp il.Emit(OpCodes.Stsfld, tmp); //ldsfld int32[] pbout.mem il.Emit(OpCodes.Ldsfld, mem); //ldsfld int32 pbout.mp il.Emit(OpCodes.Ldsfld, mp); //ldsfld int32 pbout.tmp il.Emit(OpCodes.Ldsfld, tmp); //stelem.i4 il.Emit(OpCodes.Stelem_I4); } void Read(ILGenerator il) { //ldsfld int32[] pbout.mem il.Emit(OpCodes.Ldsfld, mem); //ldsfld int32 pbout.mp il.Emit(OpCodes.Ldsfld, mp); //call void [mscorlib]System.Console.Write(char) il.EmitCall(OpCodes.Call, readMI, null); //stelem.i4 il.Emit(OpCodes.Stelem_I4); } void Write(ILGenerator il) { //ldsfld int32[] pbout.mem il.Emit(OpCodes.Ldsfld, mem); //ldsfld int32 pbout.mp il.Emit(OpCodes.Ldsfld, mp); //ldelem.i4 il.Emit(OpCodes.Ldelem_I4); //call void [mscorlib]System.Console.Write(char) il.EmitCall(OpCodes.Call, writeMI, null); } void LoopBegin(ILGenerator il, Label endLabel) { //ldsfld int32[] pbout.mem il.Emit(OpCodes.Ldsfld, mem); //ldsfld int32 pbout.mp il.Emit(OpCodes.Ldsfld, mp); //ldelem.i4 il.Emit(OpCodes.Ldelem_I4); //brfalse loop_1_end il.Emit(OpCodes.Brfalse, endLabel); } void LoopEnd(ILGenerator il, Label beginLabel) { //br loop_1_start il.Emit(OpCodes.Br, beginLabel); } void Call(ILGenerator il) { //ldsfld object pbout.vtbl il.Emit(OpCodes.Ldsfld, vtbl); //ldsfld int32[] pbout.mem il.Emit(OpCodes.Ldsfld, mem); //ldsfld int32 pbout.mp il.Emit(OpCodes.Ldsfld, mp); //ldelem.i4 il.Emit(OpCodes.Ldelem_I4); //box int32 il.Emit(OpCodes.Box, typeof(int)); //call instance object [mscorlib]System.Collections.Hashtable.get_Item(object) il.EmitCall(OpCodes.Call, hashGetMI, null); //calli void() il.EmitCalli(OpCodes.Calli, System.Runtime.InteropServices.CallingConvention.StdCall, null, null); } void Zero(ILGenerator il) { //ldsfld int32[] pbout.mem il.Emit(OpCodes.Ldsfld, mem); //ldsfld int32 pbout.mp il.Emit(OpCodes.Ldsfld, mp); //ldc.i4.0 il.Emit(OpCodes.Ldc_I4_0); //stelem.i4 il.Emit(OpCodes.Stelem_I4); } Type Compile() { // .field private static int32 mp mp = myTypeBldr.DefineField("mp", typeof(int), FieldAttributes.Private | FieldAttributes.Static); // .field private static int32[] mem mem = myTypeBldr.DefineField("mem", typeof(Array), FieldAttributes.Private | FieldAttributes.Static); // .field private static int32 tmp tmp = myTypeBldr.DefineField("tmp", typeof(int), FieldAttributes.Private | FieldAttributes.Static); // .method private static int32 main() cil managed MethodBuilder mainBldr = myTypeBldr.DefineMethod( "main", (MethodAttributes)(MethodAttributes.Private | MethodAttributes.Static), typeof(int), null ); ILGenerator il = mainBldr.GetILGenerator(); // ldc.i4 30000 il.Emit(OpCodes.Ldc_I4, 30000); // newarr [mscorlib]System.Int32 il.Emit(OpCodes.Newarr, typeof(int)); // stsfld int32[] pbout.mem il.Emit(OpCodes.Stsfld, mem); // ldc.i4 0 il.Emit(OpCodes.Ldc_I4_0); // stsfld int32 pbout.mp il.Emit(OpCodes.Stsfld, mp); Parse(il); // ldsfld int32[] pbout.mem il.Emit(OpCodes.Ldsfld, mem); // ldsfld int32 pbout.mp il.Emit(OpCodes.Ldsfld, mp); // ldelem.i4 il.Emit(OpCodes.Ldelem_I4); // ret il.Emit(OpCodes.Ret); Type pboutType = myTypeBldr.CreateType(); myAsmBldr.SetEntryPoint(mainBldr); myAsmBldr.Save(asmFileName); Console.WriteLine("Assembly saved as '{0}'.", asmFileName); return pboutType; } void Parse(ILGenerator il) { using (FileStream fs = File.OpenRead(fileName)) { char c; int n; Queue q = new Queue(); while ((n = fs.ReadByte()) != -1) { c = (char)n; q.Enqueue(c); if (c == ':') { ++callCount; } } if (callCount > 0) { // .field private static object vtbl vtbl = myTypeBldr.DefineField("vtbl", typeof(Object), FieldAttributes.Private | FieldAttributes.Static); //newobj instance void [mscorlib]System.Collections.Hashtable..ctor() Type hashtableType = typeof(System.Collections.Hashtable); ConstructorInfo constructorInfo = hashtableType.GetConstructor( (BindingFlags.Instance | BindingFlags.Public), null, CallingConventions.HasThis, System.Type.EmptyTypes, null ); il.Emit(OpCodes.Newobj, constructorInfo); //stsfld object pbout.vtbl il.Emit(OpCodes.Stsfld, vtbl); } Interpret(q, il); } } MethodBuilder Procedure(Queue q) { Type[] temp0 = { myTypeBldr }; StringBuilder sb = new StringBuilder(); sb.Append("pb_"); sb.Append(methodCount); String name = sb.ToString(); MethodBuilder procBldr = myTypeBldr.DefineMethod( name, (MethodAttributes.Private | MethodAttributes.Static), null, System.Type.EmptyTypes ); ILGenerator il = procBldr.GetILGenerator(); Interpret(q, il); // ret il.Emit(OpCodes.Ret); return procBldr; } int CountDuplicates(Queue q, char c) { int count = 1; char inst = c; while (c == inst && q.Count > 0) { c = (char)q.Peek(); if (c == inst) { c = (char)q.Dequeue(); ++count; } } return count; } void Interpret(Queue q, ILGenerator il) { System.Collections.IEnumerator myEnumerator = q.GetEnumerator(); char c; byte b; while (q.Count > 0) { c = (char)q.Dequeue(); switch (c) { case '+': Plus(il, CountDuplicates(q, c)); break; case '-': Minus(il, CountDuplicates(q, c)); break; case '>': Forward(il, CountDuplicates(q, c)); break; case '<': Back(il, CountDuplicates(q, c)); break; case ',': Read(il); break; case '.': Write(il); break; case '[': { if (q.Count > 0) { Queue lq = new Queue(); int nest = 0; int startPos = q.Count; bool pair = false; bool zero = false; bool opt = true; // Find the matching ] while (q.Count > 0) { c = (char)q.Dequeue(); if (c == '[') { ++nest; } else if (c == ']') { if (nest > 0) { --nest; } else { pair = true; break; } } // Check for null loop, [-], which set the current cell // to zero. There's no need to loop. Just store a zero // and move on. else if (opt && c == '-' && (startPos - q.Count) == 1) { opt = false; // If the next character is the end of the loop... if ((char)q.Peek() == ']') { // Eat the ] and stop the loop c = (char)q.Dequeue(); zero = true; break; } } lq.Enqueue(c); } if (zero) { Zero(il); break; } // If no matching ] is found in source block, report error. if (q.Count != 0 && !pair) { // throw System.Exception(); } Label beginLabel = il.DefineLabel(); Label endLabel = il.DefineLabel(); il.MarkLabel(beginLabel); LoopBegin(il, endLabel); Interpret(lq, il); LoopEnd(il, beginLabel); il.MarkLabel(endLabel); } } break; case '(': { // LoopBegin(il, endLabel); if (q.Count > 0) { bool pair = false; Queue lq = new Queue(); int nest = 0; // Find the matching ) while (q.Count > 0) { c = (char)q.Dequeue(); if (c == '(') { ++nest; } else if (c == ')') { if (nest > 0) { --nest; } else { pair = true; break; } } lq.Enqueue(c); } // If no matching ) is found in source block, report error. if (q.Count != 0 && !pair) { // throw 5; } MethodBuilder procBldr = Procedure(lq); //ldsfld object pbout.vtbl il.Emit(OpCodes.Ldsfld, vtbl); //ldsfld int32[] pbout.mem il.Emit(OpCodes.Ldsfld, mem); //ldsfld int32 pbout.mp il.Emit(OpCodes.Ldsfld, mp); //ldelem.i4 il.Emit(OpCodes.Ldelem_I4); //box int32 il.Emit(OpCodes.Box, typeof(int)); //ldftn void pbout.pb_0() il.Emit(OpCodes.Ldftn, procBldr); //call instance void [mscorlib]System.Collections.Hashtable.Add(object,object) il.EmitCall(OpCodes.Call, hashAddMI, null); } ++methodCount; } break; case ':': Call(il); break; default: break; } } } Compiler(String fileNameInit) { fileName = fileNameInit; methodCount = 0; callCount = 0; asmName = Path.GetFileNameWithoutExtension(fileName); asmFileName = Path.GetFileName(Path.ChangeExtension(fileName, ".exe")); AssemblyName myAsmName = new AssemblyName(); myAsmName.Name = asmName; myAsmBldr = Thread.GetDomain().DefineDynamicAssembly(myAsmName, AssemblyBuilderAccess.RunAndSave); Type[] temp1 = { typeof(Char) }; writeMI = typeof(Console).GetMethod("Write", temp1); readMI = typeof(Console).GetMethod("Read"); Type[] temp2 = { typeof(Object), typeof(Object) }; hashAddMI = typeof(System.Collections.Hashtable).GetMethod("Add", temp2); Type[] temp3 = { typeof(Object) }; hashGetMI = typeof(System.Collections.Hashtable).GetMethod("get_Item", temp3); // .class private auto ansi pbout extends [mscorlib]System.Object ModuleBuilder myModuleBldr = myAsmBldr.DefineDynamicModule(asmFileName, asmFileName); myTypeBldr = myModuleBldr.DefineType(asmName); } }; } |
The Interpreter
Here is the C++ source code for the interpreter. If you want to compile it with g++ make sure you get version 3.4 or later so it won’t choke on the wchar_t bits.
I don’t claim that this is a particularly efficient interpreter. I thought of it, designed it, and wrote it one evening/morning between the hours of 9:45 PM and 6:15 AM, in a single session.
This interpreter will also work with traditional Brainf**k code.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 | /* Interpreter for the pbrain programming language (procedural Brainf**k) Copyright(C) Paul M. Parks All Rights Reserved. v1.4.3 2004/07/15 12:10 paul@parkscomputing.com https://www.parkscomputing.com/ The syntax is the same as traditional Brainf**k, with the following symbols added: ( Begin procedure ) End procecure : Call procedure identified by the value at the current location Procedures are identified by numeric ID: +([-]) Assuming the current location is zero, defines a procedure number 1 that sets the current location to zero when called. ++(<<[>>+<<-]>[>+<-]>) Assuming the current location is zero, defines a procedure number 2 that accepts two parameters. It adds parameter 1 and parameter 2 and places the result in the location that was current when the procedure was called, zeroing out parameters 1 and 2 in the process. +++([-]>++++++++++[<++++>-]<++++++++>[-]++:.) Assuming the current location is zero, defines a procedure 3 that prints the ASCII equivalent of the numeral at the current location, between 0 and 9. +++>+++++>++: Calls procedure 2, passing in parameters 3 and 5. All of the above examples may be combined into the program below. Note that the procedures are numbered 1, 2, and 3 because the current location is incremented prior to each procedure definition. +([-]) +(-:<<[>>+<<-]>[>+<-]>) +([-]>++++++++++[<++++>-]<++++++++>[-]++:.) >+++>+++++>++: >+++: An error condition is reported with a short diagnostic to stderr and an error number returned from the executable. Errors reported by the interpreter are as follows: 1 - Out of memory 2 - Unknown procedure 3 - Memory address out of range 4 - Cannot find matching ] for beginning [ 999 - Unknown exception */ #include <vector> #include <iostream> #include <fstream> #include <iterator> #include <map> #if defined(_MSC_VER) #pragma warning(disable: 4571) #endif // Define the type contained in the memory array #ifndef PBRAIN_MEM_TYPE #define PBRAIN_MEM_TYPE int #endif // Define the character input/output type. #ifndef PBRAIN_CHARACTER_TYPE #define PBRAIN_CHARACTER_TYPE wchar_t #endif // Set the initial size of the memory array, if not defined externally. #ifndef PBRAIN_INIT_MEM_SIZE #define PBRAIN_INIT_MEM_SIZE 30000 #endif // By default, use a dynamic array to store memory locations. #ifndef PBRAIN_STATIC_MEMORY typedef std::vector<pbrain_mem_type> Mem; Mem mem(PBRAIN_INIT_MEM_SIZE); Mem::size_type mp = 0; #else PBRAIN_MEM_TYPE mem[PBRAIN_INIT_MEM_SIZE]; size_t mp = 0; #endif // Placeholder template class to be specialized below. template<typename Ch> struct io_types {}; // Define appropriate I/O and stream iterator types for working with byte // characters. template<> struct io_types<char> { static std::istream& cin; static std::ostream& cout; typedef std::basic_ifstream<char, std::char_traits<char> > ifstream; typedef std::istream_iterator<char, char> istream_iterator; }; std::istream& io_types<char>::cin = std::cin; std::ostream& io_types<char>::cout = std::cout; // Define appropriate I/O and stream iterator types for working with wide // characters. template<> struct io_types<wchar_t> { static std::wistream& cin; static std::wostream& cout; typedef std::basic_ifstream<wchar_t, std::char_traits<wchar_t> > ifstream; typedef std::istream_iterator<wchar_t, wchar_t> istream_iterator; }; std::wistream& io_types<wchar_t>::cin = std::wcin; std::wostream& io_types<wchar_t>::cout = std::wcout; // Useful type that chooses the appropriate typedefs for the character width typedef io_types<pbrain_character_type> io; // Type for storing a string of instructions; used for procedures and loops typedef std::vector<pbrain_character_type> SourceBlock; // Type for storing procedures indexed by number typedef std::map<pbrain_mem_type, std::vector<PBRAIN_CHARACTER_TYPE> > Procedures; // Map of procedure IDs to procedures Procedures procedures; // Interpret a container of instructions template<typename It> void interpret(It ii, It eos) { while (ii != eos) { switch (*ii) { case '+': ++mem[mp]; break; case '-': --mem[mp]; break; case '>': ++mp; #ifndef PBRAIN_STATIC_MEMORY // If memory is kept in a dynamic array, the array will grow as // needed. try { if (mp == mem.size()) { mem.resize(mem.size() * 2); } } catch (...) { // Ostensibly an out-of-memory condition. throw 1; } #else // Static memory cannot grow, so throw when limit reached if (mp == sizeof(mem) / sizeof(PBRAIN_MEM_TYPE)) { throw 1; } #endif break; case '<': --mp; // Throw out-of-range error if cell location is decremented below 0 if (static_cast<int>(mp) < 0) { throw 3; } break; case '.': io::cout.put(static_cast<PBRAIN_CHARACTER_TYPE>(mem[mp])); break; case ',': mem[mp] = static_cast<pbrain_mem_type>(io::cin.get()); break; case '[': // Move to first instruction in the loop ++ii; { int nest = 0; It begin = ii; // Find the matching ] while (ii != eos) { if (*ii == '[') { ++nest; } else if (*ii == ']') { if (nest) { --nest; } else { break; } } ++ii; } // If no matching ] is found in source block, report error. if (ii == eos) { throw 4; } // At this point the iterator will point at the matching ] // character, which is one instruction past the end of the range // of instructions to be processed in a loop. loop(begin, ii); } break; case '(': ++ii; { SourceBlock sourceBlock; while (ii != eos && *ii != ')') { sourceBlock.push_back(*ii); ++ii; } procedures.insert(std::make_pair(mem[mp], sourceBlock)); } break; case ':': { // Look up the source block that matches the value at the current // location. If found, execute it. Procedures::iterator i = procedures.find(mem[mp]); if (i != procedures.end()) { interpret(i->second.begin(), i->second.end()); } else { throw 2; } } break; default: break; } ++ii; } } template<typename It> void loop(It ii, It eos) { // Interpret instructions until the value in the current memory location // is zero while (mem[mp]) { interpret(ii, eos); } } template<typename C> void parse(C& c) { io::istream_iterator ii(c); io::istream_iterator eos; SourceBlock sourceBlock; // Copy instructions from the input stream to a source block. while (ii != eos) { sourceBlock.push_back(*ii); ++ii; } // Execute the instructions in the source block interpret(sourceBlock.begin(), sourceBlock.end()); } int main(int argc, char** argv) try { // Read from a file if a filename is provided as an argument. if (argc > 1) { io::ifstream source(argv[1]); if (source.is_open()) { parse(source); } } // Otherwise interpret code from stdin else { parse(io::cin); } } catch (int e) { std::cerr << "Error " << e << ", cell " << unsigned int(mp) << "\n"; exit(e); } catch (...) { std::cerr << "Error " << 999 << ", cell " << unsigned int(mp) << "\n"; exit(999); } |
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