1 ============================================================ 2 Kaleidoscope: Extending the Language: User-defined Operators 3 ============================================================ 4 5 .. contents:: 6 :local: 7 8 Chapter 6 Introduction 9 ====================== 10 11 Welcome to Chapter 6 of the "`Implementing a language with 12 LLVM <index.html>`_" tutorial. At this point in our tutorial, we now 13 have a fully functional language that is fairly minimal, but also 14 useful. There is still one big problem with it, however. Our language 15 doesn't have many useful operators (like division, logical negation, or 16 even any comparisons besides less-than). 17 18 This chapter of the tutorial takes a wild digression into adding 19 user-defined operators to the simple and beautiful Kaleidoscope 20 language. This digression now gives us a simple and ugly language in 21 some ways, but also a powerful one at the same time. One of the great 22 things about creating your own language is that you get to decide what 23 is good or bad. In this tutorial we'll assume that it is okay to use 24 this as a way to show some interesting parsing techniques. 25 26 At the end of this tutorial, we'll run through an example Kaleidoscope 27 application that `renders the Mandelbrot set <#kicking-the-tires>`_. This gives an 28 example of what you can build with Kaleidoscope and its feature set. 29 30 User-defined Operators: the Idea 31 ================================ 32 33 The "operator overloading" that we will add to Kaleidoscope is more 34 general than in languages like C++. In C++, you are only allowed to 35 redefine existing operators: you can't programmatically change the 36 grammar, introduce new operators, change precedence levels, etc. In this 37 chapter, we will add this capability to Kaleidoscope, which will let the 38 user round out the set of operators that are supported. 39 40 The point of going into user-defined operators in a tutorial like this 41 is to show the power and flexibility of using a hand-written parser. 42 Thus far, the parser we have been implementing uses recursive descent 43 for most parts of the grammar and operator precedence parsing for the 44 expressions. See `Chapter 2 <LangImpl02.html>`_ for details. By 45 using operator precedence parsing, it is very easy to allow 46 the programmer to introduce new operators into the grammar: the grammar 47 is dynamically extensible as the JIT runs. 48 49 The two specific features we'll add are programmable unary operators 50 (right now, Kaleidoscope has no unary operators at all) as well as 51 binary operators. An example of this is: 52 53 :: 54 55 # Logical unary not. 56 def unary!(v) 57 if v then 58 0 59 else 60 1; 61 62 # Define > with the same precedence as <. 63 def binary> 10 (LHS RHS) 64 RHS < LHS; 65 66 # Binary "logical or", (note that it does not "short circuit") 67 def binary| 5 (LHS RHS) 68 if LHS then 69 1 70 else if RHS then 71 1 72 else 73 0; 74 75 # Define = with slightly lower precedence than relationals. 76 def binary= 9 (LHS RHS) 77 !(LHS < RHS | LHS > RHS); 78 79 Many languages aspire to being able to implement their standard runtime 80 library in the language itself. In Kaleidoscope, we can implement 81 significant parts of the language in the library! 82 83 We will break down implementation of these features into two parts: 84 implementing support for user-defined binary operators and adding unary 85 operators. 86 87 User-defined Binary Operators 88 ============================= 89 90 Adding support for user-defined binary operators is pretty simple with 91 our current framework. We'll first add support for the unary/binary 92 keywords: 93 94 .. code-block:: c++ 95 96 enum Token { 97 ... 98 // operators 99 tok_binary = -11, 100 tok_unary = -12 101 }; 102 ... 103 static int gettok() { 104 ... 105 if (IdentifierStr == "for") 106 return tok_for; 107 if (IdentifierStr == "in") 108 return tok_in; 109 if (IdentifierStr == "binary") 110 return tok_binary; 111 if (IdentifierStr == "unary") 112 return tok_unary; 113 return tok_identifier; 114 115 This just adds lexer support for the unary and binary keywords, like we 116 did in `previous chapters <LangImpl5.html#lexer-extensions-for-if-then-else>`_. One nice thing 117 about our current AST, is that we represent binary operators with full 118 generalisation by using their ASCII code as the opcode. For our extended 119 operators, we'll use this same representation, so we don't need any new 120 AST or parser support. 121 122 On the other hand, we have to be able to represent the definitions of 123 these new operators, in the "def binary\| 5" part of the function 124 definition. In our grammar so far, the "name" for the function 125 definition is parsed as the "prototype" production and into the 126 ``PrototypeAST`` AST node. To represent our new user-defined operators 127 as prototypes, we have to extend the ``PrototypeAST`` AST node like 128 this: 129 130 .. code-block:: c++ 131 132 /// PrototypeAST - This class represents the "prototype" for a function, 133 /// which captures its argument names as well as if it is an operator. 134 class PrototypeAST { 135 std::string Name; 136 std::vector<std::string> Args; 137 bool IsOperator; 138 unsigned Precedence; // Precedence if a binary op. 139 140 public: 141 PrototypeAST(const std::string &name, std::vector<std::string> Args, 142 bool IsOperator = false, unsigned Prec = 0) 143 : Name(name), Args(std::move(Args)), IsOperator(IsOperator), 144 Precedence(Prec) {} 145 146 Function *codegen(); 147 const std::string &getName() const { return Name; } 148 149 bool isUnaryOp() const { return IsOperator && Args.size() == 1; } 150 bool isBinaryOp() const { return IsOperator && Args.size() == 2; } 151 152 char getOperatorName() const { 153 assert(isUnaryOp() || isBinaryOp()); 154 return Name[Name.size() - 1]; 155 } 156 157 unsigned getBinaryPrecedence() const { return Precedence; } 158 }; 159 160 Basically, in addition to knowing a name for the prototype, we now keep 161 track of whether it was an operator, and if it was, what precedence 162 level the operator is at. The precedence is only used for binary 163 operators (as you'll see below, it just doesn't apply for unary 164 operators). Now that we have a way to represent the prototype for a 165 user-defined operator, we need to parse it: 166 167 .. code-block:: c++ 168 169 /// prototype 170 /// ::= id '(' id* ')' 171 /// ::= binary LETTER number? (id, id) 172 static std::unique_ptr<PrototypeAST> ParsePrototype() { 173 std::string FnName; 174 175 unsigned Kind = 0; // 0 = identifier, 1 = unary, 2 = binary. 176 unsigned BinaryPrecedence = 30; 177 178 switch (CurTok) { 179 default: 180 return LogErrorP("Expected function name in prototype"); 181 case tok_identifier: 182 FnName = IdentifierStr; 183 Kind = 0; 184 getNextToken(); 185 break; 186 case tok_binary: 187 getNextToken(); 188 if (!isascii(CurTok)) 189 return LogErrorP("Expected binary operator"); 190 FnName = "binary"; 191 FnName += (char)CurTok; 192 Kind = 2; 193 getNextToken(); 194 195 // Read the precedence if present. 196 if (CurTok == tok_number) { 197 if (NumVal < 1 || NumVal > 100) 198 return LogErrorP("Invalid precedence: must be 1..100"); 199 BinaryPrecedence = (unsigned)NumVal; 200 getNextToken(); 201 } 202 break; 203 } 204 205 if (CurTok != '(') 206 return LogErrorP("Expected '(' in prototype"); 207 208 std::vector<std::string> ArgNames; 209 while (getNextToken() == tok_identifier) 210 ArgNames.push_back(IdentifierStr); 211 if (CurTok != ')') 212 return LogErrorP("Expected ')' in prototype"); 213 214 // success. 215 getNextToken(); // eat ')'. 216 217 // Verify right number of names for operator. 218 if (Kind && ArgNames.size() != Kind) 219 return LogErrorP("Invalid number of operands for operator"); 220 221 return llvm::make_unique<PrototypeAST>(FnName, std::move(ArgNames), Kind != 0, 222 BinaryPrecedence); 223 } 224 225 This is all fairly straightforward parsing code, and we have already 226 seen a lot of similar code in the past. One interesting part about the 227 code above is the couple lines that set up ``FnName`` for binary 228 operators. This builds names like "binary@" for a newly defined "@" 229 operator. It then takes advantage of the fact that symbol names in the 230 LLVM symbol table are allowed to have any character in them, including 231 embedded nul characters. 232 233 The next interesting thing to add, is codegen support for these binary 234 operators. Given our current structure, this is a simple addition of a 235 default case for our existing binary operator node: 236 237 .. code-block:: c++ 238 239 Value *BinaryExprAST::codegen() { 240 Value *L = LHS->codegen(); 241 Value *R = RHS->codegen(); 242 if (!L || !R) 243 return nullptr; 244 245 switch (Op) { 246 case '+': 247 return Builder.CreateFAdd(L, R, "addtmp"); 248 case '-': 249 return Builder.CreateFSub(L, R, "subtmp"); 250 case '*': 251 return Builder.CreateFMul(L, R, "multmp"); 252 case '<': 253 L = Builder.CreateFCmpULT(L, R, "cmptmp"); 254 // Convert bool 0/1 to double 0.0 or 1.0 255 return Builder.CreateUIToFP(L, Type::getDoubleTy(TheContext), 256 "booltmp"); 257 default: 258 break; 259 } 260 261 // If it wasn't a builtin binary operator, it must be a user defined one. Emit 262 // a call to it. 263 Function *F = getFunction(std::string("binary") + Op); 264 assert(F && "binary operator not found!"); 265 266 Value *Ops[2] = { L, R }; 267 return Builder.CreateCall(F, Ops, "binop"); 268 } 269 270 As you can see above, the new code is actually really simple. It just 271 does a lookup for the appropriate operator in the symbol table and 272 generates a function call to it. Since user-defined operators are just 273 built as normal functions (because the "prototype" boils down to a 274 function with the right name) everything falls into place. 275 276 The final piece of code we are missing, is a bit of top-level magic: 277 278 .. code-block:: c++ 279 280 Function *FunctionAST::codegen() { 281 // Transfer ownership of the prototype to the FunctionProtos map, but keep a 282 // reference to it for use below. 283 auto &P = *Proto; 284 FunctionProtos[Proto->getName()] = std::move(Proto); 285 Function *TheFunction = getFunction(P.getName()); 286 if (!TheFunction) 287 return nullptr; 288 289 // If this is an operator, install it. 290 if (P.isBinaryOp()) 291 BinopPrecedence[P.getOperatorName()] = P.getBinaryPrecedence(); 292 293 // Create a new basic block to start insertion into. 294 BasicBlock *BB = BasicBlock::Create(TheContext, "entry", TheFunction); 295 ... 296 297 Basically, before codegening a function, if it is a user-defined 298 operator, we register it in the precedence table. This allows the binary 299 operator parsing logic we already have in place to handle it. Since we 300 are working on a fully-general operator precedence parser, this is all 301 we need to do to "extend the grammar". 302 303 Now we have useful user-defined binary operators. This builds a lot on 304 the previous framework we built for other operators. Adding unary 305 operators is a bit more challenging, because we don't have any framework 306 for it yet - let's see what it takes. 307 308 User-defined Unary Operators 309 ============================ 310 311 Since we don't currently support unary operators in the Kaleidoscope 312 language, we'll need to add everything to support them. Above, we added 313 simple support for the 'unary' keyword to the lexer. In addition to 314 that, we need an AST node: 315 316 .. code-block:: c++ 317 318 /// UnaryExprAST - Expression class for a unary operator. 319 class UnaryExprAST : public ExprAST { 320 char Opcode; 321 std::unique_ptr<ExprAST> Operand; 322 323 public: 324 UnaryExprAST(char Opcode, std::unique_ptr<ExprAST> Operand) 325 : Opcode(Opcode), Operand(std::move(Operand)) {} 326 327 Value *codegen() override; 328 }; 329 330 This AST node is very simple and obvious by now. It directly mirrors the 331 binary operator AST node, except that it only has one child. With this, 332 we need to add the parsing logic. Parsing a unary operator is pretty 333 simple: we'll add a new function to do it: 334 335 .. code-block:: c++ 336 337 /// unary 338 /// ::= primary 339 /// ::= '!' unary 340 static std::unique_ptr<ExprAST> ParseUnary() { 341 // If the current token is not an operator, it must be a primary expr. 342 if (!isascii(CurTok) || CurTok == '(' || CurTok == ',') 343 return ParsePrimary(); 344 345 // If this is a unary operator, read it. 346 int Opc = CurTok; 347 getNextToken(); 348 if (auto Operand = ParseUnary()) 349 return llvm::make_unique<UnaryExprAST>(Opc, std::move(Operand)); 350 return nullptr; 351 } 352 353 The grammar we add is pretty straightforward here. If we see a unary 354 operator when parsing a primary operator, we eat the operator as a 355 prefix and parse the remaining piece as another unary operator. This 356 allows us to handle multiple unary operators (e.g. "!!x"). Note that 357 unary operators can't have ambiguous parses like binary operators can, 358 so there is no need for precedence information. 359 360 The problem with this function, is that we need to call ParseUnary from 361 somewhere. To do this, we change previous callers of ParsePrimary to 362 call ParseUnary instead: 363 364 .. code-block:: c++ 365 366 /// binoprhs 367 /// ::= ('+' unary)* 368 static std::unique_ptr<ExprAST> ParseBinOpRHS(int ExprPrec, 369 std::unique_ptr<ExprAST> LHS) { 370 ... 371 // Parse the unary expression after the binary operator. 372 auto RHS = ParseUnary(); 373 if (!RHS) 374 return nullptr; 375 ... 376 } 377 /// expression 378 /// ::= unary binoprhs 379 /// 380 static std::unique_ptr<ExprAST> ParseExpression() { 381 auto LHS = ParseUnary(); 382 if (!LHS) 383 return nullptr; 384 385 return ParseBinOpRHS(0, std::move(LHS)); 386 } 387 388 With these two simple changes, we are now able to parse unary operators 389 and build the AST for them. Next up, we need to add parser support for 390 prototypes, to parse the unary operator prototype. We extend the binary 391 operator code above with: 392 393 .. code-block:: c++ 394 395 /// prototype 396 /// ::= id '(' id* ')' 397 /// ::= binary LETTER number? (id, id) 398 /// ::= unary LETTER (id) 399 static std::unique_ptr<PrototypeAST> ParsePrototype() { 400 std::string FnName; 401 402 unsigned Kind = 0; // 0 = identifier, 1 = unary, 2 = binary. 403 unsigned BinaryPrecedence = 30; 404 405 switch (CurTok) { 406 default: 407 return LogErrorP("Expected function name in prototype"); 408 case tok_identifier: 409 FnName = IdentifierStr; 410 Kind = 0; 411 getNextToken(); 412 break; 413 case tok_unary: 414 getNextToken(); 415 if (!isascii(CurTok)) 416 return LogErrorP("Expected unary operator"); 417 FnName = "unary"; 418 FnName += (char)CurTok; 419 Kind = 1; 420 getNextToken(); 421 break; 422 case tok_binary: 423 ... 424 425 As with binary operators, we name unary operators with a name that 426 includes the operator character. This assists us at code generation 427 time. Speaking of, the final piece we need to add is codegen support for 428 unary operators. It looks like this: 429 430 .. code-block:: c++ 431 432 Value *UnaryExprAST::codegen() { 433 Value *OperandV = Operand->codegen(); 434 if (!OperandV) 435 return nullptr; 436 437 Function *F = getFunction(std::string("unary") + Opcode); 438 if (!F) 439 return LogErrorV("Unknown unary operator"); 440 441 return Builder.CreateCall(F, OperandV, "unop"); 442 } 443 444 This code is similar to, but simpler than, the code for binary 445 operators. It is simpler primarily because it doesn't need to handle any 446 predefined operators. 447 448 Kicking the Tires 449 ================= 450 451 It is somewhat hard to believe, but with a few simple extensions we've 452 covered in the last chapters, we have grown a real-ish language. With 453 this, we can do a lot of interesting things, including I/O, math, and a 454 bunch of other things. For example, we can now add a nice sequencing 455 operator (printd is defined to print out the specified value and a 456 newline): 457 458 :: 459 460 ready> extern printd(x); 461 Read extern: 462 declare double @printd(double) 463 464 ready> def binary : 1 (x y) 0; # Low-precedence operator that ignores operands. 465 ... 466 ready> printd(123) : printd(456) : printd(789); 467 123.000000 468 456.000000 469 789.000000 470 Evaluated to 0.000000 471 472 We can also define a bunch of other "primitive" operations, such as: 473 474 :: 475 476 # Logical unary not. 477 def unary!(v) 478 if v then 479 0 480 else 481 1; 482 483 # Unary negate. 484 def unary-(v) 485 0-v; 486 487 # Define > with the same precedence as <. 488 def binary> 10 (LHS RHS) 489 RHS < LHS; 490 491 # Binary logical or, which does not short circuit. 492 def binary| 5 (LHS RHS) 493 if LHS then 494 1 495 else if RHS then 496 1 497 else 498 0; 499 500 # Binary logical and, which does not short circuit. 501 def binary& 6 (LHS RHS) 502 if !LHS then 503 0 504 else 505 !!RHS; 506 507 # Define = with slightly lower precedence than relationals. 508 def binary = 9 (LHS RHS) 509 !(LHS < RHS | LHS > RHS); 510 511 # Define ':' for sequencing: as a low-precedence operator that ignores operands 512 # and just returns the RHS. 513 def binary : 1 (x y) y; 514 515 Given the previous if/then/else support, we can also define interesting 516 functions for I/O. For example, the following prints out a character 517 whose "density" reflects the value passed in: the lower the value, the 518 denser the character: 519 520 :: 521 522 ready> extern putchard(char); 523 ... 524 ready> def printdensity(d) 525 if d > 8 then 526 putchard(32) # ' ' 527 else if d > 4 then 528 putchard(46) # '.' 529 else if d > 2 then 530 putchard(43) # '+' 531 else 532 putchard(42); # '*' 533 ... 534 ready> printdensity(1): printdensity(2): printdensity(3): 535 printdensity(4): printdensity(5): printdensity(9): 536 putchard(10); 537 **++. 538 Evaluated to 0.000000 539 540 Based on these simple primitive operations, we can start to define more 541 interesting things. For example, here's a little function that determines 542 the number of iterations it takes for a certain function in the complex 543 plane to diverge: 544 545 :: 546 547 # Determine whether the specific location diverges. 548 # Solve for z = z^2 + c in the complex plane. 549 def mandelconverger(real imag iters creal cimag) 550 if iters > 255 | (real*real + imag*imag > 4) then 551 iters 552 else 553 mandelconverger(real*real - imag*imag + creal, 554 2*real*imag + cimag, 555 iters+1, creal, cimag); 556 557 # Return the number of iterations required for the iteration to escape 558 def mandelconverge(real imag) 559 mandelconverger(real, imag, 0, real, imag); 560 561 This "``z = z2 + c``" function is a beautiful little creature that is 562 the basis for computation of the `Mandelbrot 563 Set <http://en.wikipedia.org/wiki/Mandelbrot_set>`_. Our 564 ``mandelconverge`` function returns the number of iterations that it 565 takes for a complex orbit to escape, saturating to 255. This is not a 566 very useful function by itself, but if you plot its value over a 567 two-dimensional plane, you can see the Mandelbrot set. Given that we are 568 limited to using putchard here, our amazing graphical output is limited, 569 but we can whip together something using the density plotter above: 570 571 :: 572 573 # Compute and plot the mandelbrot set with the specified 2 dimensional range 574 # info. 575 def mandelhelp(xmin xmax xstep ymin ymax ystep) 576 for y = ymin, y < ymax, ystep in ( 577 (for x = xmin, x < xmax, xstep in 578 printdensity(mandelconverge(x,y))) 579 : putchard(10) 580 ) 581 582 # mandel - This is a convenient helper function for plotting the mandelbrot set 583 # from the specified position with the specified Magnification. 584 def mandel(realstart imagstart realmag imagmag) 585 mandelhelp(realstart, realstart+realmag*78, realmag, 586 imagstart, imagstart+imagmag*40, imagmag); 587 588 Given this, we can try plotting out the mandelbrot set! Lets try it out: 589 590 :: 591 592 ready> mandel(-2.3, -1.3, 0.05, 0.07); 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 **********++++++++++++++++++++.... ... ..+++++++**************** 622 ***********++++++++++++++++++++++....... .......++++++++***************** 623 ************+++++++++++++++++++++++...... ......++++++++****************** 624 **************+++++++++++++++++++++++.... ....++++++++******************** 625 ***************+++++++++++++++++++++++..... ...+++++++++********************* 626 *****************++++++++++++++++++++++.... ...++++++++*********************** 627 *******************+++++++++++++++++++++......++++++++************************* 628 *********************++++++++++++++++++++++.++++++++*************************** 629 *************************+++++++++++++++++++++++******************************* 630 ******************************+++++++++++++************************************ 631 ******************************************************************************* 632 ******************************************************************************* 633 ******************************************************************************* 634 Evaluated to 0.000000 635 ready> mandel(-2, -1, 0.02, 0.04); 636 **************************+++++++++++++++++++++++++++++++++++++++++++++++++++++ 637 ***********************++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 638 *********************+++++++++++++++++++++++++++++++++++++++++++++++++++++++++. 639 *******************+++++++++++++++++++++++++++++++++++++++++++++++++++++++++... 640 *****************+++++++++++++++++++++++++++++++++++++++++++++++++++++++++..... 641 ***************++++++++++++++++++++++++++++++++++++++++++++++++++++++++........ 642 **************++++++++++++++++++++++++++++++++++++++++++++++++++++++........... 643 ************+++++++++++++++++++++++++++++++++++++++++++++++++++++.............. 644 ***********++++++++++++++++++++++++++++++++++++++++++++++++++........ . 645 **********++++++++++++++++++++++++++++++++++++++++++++++............. 646 ********+++++++++++++++++++++++++++++++++++++++++++.................. 647 *******+++++++++++++++++++++++++++++++++++++++....................... 648 ******+++++++++++++++++++++++++++++++++++........................... 649 *****++++++++++++++++++++++++++++++++............................ 650 *****++++++++++++++++++++++++++++............................... 651 ****++++++++++++++++++++++++++...... ......................... 652 ***++++++++++++++++++++++++......... ...... ........... 653 ***++++++++++++++++++++++............ 654 **+++++++++++++++++++++.............. 655 **+++++++++++++++++++................ 656 *++++++++++++++++++................. 657 *++++++++++++++++............ ... 658 *++++++++++++++.............. 659 *+++....++++................ 660 *.......... ........... 661 * 662 *.......... ........... 663 *+++....++++................ 664 *++++++++++++++.............. 665 *++++++++++++++++............ ... 666 *++++++++++++++++++................. 667 **+++++++++++++++++++................ 668 **+++++++++++++++++++++.............. 669 ***++++++++++++++++++++++............ 670 ***++++++++++++++++++++++++......... ...... ........... 671 ****++++++++++++++++++++++++++...... ......................... 672 *****++++++++++++++++++++++++++++............................... 673 *****++++++++++++++++++++++++++++++++............................ 674 ******+++++++++++++++++++++++++++++++++++........................... 675 *******+++++++++++++++++++++++++++++++++++++++....................... 676 ********+++++++++++++++++++++++++++++++++++++++++++.................. 677 Evaluated to 0.000000 678 ready> mandel(-0.9, -1.4, 0.02, 0.03); 679 ******************************************************************************* 680 ******************************************************************************* 681 ******************************************************************************* 682 **********+++++++++++++++++++++************************************************ 683 *+++++++++++++++++++++++++++++++++++++++*************************************** 684 +++++++++++++++++++++++++++++++++++++++++++++********************************** 685 ++++++++++++++++++++++++++++++++++++++++++++++++++***************************** 686 ++++++++++++++++++++++++++++++++++++++++++++++++++++++************************* 687 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++********************** 688 +++++++++++++++++++++++++++++++++.........++++++++++++++++++******************* 689 +++++++++++++++++++++++++++++++.... ......+++++++++++++++++++**************** 690 +++++++++++++++++++++++++++++....... ........+++++++++++++++++++************** 691 ++++++++++++++++++++++++++++........ ........++++++++++++++++++++************ 692 +++++++++++++++++++++++++++......... .. ...+++++++++++++++++++++********** 693 ++++++++++++++++++++++++++........... ....++++++++++++++++++++++******** 694 ++++++++++++++++++++++++............. .......++++++++++++++++++++++****** 695 +++++++++++++++++++++++............. ........+++++++++++++++++++++++**** 696 ++++++++++++++++++++++........... ..........++++++++++++++++++++++*** 697 ++++++++++++++++++++........... .........++++++++++++++++++++++* 698 ++++++++++++++++++............ ...........++++++++++++++++++++ 699 ++++++++++++++++............... .............++++++++++++++++++ 700 ++++++++++++++................. ...............++++++++++++++++ 701 ++++++++++++.................. .................++++++++++++++ 702 +++++++++.................. .................+++++++++++++ 703 ++++++........ . ......... ..++++++++++++ 704 ++............ ...... ....++++++++++ 705 .............. ...++++++++++ 706 .............. ....+++++++++ 707 .............. .....++++++++ 708 ............. ......++++++++ 709 ........... .......++++++++ 710 ......... ........+++++++ 711 ......... ........+++++++ 712 ......... ....+++++++ 713 ........ ...+++++++ 714 ....... ...+++++++ 715 ....+++++++ 716 .....+++++++ 717 ....+++++++ 718 ....+++++++ 719 ....+++++++ 720 Evaluated to 0.000000 721 ready> ^D 722 723 At this point, you may be starting to realize that Kaleidoscope is a 724 real and powerful language. It may not be self-similar :), but it can be 725 used to plot things that are! 726 727 With this, we conclude the "adding user-defined operators" chapter of 728 the tutorial. We have successfully augmented our language, adding the 729 ability to extend the language in the library, and we have shown how 730 this can be used to build a simple but interesting end-user application 731 in Kaleidoscope. At this point, Kaleidoscope can build a variety of 732 applications that are functional and can call functions with 733 side-effects, but it can't actually define and mutate a variable itself. 734 735 Strikingly, variable mutation is an important feature of some languages, 736 and it is not at all obvious how to `add support for mutable 737 variables <LangImpl07.html>`_ without having to add an "SSA construction" 738 phase to your front-end. In the next chapter, we will describe how you 739 can add variable mutation without building SSA in your front-end. 740 741 Full Code Listing 742 ================= 743 744 Here is the complete code listing for our running example, enhanced with 745 the support for user-defined operators. To build this example, use: 746 747 .. code-block:: bash 748 749 # Compile 750 clang++ -g toy.cpp `llvm-config --cxxflags --ldflags --system-libs --libs core mcjit native` -O3 -o toy 751 # Run 752 ./toy 753 754 On some platforms, you will need to specify -rdynamic or 755 -Wl,--export-dynamic when linking. This ensures that symbols defined in 756 the main executable are exported to the dynamic linker and so are 757 available for symbol resolution at run time. This is not needed if you 758 compile your support code into a shared library, although doing that 759 will cause problems on Windows. 760 761 Here is the code: 762 763 .. literalinclude:: ../../examples/Kaleidoscope/Chapter6/toy.cpp 764 :language: c++ 765 766 `Next: Extending the language: mutable variables / SSA 767 construction <LangImpl07.html>`_ 768 769
