1 #include <cctype>
2 #include <cstdio>
3 #include <cstdlib>
4 #include <map>
5 #include <memory>
6 #include <string>
7 #include <vector>
8
9 namespace helper {
10 // Cloning make_unique here until it's standard in C++14.
11 // Using a namespace to avoid conflicting with MSVC's std::make_unique (which
12 // ADL can sometimes find in unqualified calls).
13 template <class T, class... Args>
14 static
15 typename std::enable_if<!std::is_array<T>::value, std::unique_ptr<T>>::type
make_unique(Args &&...args)16 make_unique(Args &&... args) {
17 return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
18 }
19 } // end namespace helper
20
21 //===----------------------------------------------------------------------===//
22 // Lexer
23 //===----------------------------------------------------------------------===//
24
25 // The lexer returns tokens [0-255] if it is an unknown character, otherwise one
26 // of these for known things.
27 enum Token {
28 tok_eof = -1,
29
30 // commands
31 tok_def = -2,
32 tok_extern = -3,
33
34 // primary
35 tok_identifier = -4,
36 tok_number = -5
37 };
38
39 static std::string IdentifierStr; // Filled in if tok_identifier
40 static double NumVal; // Filled in if tok_number
41
42 /// gettok - Return the next token from standard input.
gettok()43 static int gettok() {
44 static int LastChar = ' ';
45
46 // Skip any whitespace.
47 while (isspace(LastChar))
48 LastChar = getchar();
49
50 if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
51 IdentifierStr = LastChar;
52 while (isalnum((LastChar = getchar())))
53 IdentifierStr += LastChar;
54
55 if (IdentifierStr == "def")
56 return tok_def;
57 if (IdentifierStr == "extern")
58 return tok_extern;
59 return tok_identifier;
60 }
61
62 if (isdigit(LastChar) || LastChar == '.') { // Number: [0-9.]+
63 std::string NumStr;
64 do {
65 NumStr += LastChar;
66 LastChar = getchar();
67 } while (isdigit(LastChar) || LastChar == '.');
68
69 NumVal = strtod(NumStr.c_str(), nullptr);
70 return tok_number;
71 }
72
73 if (LastChar == '#') {
74 // Comment until end of line.
75 do
76 LastChar = getchar();
77 while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');
78
79 if (LastChar != EOF)
80 return gettok();
81 }
82
83 // Check for end of file. Don't eat the EOF.
84 if (LastChar == EOF)
85 return tok_eof;
86
87 // Otherwise, just return the character as its ascii value.
88 int ThisChar = LastChar;
89 LastChar = getchar();
90 return ThisChar;
91 }
92
93 //===----------------------------------------------------------------------===//
94 // Abstract Syntax Tree (aka Parse Tree)
95 //===----------------------------------------------------------------------===//
96 namespace {
97 /// ExprAST - Base class for all expression nodes.
98 class ExprAST {
99 public:
~ExprAST()100 virtual ~ExprAST() {}
101 };
102
103 /// NumberExprAST - Expression class for numeric literals like "1.0".
104 class NumberExprAST : public ExprAST {
105 double Val;
106
107 public:
NumberExprAST(double Val)108 NumberExprAST(double Val) : Val(Val) {}
109 };
110
111 /// VariableExprAST - Expression class for referencing a variable, like "a".
112 class VariableExprAST : public ExprAST {
113 std::string Name;
114
115 public:
VariableExprAST(const std::string & Name)116 VariableExprAST(const std::string &Name) : Name(Name) {}
117 };
118
119 /// BinaryExprAST - Expression class for a binary operator.
120 class BinaryExprAST : public ExprAST {
121 char Op;
122 std::unique_ptr<ExprAST> LHS, RHS;
123
124 public:
BinaryExprAST(char Op,std::unique_ptr<ExprAST> LHS,std::unique_ptr<ExprAST> RHS)125 BinaryExprAST(char Op, std::unique_ptr<ExprAST> LHS,
126 std::unique_ptr<ExprAST> RHS)
127 : Op(Op), LHS(std::move(LHS)), RHS(std::move(RHS)) {}
128 };
129
130 /// CallExprAST - Expression class for function calls.
131 class CallExprAST : public ExprAST {
132 std::string Callee;
133 std::vector<std::unique_ptr<ExprAST>> Args;
134
135 public:
CallExprAST(const std::string & Callee,std::vector<std::unique_ptr<ExprAST>> Args)136 CallExprAST(const std::string &Callee,
137 std::vector<std::unique_ptr<ExprAST>> Args)
138 : Callee(Callee), Args(std::move(Args)) {}
139 };
140
141 /// PrototypeAST - This class represents the "prototype" for a function,
142 /// which captures its name, and its argument names (thus implicitly the number
143 /// of arguments the function takes).
144 class PrototypeAST {
145 std::string Name;
146 std::vector<std::string> Args;
147
148 public:
PrototypeAST(const std::string & Name,std::vector<std::string> Args)149 PrototypeAST(const std::string &Name, std::vector<std::string> Args)
150 : Name(Name), Args(std::move(Args)) {}
151 };
152
153 /// FunctionAST - This class represents a function definition itself.
154 class FunctionAST {
155 std::unique_ptr<PrototypeAST> Proto;
156 std::unique_ptr<ExprAST> Body;
157
158 public:
FunctionAST(std::unique_ptr<PrototypeAST> Proto,std::unique_ptr<ExprAST> Body)159 FunctionAST(std::unique_ptr<PrototypeAST> Proto,
160 std::unique_ptr<ExprAST> Body)
161 : Proto(std::move(Proto)), Body(std::move(Body)) {}
162 };
163 } // end anonymous namespace
164
165 //===----------------------------------------------------------------------===//
166 // Parser
167 //===----------------------------------------------------------------------===//
168
169 /// CurTok/getNextToken - Provide a simple token buffer. CurTok is the current
170 /// token the parser is looking at. getNextToken reads another token from the
171 /// lexer and updates CurTok with its results.
172 static int CurTok;
getNextToken()173 static int getNextToken() { return CurTok = gettok(); }
174
175 /// BinopPrecedence - This holds the precedence for each binary operator that is
176 /// defined.
177 static std::map<char, int> BinopPrecedence;
178
179 /// GetTokPrecedence - Get the precedence of the pending binary operator token.
GetTokPrecedence()180 static int GetTokPrecedence() {
181 if (!isascii(CurTok))
182 return -1;
183
184 // Make sure it's a declared binop.
185 int TokPrec = BinopPrecedence[CurTok];
186 if (TokPrec <= 0)
187 return -1;
188 return TokPrec;
189 }
190
191 /// LogError* - These are little helper functions for error handling.
LogError(const char * Str)192 std::unique_ptr<ExprAST> LogError(const char *Str) {
193 fprintf(stderr, "Error: %s\n", Str);
194 return nullptr;
195 }
LogErrorP(const char * Str)196 std::unique_ptr<PrototypeAST> LogErrorP(const char *Str) {
197 LogError(Str);
198 return nullptr;
199 }
200
201 static std::unique_ptr<ExprAST> ParseExpression();
202
203 /// numberexpr ::= number
ParseNumberExpr()204 static std::unique_ptr<ExprAST> ParseNumberExpr() {
205 auto Result = helper::make_unique<NumberExprAST>(NumVal);
206 getNextToken(); // consume the number
207 return std::move(Result);
208 }
209
210 /// parenexpr ::= '(' expression ')'
ParseParenExpr()211 static std::unique_ptr<ExprAST> ParseParenExpr() {
212 getNextToken(); // eat (.
213 auto V = ParseExpression();
214 if (!V)
215 return nullptr;
216
217 if (CurTok != ')')
218 return LogError("expected ')'");
219 getNextToken(); // eat ).
220 return V;
221 }
222
223 /// identifierexpr
224 /// ::= identifier
225 /// ::= identifier '(' expression* ')'
ParseIdentifierExpr()226 static std::unique_ptr<ExprAST> ParseIdentifierExpr() {
227 std::string IdName = IdentifierStr;
228
229 getNextToken(); // eat identifier.
230
231 if (CurTok != '(') // Simple variable ref.
232 return helper::make_unique<VariableExprAST>(IdName);
233
234 // Call.
235 getNextToken(); // eat (
236 std::vector<std::unique_ptr<ExprAST>> Args;
237 if (CurTok != ')') {
238 while (true) {
239 if (auto Arg = ParseExpression())
240 Args.push_back(std::move(Arg));
241 else
242 return nullptr;
243
244 if (CurTok == ')')
245 break;
246
247 if (CurTok != ',')
248 return LogError("Expected ')' or ',' in argument list");
249 getNextToken();
250 }
251 }
252
253 // Eat the ')'.
254 getNextToken();
255
256 return helper::make_unique<CallExprAST>(IdName, std::move(Args));
257 }
258
259 /// primary
260 /// ::= identifierexpr
261 /// ::= numberexpr
262 /// ::= parenexpr
ParsePrimary()263 static std::unique_ptr<ExprAST> ParsePrimary() {
264 switch (CurTok) {
265 default:
266 return LogError("unknown token when expecting an expression");
267 case tok_identifier:
268 return ParseIdentifierExpr();
269 case tok_number:
270 return ParseNumberExpr();
271 case '(':
272 return ParseParenExpr();
273 }
274 }
275
276 /// binoprhs
277 /// ::= ('+' primary)*
ParseBinOpRHS(int ExprPrec,std::unique_ptr<ExprAST> LHS)278 static std::unique_ptr<ExprAST> ParseBinOpRHS(int ExprPrec,
279 std::unique_ptr<ExprAST> LHS) {
280 // If this is a binop, find its precedence.
281 while (true) {
282 int TokPrec = GetTokPrecedence();
283
284 // If this is a binop that binds at least as tightly as the current binop,
285 // consume it, otherwise we are done.
286 if (TokPrec < ExprPrec)
287 return LHS;
288
289 // Okay, we know this is a binop.
290 int BinOp = CurTok;
291 getNextToken(); // eat binop
292
293 // Parse the primary expression after the binary operator.
294 auto RHS = ParsePrimary();
295 if (!RHS)
296 return nullptr;
297
298 // If BinOp binds less tightly with RHS than the operator after RHS, let
299 // the pending operator take RHS as its LHS.
300 int NextPrec = GetTokPrecedence();
301 if (TokPrec < NextPrec) {
302 RHS = ParseBinOpRHS(TokPrec + 1, std::move(RHS));
303 if (!RHS)
304 return nullptr;
305 }
306
307 // Merge LHS/RHS.
308 LHS = helper::make_unique<BinaryExprAST>(BinOp, std::move(LHS),
309 std::move(RHS));
310 }
311 }
312
313 /// expression
314 /// ::= primary binoprhs
315 ///
ParseExpression()316 static std::unique_ptr<ExprAST> ParseExpression() {
317 auto LHS = ParsePrimary();
318 if (!LHS)
319 return nullptr;
320
321 return ParseBinOpRHS(0, std::move(LHS));
322 }
323
324 /// prototype
325 /// ::= id '(' id* ')'
ParsePrototype()326 static std::unique_ptr<PrototypeAST> ParsePrototype() {
327 if (CurTok != tok_identifier)
328 return LogErrorP("Expected function name in prototype");
329
330 std::string FnName = IdentifierStr;
331 getNextToken();
332
333 if (CurTok != '(')
334 return LogErrorP("Expected '(' in prototype");
335
336 std::vector<std::string> ArgNames;
337 while (getNextToken() == tok_identifier)
338 ArgNames.push_back(IdentifierStr);
339 if (CurTok != ')')
340 return LogErrorP("Expected ')' in prototype");
341
342 // success.
343 getNextToken(); // eat ')'.
344
345 return helper::make_unique<PrototypeAST>(FnName, std::move(ArgNames));
346 }
347
348 /// definition ::= 'def' prototype expression
ParseDefinition()349 static std::unique_ptr<FunctionAST> ParseDefinition() {
350 getNextToken(); // eat def.
351 auto Proto = ParsePrototype();
352 if (!Proto)
353 return nullptr;
354
355 if (auto E = ParseExpression())
356 return helper::make_unique<FunctionAST>(std::move(Proto), std::move(E));
357 return nullptr;
358 }
359
360 /// toplevelexpr ::= expression
ParseTopLevelExpr()361 static std::unique_ptr<FunctionAST> ParseTopLevelExpr() {
362 if (auto E = ParseExpression()) {
363 // Make an anonymous proto.
364 auto Proto = helper::make_unique<PrototypeAST>("__anon_expr",
365 std::vector<std::string>());
366 return helper::make_unique<FunctionAST>(std::move(Proto), std::move(E));
367 }
368 return nullptr;
369 }
370
371 /// external ::= 'extern' prototype
ParseExtern()372 static std::unique_ptr<PrototypeAST> ParseExtern() {
373 getNextToken(); // eat extern.
374 return ParsePrototype();
375 }
376
377 //===----------------------------------------------------------------------===//
378 // Top-Level parsing
379 //===----------------------------------------------------------------------===//
380
HandleDefinition()381 static void HandleDefinition() {
382 if (ParseDefinition()) {
383 fprintf(stderr, "Parsed a function definition.\n");
384 } else {
385 // Skip token for error recovery.
386 getNextToken();
387 }
388 }
389
HandleExtern()390 static void HandleExtern() {
391 if (ParseExtern()) {
392 fprintf(stderr, "Parsed an extern\n");
393 } else {
394 // Skip token for error recovery.
395 getNextToken();
396 }
397 }
398
HandleTopLevelExpression()399 static void HandleTopLevelExpression() {
400 // Evaluate a top-level expression into an anonymous function.
401 if (ParseTopLevelExpr()) {
402 fprintf(stderr, "Parsed a top-level expr\n");
403 } else {
404 // Skip token for error recovery.
405 getNextToken();
406 }
407 }
408
409 /// top ::= definition | external | expression | ';'
MainLoop()410 static void MainLoop() {
411 while (true) {
412 fprintf(stderr, "ready> ");
413 switch (CurTok) {
414 case tok_eof:
415 return;
416 case ';': // ignore top-level semicolons.
417 getNextToken();
418 break;
419 case tok_def:
420 HandleDefinition();
421 break;
422 case tok_extern:
423 HandleExtern();
424 break;
425 default:
426 HandleTopLevelExpression();
427 break;
428 }
429 }
430 }
431
432 //===----------------------------------------------------------------------===//
433 // Main driver code.
434 //===----------------------------------------------------------------------===//
435
main()436 int main() {
437 // Install standard binary operators.
438 // 1 is lowest precedence.
439 BinopPrecedence['<'] = 10;
440 BinopPrecedence['+'] = 20;
441 BinopPrecedence['-'] = 20;
442 BinopPrecedence['*'] = 40; // highest.
443
444 // Prime the first token.
445 fprintf(stderr, "ready> ");
446 getNextToken();
447
448 // Run the main "interpreter loop" now.
449 MainLoop();
450
451 return 0;
452 }
453