8 //===----------------------------------------------------------------------===//
10 //===----------------------------------------------------------------------===//
12 // The lexer returns tokens [0-255] if it is an unknown character, otherwise one
13 // of these for known things.
18 tok_def = -2, tok_extern = -3,
21 tok_identifier = -4, tok_number = -5
24 static std::string IdentifierStr; // Filled in if tok_identifier
25 static double NumVal; // Filled in if tok_number
27 /// gettok - Return the next token from standard input.
29 static int LastChar = ' ';
31 // Skip any whitespace.
32 while (isspace(LastChar))
35 if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
36 IdentifierStr = LastChar;
37 while (isalnum((LastChar = getchar())))
38 IdentifierStr += LastChar;
40 if (IdentifierStr == "def") return tok_def;
41 if (IdentifierStr == "extern") return tok_extern;
42 return tok_identifier;
45 if (isdigit(LastChar) || LastChar == '.') { // Number: [0-9.]+
50 } while (isdigit(LastChar) || LastChar == '.');
52 NumVal = strtod(NumStr.c_str(), 0);
56 if (LastChar == '#') {
57 // Comment until end of line.
58 do LastChar = getchar();
59 while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');
65 // Check for end of file. Don't eat the EOF.
69 // Otherwise, just return the character as its ascii value.
70 int ThisChar = LastChar;
75 //===----------------------------------------------------------------------===//
76 // Abstract Syntax Tree (aka Parse Tree)
77 //===----------------------------------------------------------------------===//
79 /// ExprAST - Base class for all expression nodes.
85 /// NumberExprAST - Expression class for numeric literals like "1.0".
86 class NumberExprAST : public ExprAST {
88 NumberExprAST(double val) {}
91 /// VariableExprAST - Expression class for referencing a variable, like "a".
92 class VariableExprAST : public ExprAST {
95 VariableExprAST(const std::string &name) : Name(name) {}
98 /// BinaryExprAST - Expression class for a binary operator.
99 class BinaryExprAST : public ExprAST {
101 BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs) {}
104 /// CallExprAST - Expression class for function calls.
105 class CallExprAST : public ExprAST {
107 std::vector<ExprAST*> Args;
109 CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
110 : Callee(callee), Args(args) {}
113 /// PrototypeAST - This class represents the "prototype" for a function,
114 /// which captures its name, and its argument names (thus implicitly the number
115 /// of arguments the function takes).
118 std::vector<std::string> Args;
120 PrototypeAST(const std::string &name, const std::vector<std::string> &args)
121 : Name(name), Args(args) {}
125 /// FunctionAST - This class represents a function definition itself.
128 FunctionAST(PrototypeAST *proto, ExprAST *body) {}
130 } // end anonymous namespace
132 //===----------------------------------------------------------------------===//
134 //===----------------------------------------------------------------------===//
136 /// CurTok/getNextToken - Provide a simple token buffer. CurTok is the current
137 /// token the parser is looking at. getNextToken reads another token from the
138 /// lexer and updates CurTok with its results.
140 static int getNextToken() {
141 return CurTok = gettok();
144 /// BinopPrecedence - This holds the precedence for each binary operator that is
146 static std::map<char, int> BinopPrecedence;
148 /// GetTokPrecedence - Get the precedence of the pending binary operator token.
149 static int GetTokPrecedence() {
150 if (!isascii(CurTok))
153 // Make sure it's a declared binop.
154 int TokPrec = BinopPrecedence[CurTok];
155 if (TokPrec <= 0) return -1;
159 /// Error* - These are little helper functions for error handling.
160 ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
161 PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
163 static ExprAST *ParseExpression();
167 /// ::= identifier '(' expression* ')'
168 static ExprAST *ParseIdentifierExpr() {
169 std::string IdName = IdentifierStr;
171 getNextToken(); // eat identifier.
173 if (CurTok != '(') // Simple variable ref.
174 return new VariableExprAST(IdName);
177 getNextToken(); // eat (
178 std::vector<ExprAST*> Args;
181 ExprAST *Arg = ParseExpression();
185 if (CurTok == ')') break;
188 return Error("Expected ')' or ',' in argument list");
196 return new CallExprAST(IdName, Args);
199 /// numberexpr ::= number
200 static ExprAST *ParseNumberExpr() {
201 ExprAST *Result = new NumberExprAST(NumVal);
202 getNextToken(); // consume the number
206 /// parenexpr ::= '(' expression ')'
207 static ExprAST *ParseParenExpr() {
208 getNextToken(); // eat (.
209 ExprAST *V = ParseExpression();
213 return Error("expected ')'");
214 getNextToken(); // eat ).
219 /// ::= identifierexpr
222 static ExprAST *ParsePrimary() {
224 default: return Error("unknown token when expecting an expression");
225 case tok_identifier: return ParseIdentifierExpr();
226 case tok_number: return ParseNumberExpr();
227 case '(': return ParseParenExpr();
232 /// ::= ('+' primary)*
233 static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
234 // If this is a binop, find its precedence.
236 int TokPrec = GetTokPrecedence();
238 // If this is a binop that binds at least as tightly as the current binop,
239 // consume it, otherwise we are done.
240 if (TokPrec < ExprPrec)
243 // Okay, we know this is a binop.
245 getNextToken(); // eat binop
247 // Parse the primary expression after the binary operator.
248 ExprAST *RHS = ParsePrimary();
251 // If BinOp binds less tightly with RHS than the operator after RHS, let
252 // the pending operator take RHS as its LHS.
253 int NextPrec = GetTokPrecedence();
254 if (TokPrec < NextPrec) {
255 RHS = ParseBinOpRHS(TokPrec+1, RHS);
256 if (RHS == 0) return 0;
260 LHS = new BinaryExprAST(BinOp, LHS, RHS);
265 /// ::= primary binoprhs
267 static ExprAST *ParseExpression() {
268 ExprAST *LHS = ParsePrimary();
271 return ParseBinOpRHS(0, LHS);
275 /// ::= id '(' id* ')'
276 static PrototypeAST *ParsePrototype() {
277 if (CurTok != tok_identifier)
278 return ErrorP("Expected function name in prototype");
280 std::string FnName = IdentifierStr;
284 return ErrorP("Expected '(' in prototype");
286 std::vector<std::string> ArgNames;
287 while (getNextToken() == tok_identifier)
288 ArgNames.push_back(IdentifierStr);
290 return ErrorP("Expected ')' in prototype");
293 getNextToken(); // eat ')'.
295 return new PrototypeAST(FnName, ArgNames);
298 /// definition ::= 'def' prototype expression
299 static FunctionAST *ParseDefinition() {
300 getNextToken(); // eat def.
301 PrototypeAST *Proto = ParsePrototype();
302 if (Proto == 0) return 0;
304 if (ExprAST *E = ParseExpression())
305 return new FunctionAST(Proto, E);
309 /// toplevelexpr ::= expression
310 static FunctionAST *ParseTopLevelExpr() {
311 if (ExprAST *E = ParseExpression()) {
312 // Make an anonymous proto.
313 PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
314 return new FunctionAST(Proto, E);
319 /// external ::= 'extern' prototype
320 static PrototypeAST *ParseExtern() {
321 getNextToken(); // eat extern.
322 return ParsePrototype();
325 //===----------------------------------------------------------------------===//
327 //===----------------------------------------------------------------------===//
329 static void HandleDefinition() {
330 if (ParseDefinition()) {
331 fprintf(stderr, "Parsed a function definition.\n");
333 // Skip token for error recovery.
338 static void HandleExtern() {
340 fprintf(stderr, "Parsed an extern\n");
342 // Skip token for error recovery.
347 static void HandleTopLevelExpression() {
348 // Evaluate a top-level expression into an anonymous function.
349 if (ParseTopLevelExpr()) {
350 fprintf(stderr, "Parsed a top-level expr\n");
352 // Skip token for error recovery.
357 /// top ::= definition | external | expression | ';'
358 static void MainLoop() {
360 fprintf(stderr, "ready> ");
362 case tok_eof: return;
363 case ';': getNextToken(); break; // ignore top-level semicolons.
364 case tok_def: HandleDefinition(); break;
365 case tok_extern: HandleExtern(); break;
366 default: HandleTopLevelExpression(); break;
371 //===----------------------------------------------------------------------===//
373 //===----------------------------------------------------------------------===//
376 // Install standard binary operators.
377 // 1 is lowest precedence.
378 BinopPrecedence['<'] = 10;
379 BinopPrecedence['+'] = 20;
380 BinopPrecedence['-'] = 20;
381 BinopPrecedence['*'] = 40; // highest.
383 // Prime the first token.
384 fprintf(stderr, "ready> ");
387 // Run the main "interpreter loop" now.