399 lines
10 KiB
C++
399 lines
10 KiB
C++
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#include <cstdio>
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#include <cstdlib>
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#include <string>
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#include <map>
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#include <vector>
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//===----------------------------------------------------------------------===//
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// Lexer
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//===----------------------------------------------------------------------===//
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// The lexer returns tokens [0-255] if it is an unknown character, otherwise one
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// of these for known things.
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enum Token {
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tok_eof = -1,
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// commands
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tok_def = -2, tok_extern = -3,
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// primary
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tok_identifier = -4, tok_number = -5
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};
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static std::string IdentifierStr; // Filled in if tok_identifier
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static double NumVal; // Filled in if tok_number
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/// gettok - Return the next token from standard input.
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static int gettok() {
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static int LastChar = ' ';
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// Skip any whitespace.
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while (isspace(LastChar))
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LastChar = getchar();
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if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
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IdentifierStr = LastChar;
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while (isalnum((LastChar = getchar())))
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IdentifierStr += LastChar;
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if (IdentifierStr == "def") return tok_def;
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if (IdentifierStr == "extern") return tok_extern;
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return tok_identifier;
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}
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if (isdigit(LastChar) || LastChar == '.') { // Number: [0-9.]+
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std::string NumStr;
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do {
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NumStr += LastChar;
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LastChar = getchar();
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} while (isdigit(LastChar) || LastChar == '.');
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NumVal = strtod(NumStr.c_str(), 0);
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return tok_number;
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}
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if (LastChar == '#') {
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// Comment until end of line.
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do LastChar = getchar();
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while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');
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if (LastChar != EOF)
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return gettok();
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}
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// Check for end of file. Don't eat the EOF.
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if (LastChar == EOF)
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return tok_eof;
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// Otherwise, just return the character as its ascii value.
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int ThisChar = LastChar;
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LastChar = getchar();
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return ThisChar;
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}
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//===----------------------------------------------------------------------===//
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// Abstract Syntax Tree (aka Parse Tree)
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//===----------------------------------------------------------------------===//
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/// ExprAST - Base class for all expression nodes.
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class ExprAST {
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public:
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virtual ~ExprAST() {}
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};
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/// NumberExprAST - Expression class for numeric literals like "1.0".
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class NumberExprAST : public ExprAST {
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double Val;
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public:
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NumberExprAST(double val) : Val(val) {}
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};
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/// VariableExprAST - Expression class for referencing a variable, like "a".
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class VariableExprAST : public ExprAST {
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std::string Name;
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public:
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VariableExprAST(const std::string &name) : Name(name) {}
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};
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/// BinaryExprAST - Expression class for a binary operator.
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class BinaryExprAST : public ExprAST {
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char Op;
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ExprAST *LHS, *RHS;
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public:
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BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs)
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: Op(op), LHS(lhs), RHS(rhs) {}
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};
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/// CallExprAST - Expression class for function calls.
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class CallExprAST : public ExprAST {
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std::string Callee;
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std::vector<ExprAST*> Args;
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public:
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CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
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: Callee(callee), Args(args) {}
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};
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/// PrototypeAST - This class represents the "prototype" for a function,
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/// which captures its name, and its argument names (thus implicitly the number
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/// of arguments the function takes).
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class PrototypeAST {
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std::string Name;
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std::vector<std::string> Args;
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public:
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PrototypeAST(const std::string &name, const std::vector<std::string> &args)
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: Name(name), Args(args) {}
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};
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/// FunctionAST - This class represents a function definition itself.
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class FunctionAST {
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PrototypeAST *Proto;
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ExprAST *Body;
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public:
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FunctionAST(PrototypeAST *proto, ExprAST *body)
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: Proto(proto), Body(body) {}
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};
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//===----------------------------------------------------------------------===//
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// Parser
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//===----------------------------------------------------------------------===//
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/// CurTok/getNextToken - Provide a simple token buffer. CurTok is the current
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/// token the parser is looking at. getNextToken reads another token from the
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/// lexer and updates CurTok with its results.
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static int CurTok;
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static int getNextToken() {
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return CurTok = gettok();
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}
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/// BinopPrecedence - This holds the precedence for each binary operator that is
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/// defined.
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static std::map<char, int> BinopPrecedence;
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/// GetTokPrecedence - Get the precedence of the pending binary operator token.
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static int GetTokPrecedence() {
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if (!isascii(CurTok))
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return -1;
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// Make sure it's a declared binop.
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int TokPrec = BinopPrecedence[CurTok];
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if (TokPrec <= 0) return -1;
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return TokPrec;
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}
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/// Error* - These are little helper functions for error handling.
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ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
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PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
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FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
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static ExprAST *ParseExpression();
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/// identifierexpr
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/// ::= identifier
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/// ::= identifier '(' expression* ')'
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static ExprAST *ParseIdentifierExpr() {
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std::string IdName = IdentifierStr;
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getNextToken(); // eat identifier.
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if (CurTok != '(') // Simple variable ref.
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return new VariableExprAST(IdName);
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// Call.
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getNextToken(); // eat (
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std::vector<ExprAST*> Args;
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if (CurTok != ')') {
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while (1) {
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ExprAST *Arg = ParseExpression();
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if (!Arg) return 0;
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Args.push_back(Arg);
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if (CurTok == ')') break;
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if (CurTok != ',')
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return Error("Expected ')' or ',' in argument list");
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getNextToken();
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}
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}
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// Eat the ')'.
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getNextToken();
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return new CallExprAST(IdName, Args);
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}
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/// numberexpr ::= number
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static ExprAST *ParseNumberExpr() {
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ExprAST *Result = new NumberExprAST(NumVal);
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getNextToken(); // consume the number
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return Result;
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}
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/// parenexpr ::= '(' expression ')'
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static ExprAST *ParseParenExpr() {
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getNextToken(); // eat (.
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ExprAST *V = ParseExpression();
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if (!V) return 0;
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if (CurTok != ')')
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return Error("expected ')'");
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getNextToken(); // eat ).
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return V;
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}
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/// primary
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/// ::= identifierexpr
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/// ::= numberexpr
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/// ::= parenexpr
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static ExprAST *ParsePrimary() {
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switch (CurTok) {
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default: return Error("unknown token when expecting an expression");
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case tok_identifier: return ParseIdentifierExpr();
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case tok_number: return ParseNumberExpr();
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case '(': return ParseParenExpr();
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}
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}
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/// binoprhs
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/// ::= ('+' primary)*
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static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
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// If this is a binop, find its precedence.
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while (1) {
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int TokPrec = GetTokPrecedence();
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// If this is a binop that binds at least as tightly as the current binop,
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// consume it, otherwise we are done.
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if (TokPrec < ExprPrec)
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return LHS;
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// Okay, we know this is a binop.
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int BinOp = CurTok;
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getNextToken(); // eat binop
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// Parse the primary expression after the binary operator.
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ExprAST *RHS = ParsePrimary();
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if (!RHS) return 0;
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// If BinOp binds less tightly with RHS than the operator after RHS, let
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// the pending operator take RHS as its LHS.
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int NextPrec = GetTokPrecedence();
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if (TokPrec < NextPrec) {
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RHS = ParseBinOpRHS(TokPrec+1, RHS);
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if (RHS == 0) return 0;
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}
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// Merge LHS/RHS.
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LHS = new BinaryExprAST(BinOp, LHS, RHS);
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}
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}
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/// expression
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/// ::= primary binoprhs
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///
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static ExprAST *ParseExpression() {
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ExprAST *LHS = ParsePrimary();
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if (!LHS) return 0;
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return ParseBinOpRHS(0, LHS);
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}
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/// prototype
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/// ::= id '(' id* ')'
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static PrototypeAST *ParsePrototype() {
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if (CurTok != tok_identifier)
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return ErrorP("Expected function name in prototype");
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std::string FnName = IdentifierStr;
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getNextToken();
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if (CurTok != '(')
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return ErrorP("Expected '(' in prototype");
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std::vector<std::string> ArgNames;
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while (getNextToken() == tok_identifier)
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ArgNames.push_back(IdentifierStr);
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if (CurTok != ')')
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return ErrorP("Expected ')' in prototype");
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// success.
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getNextToken(); // eat ')'.
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return new PrototypeAST(FnName, ArgNames);
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}
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/// definition ::= 'def' prototype expression
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static FunctionAST *ParseDefinition() {
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getNextToken(); // eat def.
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PrototypeAST *Proto = ParsePrototype();
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if (Proto == 0) return 0;
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if (ExprAST *E = ParseExpression())
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return new FunctionAST(Proto, E);
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return 0;
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}
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/// toplevelexpr ::= expression
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static FunctionAST *ParseTopLevelExpr() {
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if (ExprAST *E = ParseExpression()) {
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// Make an anonymous proto.
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PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
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return new FunctionAST(Proto, E);
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}
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return 0;
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}
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/// external ::= 'extern' prototype
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static PrototypeAST *ParseExtern() {
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getNextToken(); // eat extern.
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return ParsePrototype();
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}
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//===----------------------------------------------------------------------===//
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// Top-Level parsing
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//===----------------------------------------------------------------------===//
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static void HandleDefinition() {
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if (ParseDefinition()) {
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fprintf(stderr, "Parsed a function definition.\n");
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} else {
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// Skip token for error recovery.
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getNextToken();
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}
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}
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static void HandleExtern() {
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if (ParseExtern()) {
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fprintf(stderr, "Parsed an extern\n");
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} else {
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// Skip token for error recovery.
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getNextToken();
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}
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}
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static void HandleTopLevelExpression() {
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// Evaluate a top-level expression into an anonymous function.
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if (ParseTopLevelExpr()) {
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fprintf(stderr, "Parsed a top-level expr\n");
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} else {
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// Skip token for error recovery.
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getNextToken();
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}
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}
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/// top ::= definition | external | expression | ';'
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static void MainLoop() {
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while (1) {
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fprintf(stderr, "ready> ");
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switch (CurTok) {
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case tok_eof: return;
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case ';': getNextToken(); break; // ignore top-level semicolons.
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case tok_def: HandleDefinition(); break;
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case tok_extern: HandleExtern(); break;
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default: HandleTopLevelExpression(); break;
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}
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}
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}
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//===----------------------------------------------------------------------===//
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// Main driver code.
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//===----------------------------------------------------------------------===//
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int main() {
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// Install standard binary operators.
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// 1 is lowest precedence.
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BinopPrecedence['<'] = 10;
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BinopPrecedence['+'] = 20;
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BinopPrecedence['-'] = 20;
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BinopPrecedence['*'] = 40; // highest.
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// Prime the first token.
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fprintf(stderr, "ready> ");
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getNextToken();
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// Run the main "interpreter loop" now.
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MainLoop();
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return 0;
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}
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