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#include "cps/Parser.h"
using namespace cps;
Parser::Parser(Lexer &L) : Lex(L) {
getNextToken();
BinopPrecedence[tok_eq] = 10;
BinopPrecedence[tok_ne] = 10;
BinopPrecedence[tok_le] = 10;
BinopPrecedence[tok_ge] = 10;
BinopPrecedence['<'] = 10;
BinopPrecedence['>'] = 10;
BinopPrecedence['+'] = 20;
BinopPrecedence['-'] = 20;
BinopPrecedence['*'] = 40;
BinopPrecedence['/'] = 40;
}
int Parser::GetTokPrecedence() {
if (BinopPrecedence.find(CurTok) == BinopPrecedence.end()) return -1;
int TokPrec = BinopPrecedence[CurTok];
if (TokPrec <= 0) return -1;
return TokPrec;
}
std::unique_ptr<ExprAST> Parser::ParseParenExpr() {
getNextToken();
auto V = ParseExpression();
if (!V) return nullptr;
if (CurTok != ')') {
fprintf(stderr, "Error: expected ')'\n");
return nullptr;
}
getNextToken();
return V;
}
std::unique_ptr<ExprAST> Parser::ParsePrimary() {
switch (CurTok) {
case tok_identifier: return ParseIdentifierExpr();
case tok_number: return ParseNumberExpr();
case '(': return ParseParenExpr();
default:
fprintf(stderr, "Error: unknown token when expecting an expression\n");
return nullptr;
}
}
std::unique_ptr<ExprAST> Parser::ParseBinOpRHS(int ExprPrec, std::unique_ptr<ExprAST> LHS) {
while (true) {
int TokPrec = GetTokPrecedence();
if (TokPrec < ExprPrec)
return LHS;
int BinOp = CurTok;
getNextToken();
auto RHS = ParsePrimary();
if (!RHS) return nullptr;
int NextPrec = GetTokPrecedence();
if (TokPrec < NextPrec) {
RHS = ParseBinOpRHS(TokPrec + 1, std::move(RHS));
if (!RHS) return nullptr;
}
LHS = std::make_unique<BinaryExprAST>(BinOp, std::move(LHS), std::move(RHS));
}
}
int Parser::getNextToken() {
return CurTok = Lex.gettok();
}
std::unique_ptr<ExprAST> Parser::ParseNumberExpr() {
auto Result = std::make_unique<NumberExprAST>(Lex.NumVal);
getNextToken();
return Result;
}
std::unique_ptr<ExprAST> Parser::ParseIdentifierExpr() {
std::string IdName = Lex.IdentifierStr;
getNextToken();
return std::make_unique<VariableExprAST>(IdName);
}
std::unique_ptr<ExprAST> Parser::ParseExpression() {
auto LHS = ParsePrimary();
if (!LHS) return nullptr;
return ParseBinOpRHS(0, std::move(LHS));
}
std::vector<std::unique_ptr<StmtAST>> Parser::Parse() {
std::vector<std::unique_ptr<StmtAST>> Statements;
while (CurTok != tok_eof) {
if (auto Stmt = ParseStatement()) {
Statements.push_back(std::move(Stmt));
} else {
if (CurTok != tok_eof) getNextToken();
}
}
return Statements;
}
std::unique_ptr<StmtAST> Parser::ParseIfStmt() {
getNextToken();
auto Cond = ParseExpression();
if (!Cond) return nullptr;
if (CurTok != tok_then) {
fprintf(stderr, "Error: expected THEN\n");
return nullptr;
}
getNextToken();
std::vector<std::unique_ptr<StmtAST>> ThenStmts;
while (CurTok != tok_else && CurTok != tok_endif && CurTok != tok_eof) {
auto Stmt = ParseStatement();
if (Stmt) ThenStmts.push_back(std::move(Stmt));
}
std::vector<std::unique_ptr<StmtAST>> ElseStmts;
if (CurTok == tok_else) {
getNextToken();
while (CurTok != tok_endif && CurTok != tok_eof) {
auto Stmt = ParseStatement();
if (Stmt) ElseStmts.push_back(std::move(Stmt));
}
}
if (CurTok != tok_endif) {
fprintf(stderr, "Error: expected ENDIF\n");
return nullptr;
}
getNextToken();
return std::make_unique<IfStmtAST>(std::move(Cond), std::move(ThenStmts), std::move(ElseStmts));
}
std::unique_ptr<StmtAST> Parser::ParseStatement() {
// DECLARE
if (CurTok == tok_declare) {
getNextToken();
if (CurTok != tok_identifier) {
fprintf(stderr, "Error: expected identifier after DECLARE\n");
return nullptr;
}
std::string Name = Lex.IdentifierStr;
getNextToken();
if (CurTok != tok_colon) {
fprintf(stderr, "Error: expected ':' after identifier\n");
return nullptr;
}
getNextToken();
if (CurTok != tok_integer_kw) {
fprintf(stderr, "Error: expected INTEGER type\n");
return nullptr;
}
getNextToken();
return std::make_unique<DeclareStmtAST>(Name);
}
// ASSIGNMENT (x <- expr)
else if (CurTok == tok_identifier) {
std::string Name = Lex.IdentifierStr;
getNextToken(); // eat Name
if (CurTok != tok_assign) {
fprintf(stderr, "Error: expected '<-' for assignment\n");
return nullptr;
}
getNextToken();
auto Expr = ParseExpression();
return std::make_unique<AssignStmtAST>(Name, std::move(Expr));
}
// INPUT
else if (CurTok == tok_input) {
getNextToken();
if (CurTok != tok_identifier) {
fprintf(stderr, "Error: expected identifier after INPUT\n");
return nullptr;
}
std::string Name = Lex.IdentifierStr;
getNextToken();
return std::make_unique<InputStmtAST>(Name);
}
// OUTPUT
else if (CurTok == tok_output) {
getNextToken();
auto Expr = ParseExpression();
return std::make_unique<OutputStmtAST>(std::move(Expr));
}
// IF
else if (CurTok == tok_if) {
return ParseIfStmt();
}
return nullptr;
}
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