GivenParserPart.cpp

/* Implementation of Recursive-Descent Parser
 * for Mini C-Like Language
 * Programming Assignment 2
 * Fall 2024
*/

#include "parser.h"

map<string, bool> defVar;
map<string, Token> SymTable;

namespace Parser {
	bool pushed_back = false;
	LexItem	pushed_token;

	static LexItem GetNextToken(istream& in, int& line) {
		if( pushed_back ) {
			pushed_back = false;
			return pushed_token;
		}
		return getNextToken(in, line);
	}

	static void PushBackToken(LexItem & t) {
		if( pushed_back ) {
			abort();
		}
		pushed_back = true;
		pushed_token = t;	
	}

}

static int error_count = 0;

int ErrCount()
{
    return error_count;
}

void ParseError(int line, string msg)
{
	++error_count;
	cout << line << ": " << msg << endl;
}

bool IdentList(istream& in, int& line);



//PrintStmt:= PRINT (ExpreList) 
bool PrintStmt(istream& in, int& line) {
	LexItem t;
	//cout << "in PrintStmt" << endl;
	
	t = Parser::GetNextToken(in, line);
	if( t != LPAREN ) {
		
		ParseError(line, "Missing Left Parenthesis");
		return false;
	}
	
	bool ex = ExprList(in, line);
	
	if( !ex ) {
		ParseError(line, "Missing expression list after Print");
		return false;
	}
	
	t = Parser::GetNextToken(in, line);
	if(t != RPAREN ) {
		
		ParseError(line, "Missing Right Parenthesis");
		return false;
	}
	//Evaluate: print out the list of expressions values

	return true;
}//End of PrintStmt


//ExprList:= Expr {,Expr}
bool ExprList(istream& in, int& line) {
	bool status = false;
	//cout << "in ExprList and before calling Expr" << endl;
	status = Expr(in, line);
	if(!status){
		ParseError(line, "Missing Expression");
		return false;
	}
	
	LexItem tok = Parser::GetNextToken(in, line);
	
	if (tok == COMMA) {
		//cout << "before calling ExprList" << endl;
		status = ExprList(in, line);
		//cout << "after calling ExprList" << endl;
	}
	else if(tok.GetToken() == ERR){
		ParseError(line, "Unrecognized Input Pattern");
		cout << "(" << tok.GetLexeme() << ")" << endl;
		return false;
	}
	else{
		Parser::PushBackToken(tok);
		return true;
	}
	return status;
}//End of ExprList