make graphing function

[blin17]

so I want to program a way to graph a function. i made the function below to make a graph. but how do i get it to accept string condition in the if statement (i don't want to worry about the case if it isn't a valid if statement for now)

for example if i take the // replace with an expression and put x==y, it puts a straight line.

but if i want to consule input "x == y" to make it print out that, how would i do it?

void makeGraph(){
	cout << "Enter n where this creates an nxn graph" << endl;
	int n;
	cin >>  n;/*
	cout << "Enter your plot condition" << endl;
	string condition;
	cin>> condition;
	for (int x = -n; x <= n; x ++){
		for (int y = n; y >= -n; y --){
			if( // replace with an expression){
				cout << "X";
			}
			else if (x == 0 && y == 0){
				cout << '0';
			}
			else if (x == 0){
				cout << '-';
			}
			else if (y == 0){
				cout<< "|";
			}
			else{
				cout<< " ";
			}
		}
		cout <<endl;
	}
	cin.ignore();
	cin.get();
}

[Amleto]

you need to be able to parse the string into something you can evaluate as a function of x and y.

expression parsing isnt a simple one-liner.

e.g. http://www.speqmath.com/tutorials/ex...cpp/index.html