I have a question regarding a loop I don't fully understand.
Here's the problem: We are writing a calculator, and we wan't him to not only understand simple expressions like 5+5 but also 5+7-1.
Here's the part of the code I have problems with:
cin >> lval; //read left most number
if (!cin) error("No first operand");
while (cin >> op) //Repeatedly read operand and right value
cin >> rval;
if (!cin) error("No second operand");
First we read in the left value, fine.
Then the loop starts and we read in op, the operator, and in the loop we read in the right value.
What I don't understand is how the loop ever returns to the "cin >> op" part,
if we enter 5 (lval), + (op), and 5 (rval), how will the program understand another operator (like -) will be read into the "op" variable instead of rval?
Thanks in advance.