In this tutorial you will learn how to use the extended assignment operators.
It's very common to see statement like the following, where you're adding something to a variable.
sum = sum + currentValue;
i = i + 2;
A shortcut way to write assignments like this is to use the += operator.
It's one operator symbol so don't put blanks between the + and =.
With this notation it isn't necessary to repeat the variable that is being assigned to.
// Same as "sum = sum + currentValue" sum += currentValue; // Same as "i = i + 2" i += 2;
You can use this style with all arithmetic operators (+, -, *, /, and even %).
measurementRange /= 2; // Divides measurementRange by 2. accountBalance -= withdrawal; // Subtracts withdrawal from accountBalance.
There are four ways to add one to a variable. Many languages only support the first way. Current compilers translate them into equivalent code, so there's no efficiency difference, unlike early C compilers where ++ was more efficient.
i = i + 1; // Common in all languages. i += 1; // Common when adding values other than one. i++; // Most common, but only works for adding one. ++i; // Least common.
This notation can also be used with the bit operators (^, &, |). It can not be used with the logical short-circuit operators && and ||, but you can use the & and | versions. It can only be used with binary (two operand) operators, not unary operators.
For simple variables, which kind of assignment to use is mainly a style or readability difference. However, when assigning to l-values that require computation, there is a real difference, both in performance and possible side-effects.
a[f(x)] = a[f(x)] + 1; // Calls f(x) twice! a[f(x)] += 1; // Calls f(x) only once.