# Compound Assignments

When writing programs, it is generally necessary to increment a variable. The problem with Lua and many other high-level scripting languages is that they don’t provide an efficient way to do such a this:

```lua
a = a + 13
```

Although this method is simple and straightforward, it becomes inefficient when dealing with large-scale programs and longer variable names. Additionally, the VM needs to reference the value of `a`, add `13` to it, and update the original value of `a`. An operator for actions like this would decrease execution time and improve developer productivity. The following code block shows an example using the `+=` compound assignment.

```lua
a += 13
```

There is a compound assignment operator for each arithmetic and string operation in Lua, such as (`+=`, `-=`, `/=`, `*=`, `^=`, `%=`, and `..=`). Each operation assigns a variable the value of itself with the operation performed on the original value.