Lexical scoping is a concept in programming languages that determines how the values of variables are assigned in a function. In R, lexical scoping means that the values of free variables are searched for in the environment in which the function was defined, not in the environment in which the function is called.
This is important because it allows us to create functions that are more reusable and flexible. For example, consider the following function:
make.power <- function(n) {
pow <- function(x) {
x^n
}
pow
}
This function takes a number as input and returns a function that raises that number to the power of `n`. The `make.power()` function is defined in the global environment, but the `pow()` function is defined inside the `make.power()` function. This means that the value of `n` in the `pow()` function is determined by the value of `n` when the `make.power()` function is called.
For example, if we call `make.power(3)`, then the value of `n` in the `pow()` function will be 3. This means that the `pow()` function will raise its input to the power of 3.
Benefits
- It makes it easier to debug functions, because you can always see where the values of free variables are coming from.
- It makes it easier to write functions that are independent of the environment in which they are called.
- It can help to improve the performance of functions, because the values of free variables do not have to be recomputed every time the function is called.
