In functional programming, functions are treated as first-class citizens, which means they can be passed around as arguments, returned as values, and even be partially applied.
Partial application is a technique where you create a new function by fixing some of the arguments of an existing function, while leaving others open for later use.
Partial application is especially useful when you have a function that takes multiple arguments, but you only want to fix some of them.
By fixing some arguments, you can create a new function that takes fewer arguments, making it easier to reuse and compose with other functions.
To understand partial application, let’s start with a simple example of a function that takes two arguments and returns their sum:
We can partially apply this function to fix one of the arguments, like this:
In this example, we used the bind method to create a new function
add5, which is the same as the add function, but with the first argument fixed to 5. Now, when we call
add5(3), it returns the sum of 5 and 3, which is 8.
In this example, we created a higher-order function
partiallyApply, which takes a function and an array of fixed arguments, and returns a new function that applies those fixed arguments when called.
The returned function is created using a closure, which allows it to access the fixed arguments when called.
Partial application is a powerful technique in functional programming that can help you write cleaner, more reusable code. It allows you to create new functions by fixing some of the arguments of an existing function, while leaving others open for later use.