Introduction To Haskell
Imagine that you have two functions. The return type of the first function is the argument type of the second. When this is true, you can create a new function by pipelining the result of the first function into the second.
Here is an example,
myOdd = not . even
Here, the not and even functions are combined to make a function that returns True if a number is odd.
From the specification,
The operation functional composition combines two functions to get a new function.
Given two functions
- f: A → B
- g: B → C
function g o f, called the composition of g and f, is a function whose domain is A and co-domain is C.
In this example, we define two functions, f and g. Function f adds 5 to its argument. Function g squares its argument.
f :: Integer->Integer f x = x + 5 g :: Integer->Integer g x = x^2 comp :: Integer -> Integer comp = f.g
The comp function is the composition of functions f and g. The result of function g is pipelined to function f.