Combining Currying and Composition

Function with one parameter value

Composing is easy when we have a scenario like this:

• Function ONE accepts a parameter of type A and returns a value of type B.
• Function TWO accepts a parameter of type B and returns a value of type C.
• Function THREE accepts a parameter of type C and returns a value of type D.

Note how function TWO needs a value that function ONE can provide, while function THREE needs a value produced by function TWO. This means that these functions can be composed. We run function ONE with the value of type A, which returns a value of type B. Next up is function TWO, which receives the value of type B and returns a value of type C. This value of type C is passed to function THREE. Finally, this gives us our result, a value of type D.

Note: In a Haskell or F# type of notation, the signatures of the functions above will be as follows:

ONE :: A -> B
TWO :: B -> C
THREE :: C -> D
COMBINED :: A -> D

Function with multiple parameter values

We saw that if the output of one function matches the input of the other, we can combine them. However, what if function TWO needs multiple arguments? Let’s look at an example.