Mastering High Performance with Kotlin

Function composition

To solve the problem described in the previous section, we can just create a new method like this:

fun predicate(student: Student)         = ageMoreThan20(student)         && firstNameStartsWithE(student)         && theLengthOfSecondNameMoreThan5(student)students.filter(::predicate)

Or you can create the method like this:

students.filter(fun(student: Student)         = ageMoreThan20(student)        && firstNameStartsWithE(student)        && theLengthOfSecondNameMoreThan5(student))

By using function composition, we can reach a more elegant solution like this:

students   .filter(::ageMoreThan20 and ::firstNameStartsWithE and ::theLengthOfSecondNameMoreThan5)

Function composition is the combining of two or more functions to create a new function. It's a powerful approach ...