Module 12 Flash Cards

Front 1

First-Class Function

Back 1

By “first-class” we mean that functions can be computed, passed, stored, etc. wherever other values can be computed, passed, stored, etc.

Front 2

Higher-Order Function

Back 2

The term higher-order function just refers to a function that takes or returns other functions.

Front 3

Generic Types (Parametic Polymorphism)

Back 3

This is called parametric polymorphism, or perhaps more commonly generic types. It lets functions take arguments of any type. It is a separate issue from first-class functions:

There are functions that take functions and do not have polymorphic types

There are functions with polymorphic types that do not take functions.

Front 4

Anonymous Function

Back 4

fun triple_n_times (n,x) = n_times((fn y => 3*y), n, x)

This code defines an anonymous function fn y => 3*y. It is a function that takes an argument y and has body 3*y. The fn is a keyword and => (not =) is also part of the syntax. We never gave the function a name (it is anonymous, see?), which is convenient because we did not need one. We just wanted to pass a function to n_times, and in the body of n_times, this function is bound tof.