Apply Predicate-Based Function

Introduction

In Python, functions are first-class objects, which means that they can be passed around like any other value. One useful application of this is to conditionally apply a function to a value based on some predicate. In this challenge, you will be asked to write a function that takes a predicate function and a function to apply when the predicate is true, and returns a new function that applies the function when the predicate is true.

Skills Graph

Apply Function When True

Problem

Write a function called when that takes two arguments: a predicate function predicate and a function to apply when_true. The when function should return a new function that takes a single argument x. The new function should check if the value of predicate(x) is True. If it is, the new function should call when_true(x) and return the result. Otherwise, the new function should return x.

Example

def double(x):
    return x * 2

def is_even(x):
    return x % 2 == 0

double_even_numbers = when(is_even, double)
double_even_numbers(2) ## 4
double_even_numbers(1) ## 1

Summary

In this challenge, you have written a function that conditionally applies a function to a value based on some predicate. This is a useful technique for creating more flexible and reusable code.