24 lines
613 B
Markdown
24 lines
613 B
Markdown
---
|
|
title: Apply function when true
|
|
tags: function
|
|
expertise: intermediate
|
|
cover: blog_images/interior-10.jpg
|
|
firstSeen: 2020-01-02T20:25:45+02:00
|
|
lastUpdated: 2020-11-09T23:56:11+02:00
|
|
---
|
|
|
|
Tests a value, `x`, against a testing function, conditionally applying a function.
|
|
|
|
- Check if the value of `predicate()` is `True` for `x` and if so call `when_true()`, otherwise return `x`.
|
|
|
|
```py
|
|
def when(predicate, when_true):
|
|
return lambda x: when_true(x) if predicate(x) else x
|
|
```
|
|
|
|
```py
|
|
double_even_numbers = when(lambda x: x % 2 == 0, lambda x : x * 2)
|
|
double_even_numbers(2) # 4
|
|
double_even_numbers(1) # 1
|
|
```
|