【CS 61a Study notes1】- Higher-order function

Higher-order function

Def : A funtion returns a function or takes a function as an argument

Why higher-order function

High-order functions separate the functions into different parts to reduce the repetition

Higher-order func example

We wanna to get the inverse of the square function by using the search func

def search(f):
	x = 0
	while True:
		if f(x):
			return x 
		x += 1
		
def square(x):
	return x*x

def inverse(f):
	""" return g(y) such that g(f(x))=x """
	return lambda y : search(lambda x : f(x)==y)
		

The return part of the inverse function seems difficult to figure out , so now we can use nesting structure to rewrite it to make it clearer.

# ref: lambda function : lambda x : f(x)==y
def anonymous_func(x):
	return f(x)==y

# let's begin:
def inverse(f):
	def inverse_of_f(y):
		def is_inverse_of_y(x):
			return f(x