How a function can be applied on top of another function like ***a(b)(x,y)*** where **a** and **b**-CodePudding

How a function can be applied on top of another function like a(b)(x,y) where a and b are functions and x and y are arguments? Can somebody provide me with the term we call this concept along with some examples.

CodePudding user response：

For a(b)(x, y) to make sense, a needs to be a function that takes b as an argument and produces a new function that takes two arguments. Here's an example:

>>> def a(func):
...     def wrapped(x, y):
...         return 2 * func(x, y)
...     return wrapped
...
>>> def b(x, y):
...     return x   y
...
>>> a(b)(1, 2)
6

In the above example a is a function that wraps a two-argument function and doubles its result. b(1, 2) is 3, and a(b)(1, 2) is therefore 6.

CodePudding user response：

a function can be applied to another function like this

 a(b)(x,y)

if the returned value from a(b) is a function that takes 2 arguments in that case the function that is returned from a(b) will be applied on the parameters x,y

for example :

def mul(x,y):
    return x*y

def add5_to_func(func):
    return lambda x,y : func(x,y)   5

print(add5_to_func(mul)(3,3)) # will print 14