In order to use in various map-expressions, we need a couple of function that - for simplicity - need to increment a number:

examples/advanced/create_incrementors.py
#!/usr/bin/env python
from __future__ import print_function

def f3(x):
    return x + 3

def f7(x):
    return x + 7

def f23(x):
    return x + 23

print(f3(2))    #  5
print(f7(3))    # 10
print(f3(4))    #  7
print(f7(10))   # 17
print(f23(19))  # 42