Holes

(THIS IS VERY WIP)

This is a personal project to play around with making short callables (e.g lambdas) by only defining the body.

It introduces a new Hole object (exported as _) which can be used in arithmetic expressions to build a callable e.g.

from holes import _

double = _ * 2
assert double(5) == 10

In this case, _ * 2 is roughly equivalent to lambda _: _ * 2.

A hole can be used multiple times in the same expression just like a parameter. For example, the above example could be rewritten as

from holes import _

double = _ + _
assert double(5) == 10

assert list(map(_ * 2, [1, 2, 3])) == [2, 4, 6]

Limitations and Differences

The lambda keyword introduces a new scope which means the entirety of the body is executed when it is called.

Lambdas created using Holes do not create a new scope and so care must be taken with how they are built

from holes import _

f = lambda _: print(_)
f(5)   # Prints "5"

f = print(_)  # Eagerly prints the Hole object `_`
f(5)  # Raises an attribute error as f is None (the result of print)