Why no single argument `filter(f::function)`?

Internals & Design
6

Oh wow, I was expecting it to throw an error :sweat_smile:

julia> f() = 5
f (generic function with 1 method)

julia> map(f)
5

This behavior seems to violate any meaningful notion of mapping a collection[s] to another, and it’s not in the docstring. Under what circumstance is this useful?

For comparison:

>>> def f():
...     return 5
...
>>> list(map(f))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: map() must have at least two arguments.