Higher order operators for functional programming in Python.
When using functional programming techniques in Python, we occasionally run into code that looks like this:
filter(lambda x: x < 3, [1, 2, 3, 4, 5])
While ``lambda``s are not exactly complex, it still takes a bit of time for the reader to parse the lambda and figure out what the intent was.
The it object makes the code more readable by capturing the intent without
a lot of syntax:
filter(it < 3, [1, 2, 3, 4, 5])
Behind the scenes, the it object implements Python's magic methods, and
returns a function (a lambda, to be exact), that performs the task of the
construct in which it was used.
Therefore, it < 2 becomes lambda x: x < 2.
The following constructs are supported:
- comparison operators (e.g.,
it < 2,4 >= it) - attribute access (e.g.,
it.foo) - subscript access (e.g.,
it['foo'],it[0],it[-2:]) - function calls (e.g.,
it(1, 2),it(foo='bar')) - mathematical operators (e.g.,
it + 2,20 / it) - binary operators (e.g.,
it & 4,128 | it) - some unary operators (i.e.,
-it,+it, and~it)
Because of the underlying limtiation of the Python language, there are a few
cavats when using it.
The reverse pow(), where it is in the second position, cannot be used
with modulo. For example, pow(2, it, 3) is cause a TypeError.
Since unary operators such as -= do not make much sense for the intended
usage of the it object, they are not implemented. Use the binary operators
(e.g., it - n) instead.
There are no aliases for setting attributes and keys. For example, you are not
allowed to say map(it.foo = 12, ...). It was decided that adding unfamiliar
methods is inferior to simply using lambdas, so support for these constructs was
not added in any form.
Where python already supplies adequate functions, the magic methods were
omitted. For example, str(), int(), bool(), len(), etc, should
be used directly. This is also due to the fact that such function have
expectation about return values of the magic methods which cannot be satisfied.
This code is published under the BSD license. Please see the LICENSE file in
the source tree.