Promoting Python

[Ian Kelly]

On Wed, Apr 6, 2016 at 8:14 AM, Marko Rauhamaa <marko at pacujo.net> wrote:
> Now, if Python had an unlimited range() iterator/iterable, you could use
> a "for" statement to emulate "while".

You can already do this.

>>> class While:
...     def __init__(self, predicate):
...         self._predicate = predicate
...         self._exited = False
...     def __iter__(self):
...         return self
...     def __next__(self):
...         if self._exited or not self._predicate():
...             self._exited = True
...             raise StopIteration
...
>>> i = 0
>>> for _ in While(lambda: i < 10):
...     print(i)
...     i += 1
...
0
1
2
3
4
5
6
7
8
9


> As it stands, Python without "while" could only compute
> primitive-recursive functions. However, you only need "while" a maximum
> of one time in your whole program to perform an arbitrary computation.

So this is wrong.