Classical FP problem in python : Hamming problem

[Steven Bethard]

Nick Craig-Wood wrote:
> Steven Bethard <steven.bethard at gmail.com> wrote:
> 
>> Nick Craig-Wood wrote:
>>
>>>Thinking about this some more leads me to believe a general purpose
>>>imerge taking any number of arguments will look neater, eg
>>>
>>>def imerge(*generators):
>>>    values = [ g.next() for g in generators ]
>>>    while True:
>>>        x = min(values)
>>>        yield x
>>>        for i in range(len(values)):
>>>            if values[i] == x:
>>>                values[i] = generators[i].next()
>>>
>>
>> This kinda looks like it dies after the first generator is exhausted, 
>> but I'm not certain.
> 
> 
> Yes it will stop iterating then (rather like zip() on lists of unequal
> size). Not sure what the specification should be!  It works for the
> hamming problem though.

Actually, it stops iterating on lists of equal size too:

py> def imerge(*iterators):
...     iterators = [iter(i) for i in iterators]
...     values = [i.next() for i in iterators]
...     while True:
...         x = min(values)
...         yield x
...         for i, val in enumerate(values):
...             if val == x:
...                 values[i] = iterators[i].next()
...
py> list(imerge([1, 4, 7], [2, 5, 8], [3, 6, 9]))
[1, 2, 3, 4, 5, 6, 7]

Note that 8 and 9 are not in the list.

Steve