Steve Wampler wrote:
> Steve Wampler wrote:
>
>>Steve Graham wrote:
>>
>>
>>>I'm looking for a way to generate every possible combination of n letters
>>>out of a total of m letters.
>>>
>>>For example, if the available letters are A, B, C and I want to generate
>>>all possible 2-letter combinations, it should generate the following:
>>>AB
>>>BA
>>>AC
>>>CA
>>>BC
>>>CB
>>>
>>>I think I've seen a trivial way of doing this in Icon/Unicon but don't
>>>remember. Any ideas?
>>
>>
>>Hi Steve,
>>
>>There's a method comp(s, n) in the IPL (procs/strings.icn) that does what you
>>want. The
>>code is:
>>
>> procedure comb(s, i) #: character combinations
>> local j
>>
>> if i < 1 then fail
>> suspend if i = 1 then !s
>> else s[j := 1 to *s - i + 1] || comb(s[j + 1:0], i - 1)
>>
>> end
>
>
> Actually, in reading your mail again, I think you mean 'permutations', not
> combinations. The following code should work:
>
> procedure permute(s, i)
> local j
>
> if i < 1 then fail
> suspend if i = 1 then !s
> else s[j := 1 to *s] || permute(s[1+:j-1]||s[j+1:0], i-1)
> end
And finally, here's another approach. Note that the semantics are
slightly different, in that this version starts by removing duplicated
letters from the input:
procedure permute(s, i)
if i < 1 then fail
s := cset(s)
suspend if i = 1 then !s
else (c := !s) || permute(s--c, i-1)
end
--
Steve Wampler -- [EMAIL PROTECTED]
The gods that smiled on your birth are now laughing out loud.
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