[Jprogramming] Listing combinations

[David Vaughan]

Thanks.

I thought that using for. constructs incurred a time penalty, but the version without it is slower:

comb2 is also equivalent to comb , but requires space (and time) exponential in the size of the result.


comb2=: ((= +/"1) |.@:I.@# ]) #:@i.@(2&^)
Why is this?

On 28 Sep 2011, at 01:53, Henry Rich wrote:

> http://www.jsoftware.com/jwiki/Essays/Combinations
> 
> Henry Rich
> 
> On 9/27/2011 8:50 PM, David Vaughan wrote:
>> How could I list all combinations of x!y?
>> 
>> e.g. 2!3 = 3, and the combinations are (1,2), (1,3), (2,3).
>> 
>> Thanks.
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