Build all combinations of strings

[bearophile via Digitalmars-d-learn]

Nordlöw:

> Couldn't we do a first pass and check that if elements of T are 
> distinct and if so set doCopy to false otherwise true?

The algorithm you have seen in Rosettacode doesn't care if and 
what items of the input sequence are duplicated, it handles them 
as they are all distinct. And them being distinct (or not 
distinct) doesn't change the desire to use something like doCopy 
to have dup-ped output arrays, so I don't understand what you are 
trying to say.

The purpose of doCopy is similar of the difference between 
File.byLine and File.byLineCopy (originally I suggested to give a 
doCopy argiment to byLine too, for safety. Andrei said no. Later 
experience has shown I was right and we have added byLineCopy, 
but now the default line iteration is the non-copying one, that 
is less safe).

Bye,
bearophile