Re: string generation


In article <lnvf5bvmag.fsf@xxxxxxxxxxxxxxx>, Keith Thompson <kst-u@xxxxxxx> writes:
> "Emmanuel Delahaye" <emdel@xxxxxxxxxxxxxx> writes:
> > Ken Human wrote on 22/05/05 :
> >> I want to generate every possible 16 character combination of the
> >> characters 0-9, A-Z, and a-z programatically. My current code
> >> follows:
> >
> > Really ? It may take hours or days to print them out... Sounds like a
> > cracking device...
>
> Hours or days? You'd better buy a sweater; it's going to get chilly
> after the sun burns out (which will happen long before this thing is
> finished).

Yes, but it still sounds like a cracking device, Dangermouse!

Of course, there's no need to generate them anyway. We already have
the list, in a handy compressed form that allows random access. Just
pick an integer between 0 and 62**16-1 and convert it into its base-
62 representation. A function implementing that algorithm serves as
the "array" of values, and its parameter as the "index".

Iteration is slower than iterating through an actual array, but since
constructing the actual array is, er, infeasible, that hardly matters.

(64 characters would actually be better here, since converting a
number in "pure binary" representation to base 64 is easier than
converting to base 62, but neither is difficult.)

--
Michael Wojcik michael.wojcik@xxxxxxxxxxxxxx

Push up the bottom with your finger, it will puffy and makes stand up.
-- instructions for "swan" from an origami kit
.

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