Re: Elementary but surprisingly difficult.

In article <ebemg5-rae.ln1@xxxxxxxxxxxxxxxx>,
Bernd Paysan <bernd.paysan@xxxxxx> wrote:
Slava Pestov wrote:

On May 24, 3:05 pm, Albert van der Horst <alb...@xxxxxxxxxxxxxxxxxx>
wrote:
Even using variables/locals, I find this difficult.
(More difficult then e.g. making a table for the number of
dividers of N, which sounds much less trivial.)

It's not difficult if you have a library of sequence operations:

Nice filter, but doing that in-place is not difficult, either.

I give you a solution for characters in a string, and Albert can generalize
it. It is supposed that the string is sorted, so it will only remove
sequenes of the same character:

: uniquify ( addr u -- addr u' )
over >r bounds dup dup c@ 2swap 1+ ?DO
I c@ tuck <> IF swap 1+ 2dup c! swap THEN LOOP

----------------------------------------------
WANT CASE-INSENSITIVE CASE-INSENSITIVE

WANT TUCK
WANT BOUNDS
WANT DUMP

CREATE AAP 1 C, 1 C, 2 C, 2 C, 3 C, 4 C, 5 C, 5 C, 5 C, 5 C,

: uniquify ( addr u -- addr u' )
over >r bounds dup dup c@ 2swap 1+ ?DO
I c@ tuck <> IF swap 1+ 2dup c! swap THEN LOOP
drop r> swap over - ;

AAP 10 uniquify .

AAP 100 DUMP

----------------------------------------------


albert@apple:~/PROJECT/euler> lina -a
"unique.frt" INCLUDED
4
0805,124C: 0102 0304 |....|
0805,1250: 0504 0505 0505 0000 0800 0000 756E 6971 |............uniq|
0805,1260: 7569 6679 68A7 0408 8012 0508 0000 0000 |uifyh...........|
0805,1270: 2C12 0508 5812 0508 0A05 0508 0000 0000 |,...X...........|
0805,1280: 98A3 0408 B8A1 0408 740A 0508 48A4 0408 |........t...H...|
0805,1290: 48A4 0408 98A5 0408 A8A4 0408 E4AF 0408 |H...............|
0805,12A0: 2C99 0408 3400 0000 6899 0408 98A5 0408 |,...4...h.......|
OK
BYE

----------------------------------------------

So is this a bug in lina, or does it fail the first test
I throw at it?
(I expect 5 of course.)

The code is not transparent enough that it would be of
any value as specification of an algorithm, or in this
case to debug.

--
Bernd Paysan

Groetjes Albert

--
--
Albert van der Horst, UTRECHT,THE NETHERLANDS
Economic growth -- like all pyramid schemes -- ultimately falters.
albert@spe&ar&c.xs4all.nl &=n http://home.hccnet.nl/a.w.m.van.der.horst

.

Relevant Pages