Is there a trick to reduce the number of counters in the following case?

Question

I want to avoid using \tmp. Is it possible to remove it while keeping the same output?

enter image description here

% Declare counters.
\newcount\pages% \pages is given so you cannot remove it!
\newcount\x
\newcount\tmp

% Initializing.
\pages=9% Try it for an odd or even integer.
\tmp=\pages
\advance\tmp by 1
\x=1

\loop
    \ifnum\x<\tmp
    \noindent\hfill\the\x
    \advance\x by 1
    \ifnum\x>\pages
        \hfill\null\endgraf
    \else
        \hfill\the\x\hfill\null\endgraf
    \fi
    \advance\x by 1
\repeat

\bye

Note: Please don't use e-TeX extension as I am learning Knuth's original TeX right now.

It might be handy to specify if a solution can use the e-TeX extensions, or has to stick to Knuth's TeX only. — Joseph Wright, Jul 06 '12 at 18:32
@HiggsBoson: Not that it doesn't feel sort of like cheating, but still: http://tex.stackexchange.com/questions/60099/who-doesnt-use-e-tex — Ryan Reich, Jul 06 '12 at 19:34
@RyanReich: OK. Thanks. I will learn the extension later after grasping Knuth's original TeX. — kiss my armpit, Jul 07 '12 at 03:56

score 5 · Accepted Answer · answered Jul 06 '12 at 19:35

5

Start with \x=0, step it as soon as possible and invert the inner conditional:

\newcount\pages % \pages is given so you cannot remove it!
\newcount\x

% Initializing.
\pages=9 % Try it for an odd or even integer.
\x=0

\loop
  \ifnum\x<\pages
  \advance\x by 1
  \noindent\hfill\the\x
  \ifnum\x<\pages
    \advance\x by 1
    \hfill\the\x
  \fi
  \hfill\null\endgraf
\repeat

\bye

answered Jul 06 '12 at 19:35

egreg

1,121,712

The most compact solution! – kiss my armpit Jul 07 '12 at 03:53

Joseph Wright · Answer 2 · 2012-07-06T19:02:31.657

4

What's wrong with simply testing for equality at the end of the loop:

% Declare counters.
\newcount\pages% \pages is given so you cannot remove it!
\newcount\x

% Initializing.
\pages=9 % Try it for an odd or even integer.

\x=1 %

\loop
  \ifnum\x=\pages
    \noindent
    \hfill
    \number\x
    \hfill
    \null
    \endgraf
  \fi
  \ifnum\x<\pages
    \noindent
    \hfill
    \number\x
    \advance\x by 1 %
    \hfill
    \number\x
    \hfill
    \null
    \endgraf
    \advance\x by 1 %
\repeat

\bye

(I've added in a few spaces to correctly terminate numbers.)

edited Jul 06 '12 at 19:02

answered Jul 06 '12 at 18:19

Joseph Wright

259,911
34
706
1,036

\pages=1 does not work. :-) – kiss my armpit Jul 06 '12 at 18:24
@HiggsBoson I've updated the answer to cover the no-loop case. – Joseph Wright Jul 06 '12 at 18:30
Defining \printpage seems to be unnecessary. Why don't you put its body directly into the first \ifnum? – kiss my armpit Jul 06 '12 at 19:01
1

@HiggsBoson Oops: I was experimenting with a few approaches, and forgot that I could remove that auxiliary! – Joseph Wright Jul 06 '12 at 19:02
Sorry, I switched to egreg's solution because of the minimal number of used characters. – kiss my armpit Jul 07 '12 at 09:39

David Carlisle · Answer 3 · 2012-07-07T10:25:30.853

4

You got rid of \tmp in your answer, this removes \x as well.

% Declare counters.
\newcount\pages% \pages is given so you cannot remove it!

% Initializing.
\pages=9% Try it for an odd or even integer.


\def\z#1{%
\ifnum#1<\numexpr\pages+1\relax
    \noindent\hfill#1%
  \ifnum#1=\pages
        \hfill\null\endgraf
    \else
        \hfill\number\numexpr#1+1\hfill\null\endgraf
    \fi
    \expandafter\z\expandafter{\number\numexpr#1+2\expandafter\relax\expandafter}%
\fi}
\z1
\bye

edited Jul 07 '12 at 10:25

answered Jul 06 '12 at 18:29

David Carlisle

757,742

Who can compile it? I cannot. – kiss my armpit Jul 06 '12 at 18:37
1

@HiggsBoson Works for me (needs the e-TeX extensions, of course) – Joseph Wright Jul 06 '12 at 18:48
@David: Please why did you use \repeat in place of \fi. If I insert \loop in your conditionals, I will end up with a mess. Also, braces aren't expandable. So you have more than necessary number of \expandafter. I withdrew from editing your answer, but my name is still hanging in there. – Ahmed Musa Jul 07 '12 at 01:16
\repeat is a mistake forgot to change it from the OP's version, of course it worked as it is defined to be \fi but would break a loop as you say. Will edit. The \expandafter is not expanding the brace but the token after it, it is needed to expand the \fi/\repeat token before iteration. – David Carlisle Jul 07 '12 at 10:24

score 2 · Answer 4 · edited Jun 10 '20 at 12:32

2

Using \numexpr\pages+1\relax seems to work:

Code:

% Declare counters.
\newcount\pages% \pages is given so you cannot remove it!
\newcount\x
%\newcount\tmp
% Initializing.
\pages=9% Try it for an odd or even integer.
%\tmp=\pages
%\advance\tmp by 1
\x=1
\loop
    \ifnum\x<\numexpr\pages+1\relax
    \noindent\hfill\the\x
    \advance\x by 1
    \ifnum\x>\pages
        \hfill\null\endgraf
    \else
        \hfill\the\x\hfill\null\endgraf
    \fi
    \advance\x by 1
\repeat
\bye

edited Jun 10 '20 at 12:32

Community

1

answered Jul 06 '12 at 18:12

Peter Grill

223,288

No performance drawback? – kiss my armpit Jul 06 '12 at 18:14
@HiggsBoson: I don't know. That would have to be measured. Just like any other software I would assume that if you are reducing your memory requirements, you are probably increasing the compute time. – Peter Grill Jul 06 '12 at 18:48
Judging performance with these things can be complex: assignments have a time requirement but so do expressions and expansion, so you have to test the real use cases. Lots of assignments will normally be slower than a small number of expressions, but one assignment versus one expression is more difficult! – Joseph Wright Jul 06 '12 at 18:50

Is there a trick to reduce the number of counters in the following case?

4 Answers4

Code: