[NTG-context] Re: imposition: getting to the last page of a booklet

[Wolfgang Schuster <wolfgang.schuster.lists@gmail.com>]

Pablo Rodriguez via ntg-context schrieb am 28.02.2024 um 19:02:
> On 2/28/24 12:24, Pablo Rodriguez via ntg-context wrote:
>> [...]
>> This is why beforequadruple would make sense. I guess some Lua magic
>> could do that, computing x to the follwing page that "x % 4 = 3" (and
>> then \page[x]).
>>
>> I will try to find a trick for that, but not now.
> 
> Replying to myself, this is a command to compute next numbers before and
> after quadruples (with application to \realpageno):
> 
>   \starttext
>    \def\beforequadruplenumber#1%
>      {\ifnum\modulonumber{4}{#1} = 1
>         \the\numexpr #1 + 2
>       \orelse\ifnum\modulonumber{4}{#1} = 2
>         \the\numexpr #1 + 1
>       \orelse\ifnum\modulonumber{4}{#1} = 3
>         \the\numexpr #1 + 4
>        \else
>         \the\numexpr #1 + 3
>       \fi}

\def\beforequadruplenumber#1%
   {\ifcase\numexpr#1+1;4\relax
      \number\numexpr#1+4\relax
    \else
      \number\numexpr#1+3-#1;4\relax
    \fi}

>    \def\afterquadruplenumber#1%
>      {\ifnum\modulonumber{4}{#1} = 1
>         \the\numexpr #1 + 4
>       \orelse\ifnum\modulonumber{4}{#1} = 2
>         \the\numexpr #1 + 3
>       \orelse\ifnum\modulonumber{4}{#1} = 3
>         \the\numexpr #1 + 2
>        \else
>         \the\numexpr #1 +1
>       \fi}

\def\afterquadruplenumber#1%
   {\ifcase\numexpr#1;4\relax
      \number\numexpr#1+1\relax
    \else
      \number\numexpr#1+5-#1;4\relax
    \fi}

Wolfgang
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