\startenvironment metafun-environment-sample

\startuseMPgraphic{sample setup}
    numeric Scale ; Scale := 2cm ;
    numeric Size ; Size := 2.5mm/Scale ;
    numeric Pen ; Pen := .25mm/Scale ;
    path Path ;
    pickup pencircle scaled (4Pen) ;
    def InRed    = withcolor .625red    enddef ;
    def InYellow = withcolor .625yellow enddef ;
    def InGray   = withpen pencircle scaled   Pen  withcolor .625white enddef ;
    def InBetween= withpen pencircle scaled (4Pen) withcolor .800white enddef ;
    def InBlack  = withpen pencircle scaled   Pen                      enddef ;
    def InWhite  = withpen pencircle scaled   Pen  withcolor     white enddef ;
    def DrawArrow text t =
        draw      t ; Path := boundingbox currentpicture ;
        drawarrow t ; setbounds currentpicture to Path ;
    enddef ;
    def ColorCircle =
        fill llcircle withcolor .625red    ;
        fill lrcircle withcolor .625green  ;
        fill urcircle withcolor .625blue   ;
        fill ulcircle withcolor .625yellow ;
    enddef ;
    evenly   := dashpattern(on (3mm/Scale) off (3mm/Scale)) ;
    withdots := dashpattern(off (2.5mm/Scale) on 0 off (2.5mm/Scale)) ;
    ahlength := 4mm/Scale ; ahangle := 30 ;
    draw (origin shifted (0,Size)--origin shifted (0,-Size)) ;
    draw (origin shifted (Size,0)--origin shifted (-Size,0)) ;
    picture Origin ; Origin := currentpicture ;
    setbounds Origin to origin--cycle ;
    currentpicture := nullpicture ;
\stopuseMPgraphic

\startuseMPgraphic{sample finish}
    draw boundingbox currentpicture InBlack ;
    draw Origin InGray ;
    currentpicture := currentpicture scaled Scale ;
\stopuseMPgraphic

% fm = metafun  macro
% fv = metafun  variable
% mc = metapost concept
% mm = metapost macro
% mp = metapost primitive
% mv = metapost variable

\starttexdefinition unexpanded DoDoSampleHead#1#2#3
    \setbox\scratchbox\vbox {
        \tabskip\zeropoint
        \tt\tfx
        \halign {
            \strut\hss##\unskip\unskip
            \cr#3\cr#1\cr
        }
    }
    \ht\scratchbox\ht\strutbox
    \dp\scratchbox\dp\strutbox
    \noligature{#2}\black
    \hfill
    \box\scratchbox
    \ignorespaces
\stoptexdefinition

\starttexdefinition unexpanded DoSampleHead #1#2#3
    \processaction
        [#1]
        [fm=>\DoDoSampleHead{metafun      macro}{#2}{#3},
         fv=>\DoDoSampleHead{metafun   variable}{#2}{#3},
         mc=>\DoDoSampleHead{metapost   concept}{#2}{#3},
         mm=>\DoDoSampleHead{metapost     macro}{#2}{#3},
         mp=>\DoDoSampleHead{metapost primitive}{#2}{#3},
         mv=>\DoDoSampleHead{metapost  variable}{#2}{#3}]
\stoptexdefinition

\starttexdefinition unexpanded SampleHead #1#2#3
    \expanded{\extrosubject{\DoSampleHead{#1}{#2}{\detokenize{#3}}}}
\stoptexdefinition

\starttexdefinition unexpanded StartSample
    \doquintuplegroupempty\doStartSample
\stoptexdefinition

\starttexdefinition unexpanded StopSample
    % dummy
\stoptexdefinition

\starttexdefinition unexpanded doStartSample #1#2#3#4#5#6 StopSample
    \bgroup
    \SampleHead{#1}{#2}{#3}
    \startuseMPgraphic{dummy}
        \includeMPgraphic{sample setup}
        #6
        \includeMPgraphic{sample finish}
    \stopuseMPgraphic
    \blank[samepage]
    \startlinecorrection[blank]
        \useMPgraphic{dummy}
    \stoplinecorrection
    \egroup
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleZ #1#2#3
    \bgroup
    \SampleHead{#1}{#2}{}
    \blank[samepage]
    #3
    \par
    \egroup
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleA #1#2#3
    \StartSample{#1}{#2}{#3}
        path p ; p := #3 ; % freeze randomized
        if length(p)>0 :
            DrawArrow  p InRed ;
        fi ;
        drawpoints p InBetween ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleB #1#2#3#4
    \StartSample{#1}{#2}{#4}
        DrawArrow (#3) InRed ;
        DrawArrow (#4) InYellow ;
        drawpoints (#3) InBetween ;
        drawpoints (#4) InBetween ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleC #1#2#3#4
    \StartSample{#1}{#2}{#4}
        path bb ; bb := boundingbox #3 ;
        DrawArrow #3 InRed ;
        draw #4 withpen pencircle scaled .15 InYellow ;
        setbounds currentpicture to bb ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleD #1#2#3#4
    \StartSample{#1}{#2}{#4}
        DrawArrow #3 InRed ;
        setbounds currentpicture to #4 ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleDD #1#2#3#4
    \StartSample{#1}{#2}{#4}
        DrawArrow #3 InRed ;
        DrawArrow #4 InYellow ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleE #1#2#3#4
    \StartSample{#1}{#2}{#4}
        fill fullcircle scaled 1cm InRed ;
        currentpicture := currentpicture #3 ;
        Scale := 1 ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleF #1#2#3#4
    \StartSample{#1}{#2}{#4}
        DrawArrow #3 InRed ;
        drawdot   #4 InYellow ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleG #1#2#3#4
    \StartSample{#1}{#2}{#4}
        draw    #3 InRed ;
        drawdot #4 InYellow ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleH #1#2#3#4#5
    \StartSample{#1}{#2}{#5}
        DrawArrow #3 InRed ;
        DrawArrow #4 InYellow ;
        drawdot   #5 InWhite ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleHH #1#2#3
    \StartSample{#1}{#2}{#3}
        draw #3 InRed ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleI #1#2#3
    \StartSample{#1}{#2}{#3}
        draw fullcircle InRed #3 ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleII #1#2#3
    \StartSample{#1}{#2}{#3}
        draw fullcircle #3 InRed ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleJ #1#2#3
    \StartSample{#1}{withpen #2}{withpen #3 scaled 2mm}
        draw fullcircle xscaled 2 withpen #3 scaled Pen InRed ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleK #1#2#3
    \StartSample{#1}{withpen #2}{withpen #3}
        draw fullcircle xscaled 2 withpen #3 InRed ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleL #1#2#3
    \StartSample{#1}{#2}{#2 #3}
        #2 #3 InRed;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleM #1#2#3
    \StartSample{#1}{#2}{#2 #3}
        fill boundingbox (#3--cycle) InRed ;
        #2 #3 ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleN #1#2#3#4
    \StartSample{#1}{#2}{#3}
        #3 ;
        draw #4 withpen pencircle scaled 25Pen InRed ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleO #1#2#3
    \StartSample{#1}{#2}{#3}
        drawdot origin InRed ;
        #3 scaled (2.5/Scale) InYellow ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleP #1#2#3
    \StartSample{#1}{#2}{#3}
        drawdot origin InRed ;
        #3 scaled (2.5/Scale) InYellow ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleQ #1#2#3
    \StartSample{#1}{#2}{#3}
        #2 #3 withpen pencircle scaled 25Pen InRed ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleQQ #1#2#3
    \StartSample{#1}{#2}{#3}
        #3 scaled (2.5/Scale) withpen pencircle scaled Pen InYellow ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleQQQ #1#2#3
    \StartSample{#1}{#2}{#3}
        #3 scaled (2.5/Scale) withpen pencircle scaled Pen ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleR #1#2#3
    \StartSample{#1}{#2}{#3}
        ColorCircle ;
        addto currentpicture also (#3) shifted (bbwidth(currentpicture)+.1,0) ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleS #1#2#3
    \StartSample{#1}{#2}{#3}
        Pen := Pen * Scale ; Scale := 1 ; #3 ;%
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleT #1#2#3#4
    \StartSample{#1}{#2}{#3}
        #4 ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleU #1#2#3
    \StartSample{#1}{#2}{#3}
        Scale := Scale / 5 ;
        #3 ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleUU #1#2#3
    \StartSample{#1}{#2}{#3}
        Scale := Scale / 10 ;
        #3 ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleV #1#2#3#4
    \StartSample{#1}{#2}{#3}
        Scale := Scale / 5 ;
        Pen := Pen * 20 ;
        #4 ;
        Pen := Pen / 20 ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleW #1#2#3#4
    \StartSample{#1}{#2}{#3}
        Scale := 1 ;
        #4 ;
    \StopSample
\stoptexdefinition

\starttexdefinition unexpanded ShowSampleX #1#2#3
    \StartSample{#1}{#2}{#3}
        #3 InRed ;
    \StopSample
\stoptexdefinition

\stopenvironment