MetaFun - Pragma ADE

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\startuseMPgraphic{third}
\includeMPgraphic{first}
fill fullsquare scaled size withcolor bottomshade ;
fill fullsquare scaled delta withcolor centershade ;
\stopuseMPgraphic
Because both graphics share code, we have defined that code as a separate graphic, that we include.
The only point of interest in this definition is the fact that we let METAPOST interpolate between the
two colors using .5[ ].
\startuseMPgraphic{first}
numeric size, delta ;
size := 2.5cm ; delta := size/3 ;
color mainshade, topshade, bottomshade, centershade ;
mainshade := \MPcolor{funcolor} ;
topshade := .9mainshade ; bottomshade := .5mainshade ;
centershade := .5[topshade,bottomshade] ;
\stopuseMPgraphic
The color funcolor is provided by CONTEXT, and since we want to use this graphic with different
colors, this kind of mapping is quite convenient. The bunch of graphics is packaged in a combination
with empty captions. Note how we set the color before we include the graphic.
\startcombination[5*2]
{\definecolor[funcolor][red] \useMPgraphic{second}} {}
{\definecolor[funcolor][green] \useMPgraphic{second}} {}
{\definecolor[funcolor][blue] \useMPgraphic{second}} {}
{\definecolor[funcolor][yellow]\useMPgraphic{second}} {}
{\definecolor[funcolor][white] \useMPgraphic{second}} {}
{\definecolor[funcolor][red] \useMPgraphic{third}} {}
{\definecolor[funcolor][green] \useMPgraphic{third}} {}
{\definecolor[funcolor][blue] \useMPgraphic{third}} {}
{\definecolor[funcolor][yellow]\useMPgraphic{third}} {}
{\definecolor[funcolor][white] \useMPgraphic{third}} {}
\stopcombination
We use a similar arrangement for the following graphic, where we have replaced the definitions
of first, second and third by new definitions.
The definition of the first row of figure 13.4 is used in the second and third and therefore is the
most complicated. We use quite some scratch variables to reach a high level of abstraction. The
xyscaled operator is a METAFUN macro.
\startuseMPgraphic{first}
numeric height, width, radius, gap ; gap := 1mm ;
height = 2.5cm ; width := height/2 ; radius := height/2.5 ;
color mainshade, leftshade, rightshade, centershade ;
mainshade := \MPcolor{funcolor} ;
leftshade := .9mainshade ; rightshade := .5mainshade ;
centershade := .5[leftshade,rightshade] ;
fill unitsquare xyscaled ( width,height) withcolor leftshade ;
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