bar graphs, m-graph, sarith

[John Kitzmiller <kitz@inradius.net>]

When trying to make a bar graph with m-graph.mkiv and sarith, the command Ssub (string subtract) seems to Sadd instead. An mwe of a bar graph:

 (data1 is a separate file containing
  01 02
  02 03)

\usemodule[m-graph]
\startMPpage[instance=graph]
input sarith;
draw begingraph(5cm,5cm);
 gdata("data1", v,
          path p;
          augment.p(v1,0);
          augment.p(v1,v2)
          augment.p(v1 Sadd "0.4",v2);
          augment.p(v1 Sadd "0.4",0);
          gfill p--cycle withcolor .8white;
          gdraw p--cycle;
          );
endgraph;
\stopMPpage

...which gives bars of width 0.4 starting at abscissa 1 and 2 as expected. To increase the width of the bars to 0.8 and have them centered over 1 and 2, I expect to Ssub from the first two augments:

\usemodule[m-graph]
\startMPpage[instance=graph]
input sarith;
draw begingraph(5cm,5cm);
 gdata("data1", v,
          path p;
          augment.p(v1 Ssub "0.4",0);
          augment.p(v1 Ssub "0.4",v2);
          augment.p(v1 Sadd "0.4",v2);
          augment.p(v1 Sadd "0.4",0);
          gfill p--cycle withcolor .8white;
          gdraw p--cycle;
          );
endgraph;
\stopMPpage

However, the Ssub adds instead and gives a line at 1.4 and 2.4.

Compiling the above with mpost or mptopdf gives the desired result(s), but I am curious if this can be resolved so such bar graphs could be made within ConTeXT/METAFUN.

Thanks! John



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