The Universe of Discourse

Linogram development: 20061226 Update
I have made significant progress on the "arrays" feature. I recognized that it was actually three features; I have two of them implemented now. Taking the example from further down the page:

        define regular_polygon[N] closed {
          param number radius, rotation=0;
          point vertex[N], center;
          line  edge[N];
          constraints {
            vertex[i] = center + radius * cis(rotation + 360*i/N);
            edge[i].start = vertex[i];
            edge[i].end   =  vertex[i+1];
          }
        }

The following example works just fine:

        number p[3];
        number q[3];
        constraints {
          p[i] = q[i];
          q[i] = i*2;
        }

        number p[3];
        number q[3];
        constraints {
          p[i] = q[i+1];
        }

p₀ = q₁
p₁ = q₂
p₂ = q₃

The third of these is defective, because there is no q₃. If the figure is "closed" (which is the default) the subscripts should wrap around, turning the defective constraint into p₂ = q₀ instead. If the figure is declared "open", the defective constraint should simply be discarded.

The syntax for parameterized definitions (define regular_polygon[N] { ... }) is still a bit up in the air; I am now leaning toward a syntax that looks more like define regular_polygon { param index N; ... } instead.

The current work on the "arrays" feature is in the CVS repository on the branch arrays; get the version tagged tests-pass to get the most recent working version. Most of the interesting work has been on the files lib/Chunk.pm and lib/Expression.pm.

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