tree (sequence) diagram in Asymptote

Question

I want to draw tree diagram with Asymptote. But have some problems.

I searched and found 2 hints on the web. http://asymptote.sourceforge.net/FAQ/section4.html http://asymptote.sourceforge.net/doc/Frames-and-pictures.html

Using theese tips, and tried to box and trees.

settings.outformat="pdf";
unitsize(5cm);

usepackage(amsmath);

frame f1;
label(f1, "$\mathbb{N} \models A(0)$", Draw);
add(f1, (0, 5))

frame f2;
label(f2, "$\mathbb{N} \models A(1)$", Draw);
add(f2, (0, 4));

draw(f1 -- f2);

But this doesn't work. Last draw(f1 -- f2); command is wrong.

draw commands need coordinate. But this method is... not smart (for me).

I want to connect 2 boxes. How Can I connect 2 objects?

I found drawtree module in the official tutorials PDF, but it looks difficult to use flexibly(is tree's shape changeable?).

If there is a way of easily using drawtree module, would you tell that?

Thanks.

Answer 1

The following code works as a standalone asymptote script. I haven't used the drawtree module so I can't help you with that. In my code, I am not using frames. Instead, each label is drawn in the default picture.

texpreamble("\usepackage{amssymb}");
settings.outformat="pdf";
unitsize(5cm);

pair p1 = (0, 5);
pair p2 = (0, 4);

draw(p1--p2);

label("$\mathbb{N} \models A(0)$", p1, FillDraw(white, black));
label("$\mathbb{N} \models A(1)$", p2, FillDraw(white, black));

Answer 2

Since alternative methodologies are generally acceptable, I cannot resist providing a forest solution.

math content puts the content of all nodes in maths mode, avoiding the need for $...$. draw draws a border around each node in the tree.

The nodes are automatically connected: parent to child for each parent-child relationship. (Use <node content>, no edge for exceptions.) I've specified l sep to match the unit defined in the original code. This is the minimum distance between levels of the tree. (5cm is a lot.)

forest does not need explicit coordinates. It will automatically format the tree.

\documentclass[tikz, border=10pt, multi]{standalone}
\usepackage{forest,amssymb}
\begin{document}
\begin{forest}
  for tree={
    draw,
    math content,
    l sep=50mm,
  }
  [\mathbb{N} \models A(0)
    [\mathbb{N} \models A(1)]
  ]
\end{forest}
\end{document}

To alter the appearance of the tree is very easy. You just alter the preamble of the forest environment.

For example,

   for tree={
    draw=red,
    thick,
    edge={blue, thick, <->},
    fill=red!10,
    math content,
    l sep=50mm,
    grow=45,
  }

produces

while the specification for the tree itself remains identical

  [\mathbb{N} \models A(0)
    [\mathbb{N} \models A(1)]
  ]