Re: Graphical representations of syntax trees?

Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.com> writes:
>On 2/6/2022 10:32 PM, Anton Ertl wrote:
>> Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.com> writes:
>>> Are there any resources, or papers, about the subject of representing
>>> syntax trees graphically?
>>
>> There are LaTeX modes for displaying trees. There is also the
>> graphviz package for visualizing graphs.
>
>Sure, these are packages. But no actual algorithms, or discussions of
>how to do these things by myself.


Seems pretty trivial to me. If a rule


A: B C


is used for parsing a part of the input, you generate a node for this
rule (e.g., labeled "A"), with nodes for B and C as children. If you
want it to look nice, you arrange for all the terminals to be at the
same (geometrical, not logical) level. I think that's not very hard
with graphviz. Then you get trees like:


        E
      /|\
    F |F
  /|\||
  1*2+3


A web search for "bison dot files" resulted in
<https://www.gnu.org/software/bison/manual/html_node/Graphviz.html>,
but this describes a visual representation of the parser, not the
parse tree.


>[I suspect the practical problem is that for any but the tiniest programs
>the parse tree will be so large and bushy as to be unreadable. -John]


IIRC (only read about that part, and a long time ago) graphviz
contains a tool that supports folding/unfolding parts of the graph
interactively, exactly because of this problem.


- anton
--
M. Anton Ertl
anton@mips.complang.tuwien.ac.at
http://www.complang.tuwien.ac.at/anton/

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