Re: Graphical representations of syntax trees?

From	anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups	comp.compilers
Subject	Re: Graphical representations of syntax trees?
Date	2022-02-07 18:33 +0000
Organization	Institut fuer Computersprachen, Technische Universitaet Wien
Message-ID	<22-02-009@comp.compilers> (permalink)
References	<22-02-004@comp.compilers> <22-02-006@comp.compilers> <22-02-008@comp.compilers>

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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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Graphical representations of syntax trees? Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.com> - 2022-02-04 20:20 +0000
  Re: Graphical representations of syntax trees? gah4 <gah4@u.washington.edu> - 2022-02-06 13:07 -0800
    Re: Graphical representations of syntax trees? Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2022-02-06 23:38 +0100
    Re: Graphical representations of syntax trees? Steve Limb <stephenjohnlimb@gmail.com> - 2022-02-08 09:14 +0000
  Re: Graphical representations of syntax trees? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2022-02-06 22:32 +0000
    Re: Graphical representations of syntax trees? Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.com> - 2022-02-07 10:49 +0000
      Re: Graphical representations of syntax trees? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2022-02-07 18:33 +0000
      Re: Graphical representations of syntax trees? Jonathan Thornburg <jonathan@gold.bkis-orchard.net> - 2022-02-08 21:34 +0000
        Re: Graphical representations of syntax trees? Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2022-02-11 21:16 +0000
  Re: Graphical representations of syntax trees? "Alexei A. Frounze" <alexfrunews@gmail.com> - 2022-02-07 18:17 -0800

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