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IDProjectCategoryView StatusDate SubmittedLast Update
0002301graphvizDotpublic2013-06-26 10:142013-06-26 10:51
Assigned Toellson 
StatusclosedResolutionno change required 
PlatformGNU/LinuxOSDebian GNU/LinuxOS VersionWheezy
Summary0002301: arrow results in syntax error
Description  graph {
    a -> b;

... results in:

Error: <stdin>:5: syntax error near line 5
context: a >>> - <<< > b;

However, when I replace "->" with "--" it works.
Steps To Reproducedot -Tpng -oout < with having the following content:
  graph {
    a -> b;
Additional InformationThis was my first step with dot. So it is freshly installed and not customized. Error is also reproducible when using dot within Emacs/Org-mode.
TagsNo tags attached.
VERSIONdot - graphviz version 2.26.3 (20100126.1600)
Attached Files

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-  Notes
User avatar (0000368)
ellson (administrator)
2013-06-26 10:25

" graph {"

You told it to expect an undirected graph, so the syntax requires that you provide undirected edges. Change this to " digraph {" to use directed edges.

Its all a bit of a historical artifact, IMO. It isn't actually possible to specify a truly undirected edge in a linear text form, since there is always an ordering of the ends in the linear text.

Basically, we could have used "--" everywhere. In fact you can do a considtent directed edge layout on an undirected "graph" exactly because of the assumed "tail--head" ordering.

At this point, it serves only to catch intent.

Arrows are really independent of direction, except for the default head arrow in directed graphs. You can override head and tail arrow decorations in both directed and undirected graphs.

- Issue History
Date Modified Username Field Change
2013-06-26 10:14 novoid New Issue
2013-06-26 10:25 ellson Note Added: 0000368
2013-06-26 10:51 erg Assigned To => ellson
2013-06-26 10:51 erg Status new => closed
2013-06-26 10:51 erg Resolution open => no change required

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