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SyntaxInfo/Notebug bug?

• To: mathgroup at smc.vnet.net
• Subject: [mg110803] SyntaxInfo/Notebug bug?
• From: James Stein <mathgroup at stein.org>
• Date: Wed, 7 Jul 2010 07:42:40 -0400 (EDT)

No surprises if I execute this in a cell:

   ClearAll [ g ];
   SyntaxInformation [ g ]
   g [ x_] := x;
   g [ 3 ]


But if I now execute this in another cell:

   SyntaxInformation [ g ] = {"ArgumentsPattern" -> {_, _}};
   g [ 3 ]

   SyntaxInformation [ g ]

   ClearAll [ g ]
   g [ 3 ]

   SyntaxInformation [ g ]

the output will be as expected, but there is an ugly side effect:

In BOTH cells all calls "g [ 3 ]" now contain a red caret

following the "3", indicating a missing argument.

(I am using Mathematica 7.0.1 on Mac OS X 10.6.4, YMMV).


It seems to me that 'ClearAll' removes syntax information,

as I expected, but this removal is not communicated to the

Notebook front end.  My experience is that the kernel must be

restarted in order to remove the erroneous red caret.


Is this a bug in Mathematica, or in my (mis?)understanding of
SyntaxInformation?