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Re: Unacceptable bug in Mathematica

  • To: mathgroup at smc.vnet.net
  • Subject: [mg93538] Re: Unacceptable bug in Mathematica
  • From: "Steve Luttrell" <steve at _removemefirst_luttrell.org.uk>
  • Date: Thu, 13 Nov 2008 21:07:56 -0500 (EST)
  • References: <gfgqf2$dj0$1@smc.vnet.net>

Why do you think Exp[] is not syntactically correct? If you want a 
syntactically incorrect expression you could try Exp[ instead, where the 
missing ] causes it to be incomplete in a way that makes it syntactically 
incorrect.

Because Exp[] is a syntactically correct Mathematica expression the 
Mathematica kernel evaluates it, and produces the result Exp[] (i.e. no 
change), and simultaneously produces a warning message "Exp::argx: Exp 
called with 0 arguments; 1 argument is expected.".

If you override the default behaviour of Exp[], for instance by using

Unprotect[Exp];
Exp[] := myexp[];
Protect[Exp];

then Exp[] will evaluate to myexp[].

-- 
Stephen Luttrell
West Malvern, UK

"psycho_dad" <s.nesseris at gmail.com> wrote in message 
news:gfgqf2$dj0$1 at smc.vnet.net...
> The other day, a friend discovered something that may qualify as a
> major bug in Mathematica (tested in 6.0.3):
>
> SyntaxQ["Exp[]"]
>
> (notice that Exp has no argument) returns
>
> True !!!!
>
> According to the documentation:
>
> SyntaxQ["string"] returns True if the string corresponds to
> syntactically correct input for a single Mathematica expression, and
> returns False otherwise.
>
> At least for me Exp[] is not syntactically correct. I expected more
> from Mathematica...
>
> Cheers
> 



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