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MathGroup Archive 2005

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Re: ! operator

  • To: mathgroup at
  • Subject: [mg55930] Re: ! operator
  • From: Jon Harrop <usenet at>
  • Date: Sun, 10 Apr 2005 23:07:06 -0400 (EDT)
  • References: <d3b18l$sgd$>
  • Sender: owner-wri-mathgroup at

DongGook Park wrote:
> This behaviour seems quite suspicious?

The "!" operator seems to do different things depending on whether it is
lexed at the front of a line (excluding whitespace), or parsed as a pre-
(Not) or post-fix (Factorial) operator. From the command-line MathKernel on
a Linux box:

In[1]:= !MemberQ[{1,2,3},3]
/bin/bash: line 1: MemberQ[1,3]: command not found

So it seems to be using the shell, bash, to execute something. Note that it
isn't executing quite what is was given though... :-)

Dr Jon D Harrop, Flying Frog Consultancy

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