Re: Detecting and handling error messages?
- To: mathgroup at smc.vnet.net
- Subject: [mg24346] Re: Detecting and handling error messages?
- From: "Dale Horton" <daleh at wolfram.com>
- Date: Sun, 9 Jul 2000 04:52:51 -0400 (EDT)
- Organization: Wolfram Research, Inc.
- References: <8jrbto$dqe@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
The tricky part of using Check is that it doesn't check for messages that
are turned off.
So the question becomes, how do I leave a message on but prevent it from
getting printed.
Fortunately, there's a global variable that controls where these messages
are sent.
In[1]:=
?$Messages
"$Messages gives the list of files and pipes to which message output is
sent."
In[2]:=
$Messages
Out[2]=
{OutputStream["stdout", 1]}
We can use a Block to temporarily suspend the output of all messages.
In[3]:=
Block[{$Messages = {}},
Check[Sin[1, 2], Print["Try again!"]]
]
"Try again!"
-Dale
"AES" <siegman at stanford.edu> wrote in message
news:8jrbto$dqe at smc.vnet.net...
> What I'm really after is a simple way of detecting (testing) if errors
> have occurred during the execution of a given Input cell, so I can note
> this and maybe do something, but without actually having the error
> messages be printed to the screen.
>
> I note that The Mathematica Book on p. 1155 says
>
> Off[symbol::tag] switches off a message, SO THAT IT IS NO
> LONGER PRINTED (emphasis mine)
>
> Page 460 says
>
> $MessageList a list of the messages PRODUCED during
> a particular computation
>
> Note: "produced", not "printed" -- ??
>
> Page 1249 says
>
> $MessageList is a global variable that gives a list of the
> names of messages GENERATED during the evaluation of
> the current input line
>
> "Generated" ?=? "produced" ?=? "printed".
>
> Anyway, as best I can tell by trial and error, messages that have been
> Off[ ]'ed do not appear in $MessageList, and Check[ ] explicitly doesn't
> test for Off[ ]'ed messages. So is there a way to test if the
> associated errors have or have not occurred?
>
> Thanks siegman at stanford.edu
>