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MathGroup Archive 2006

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Re: question about Block

  • To: mathgroup at smc.vnet.net
  • Subject: [mg69788] Re: question about Block
  • From: dimmechan at yahoo.com
  • Date: Sat, 23 Sep 2006 04:44:20 -0400 (EDT)
  • References: <eeqpqm$oel$1@smc.vnet.net><eetv8f$9uk$1@smc.vnet.net>

Dear Jens,

Because maybe I was not very clear, I will state gain my question.
Both of the following commands fail to prevent the presence of the
NIntegrate::inum message.
Can you understand why?

lst={1/x,1/x^2};

Block[{Message}, NIntegrate[lst, {x, 1, 2}]]
\!\(NIntegrate::"inum" : "Integrand \!\({1\/x,
     1\/x\^2}\) is not numerical at \!\({x}\) = {1.5`}."\)
NIntegrate[lst, {x, 1, 2}]

Block[{$Messages = {}}, NIntegrate[lst, {x, 1, 2}]]
\!\(NIntegrate::"inum" : "Integrand \!\({1\/x,
     1\/x\^2}\) is not numerical at \!\({x}\) = {1.5`}."\)
NIntegrate[lst, {x, 1, 2}]

Thanks


Î?/Î? Jens-Peer Kuska έγÏ?αÏ?ε:
> Hi,
>
> since there is no function, that tell you the
> answer to the question
> is message func::xyz On or Off you can't switch
> off
> the message in your functions, because you will
> change a global
> state. So, if you wish to turn off the messages
> inside of your
> function but don't change the global state you
> have to use
> the Block[{Message},..] construction.
>
> Regards
>   Jens
>
> <dimmechan at yahoo.com> schrieb im Newsbeitrag
> news:eeqpqm$oel$1 at smc.vnet.net...
> | Hello to all.
> |
> | Block as it is well known to the members of this
> forum does have some
> | nice applications.
> | For example
> |
> | $Version
> | "5.2 for Microsoft Windows (June 20, 2005)"
> |
> | Block[{Message}, Integrate[1/x, {x, -1, 2}]]
> | Infinity
> | Block[{Message}, NIntegrate[Sin[x]/x, {x, 0,
> Infinity}]]
> | 2.6457805920701
> |
> | (execute the commands without Block to see the
> messages)
> |
> | Let me now define a list of two functions.
> |
> | lst = {1/x, 1/x^2};
> |
> | Then
> |
> | NIntegrate[lst, {x, 1, 2}]
> | \!\(NIntegrate::"inum" : "Integrand \!\({1\/x,
> |     1\/x\^2}\) is not numerical at \!\({x}\) =
> {1.5`}."\)
> | NIntegrate[lst, {x, 1, 2}]
> |
> | because NIntegrate has the attribute HoldAll
> |
> | Attributes[NIntegrate]
> | {HoldAll, Protected}
> |
> | Of course
> |
> | NIntegrate[Evaluate[lst], {x, 1, 2}]
> | {0.693147180559947, 0.5000000000000211}
> |
> | Now to my surprise I discovered that the
> following commands fail to
> | prevent the appearance of  NIntegrate::inum
> message.
> |
> | Block[{Message}, NIntegrate[lst, {x, 1, 2}]]
> | \!\(NIntegrate::"inum" : "Integrand \!\({1\/x,
> |     1\/x\^2}\) is not numerical at \!\({x}\) =
> {1.5`}."\)
> | NIntegrate[lst, {x, 1, 2}]
> |
> | Block[{$Messages = {}}, NIntegrate[lst, {x, 1,
> 2}]]
> | \!\(NIntegrate::"inum" : "Integrand \!\({1\/x,
> |     1\/x\^2}\) is not numerical at \!\({x}\) =
> {1.5`}."\)
> | NIntegrate[lst, {x, 1, 2}]
> |
> | What is more strange is that the relevant
> Plot::plnr message can be
> | prevented.
> |
> | Plot[lst, {x, 1, 2}, DisplayFunction ->
> Identity];
> | Plot::plnr : lst is not a machine-size real
> number at x =
> | 1.0000000416666666`. (...3 times...)
> | General::stop : Further output of Plot::plnr
> will be suppressed during
> | this \
> | calculation.
> |
> | Attributes[Plot]
> | {HoldAll, Protected}
> |
> | Block[{Message}, Plot[lst, {x, 1, 2},
> DisplayFunction -> Identity]];
> | Block[{$Messages = {}}, Plot[lst, {x, 1, 2},
> DisplayFunction ->
> | Identity]];
> |
> | Of course someone can simply switch off the
> message.
> |
> | Off[NIntegrate::inum]
> | NIntegrate[lst, {x, 1, 2}]
> | NIntegrate[lst, {x, 1, 2}]
> |
> | On[NIntegrate::inum]
> |
> | but the question remains why exist this strange
> (at least for me)
> | situation.
> |
> | Any comments/suggestions?
> |
> | Dimitris
> |


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