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Re: A riddle: Functions that return unevaluated when they cannot

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  • Subject: [mg82716] Re: A riddle: Functions that return unevaluated when they cannot
  • From: Albert <awnl at arcor.net>
  • Date: Tue, 30 Oct 2007 03:16:19 -0500 (EST)
  • References: <ff9sin$5vc$1@smc.vnet.net> <ffckoe$sop$1@smc.vnet.net> <ffed3p$bg7$1@smc.vnet.net> <ffhqss$4mr$1@smc.vnet.net> <fg4d62$681$1@smc.vnet.net>

Szabolcs Horv=C3=A1t wrote:
> Albert wrote:
>> Hi,
>>
>> Is this what you are looking for?
>
> Yes, it it.  Thank you!  My newsreader has misplaced your message, so I=

> did not notice it until now.
>
> A function like
> g[x_] := Module[{res}, Pause[3]; res = x + 2; res /; res < 10]
> reproduces the timing behaviour of Integrate[] et al. :-)  I was not
> familiar with this use of /; (it is described in the doc page of Module=
,
> not in the doc page of Condition)

ah, now I know that it is at least documented somewhere, also to my
understanding it is not clear from the docpage (and also not from the
examples or the old documentation in version 5) what exactly it does.
Strange. But well, it works and seems to stay there... And for
completeness: With and Block have the same part in their docpages.

albert



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