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Re: Transform list of numbers into pure functions using replace rule
*To*: mathgroup at smc.vnet.net
*Subject*: [mg89479] Re: Transform list of numbers into pure functions using replace rule
*From*: dh <dh at metrohm.ch>
*Date*: Tue, 10 Jun 2008 07:13:17 -0400 (EDT)
*References*: <g2lb8t$964$1@smc.vnet.net>
Hi Mac,
you have a mistake in the pattern, it should read: x_/;NumberQ[x] or
x?NumberQ. Then there is no need to convert to a string:
{1,2,f[x]}/.x_?NumberQ->Function[x]
or
{1,2,f[x]}/.x_?NumberQ->(x&)
hope this helps, Daniel
Mac wrote:
> Hello,
>
> I'm developed a program to invert satellite observations into
> geophysical variables such as forest biomass. One of the input
> parameters are the errors in the observation channels which can be
> either constant or a function. To be consistent the program expects
> all errors to be functions but they can also be constant functions
> e.g. if the error is 4 then the input parameter is "4&".
>
> I've however hit a problem with the replacement rule that allows me to
> transform all input errors into a function. The following works as
> expected in that constants in the list are transformed into virtual
> functions and functions in the list are left alone.
>
> In[40]:= If[NumberQ[#], ToExpression[ToString[#] <> "&"], #] & /@ {1,
> 2, 3 &, f[x]}
>
> Out[40]= {1 &, 2 &, 3 &, f[x]}
>
> However, I cannot find a replacement rule to do the same job. Here is
> one try:
>
> In[39]:= {1, 2, f[x]} /. x_ /; NumberQ -> Hold[x &]
>
> Out[39]= {1, 2, f[x]}
>
> Any help would be appreciated.
>
> Mac
>
>
--
Daniel Huber
Metrohm Ltd.
Oberdorfstr. 68
CH-9100 Herisau
Tel. +41 71 353 8585, Fax +41 71 353 8907
E-Mail:<mailto:dh at metrohm.com>
Internet:<http://www.metrohm.com>
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