Re: Transform list of numbers into pure functions using replace rule

*To*: mathgroup at smc.vnet.net*Subject*: [mg89487] Re: Transform list of numbers into pure functions using replace rule*From*: Mac <mwjdavidson at googlemail.com>*Date*: Tue, 10 Jun 2008 07:14:47 -0400 (EDT)*References*: <g2lb8t$964$1@smc.vnet.net>

On Jun 10, 9:42 am, Mac <mwjdavid... at googlemail.com> 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 Hello, Many thanks for your very quick reply. Your solution doesn't quite work because I would also like to transform lists of this type (it was in the first example I gave): In[3]:= {1, 2, f[x], 3 &} /. x_ /; NumberQ[x] -> (x &) Out[3]= {1 &, 2 &, f[x], 3 & &} The problem is the "3&&" which I would like to be "3&". Any magic that you can propose ? many thanks in any case Mac