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MathGroup Archive 2012

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Re: How to call 'Clear' from within a function?


I thank all the responders for helping me to clarify my thoughts on this issue.

The reason I was using Strings, not Symbols, is too complicated and
too uninteresting to detail here.

To answer Albert Retey's question, what I was trying to do: I was
planning to investigate how precision affected certain computations.
It was my intention to set (and reset) various variables by calling a
single function which would repeatedly call a function such as this
one:

ClearAll [ f, x, watt, meter ];
SetAttributes [ f, HoldFirst ];
f [ var_, expr_, precision_, units_: 1 ] := (
   ClearAll [ var ];
   var = If [ precision == 0, expr,
      SetPrecision [ expr, precision ] ] units );

(* examine f: *)
f [ x, 5., 0 ]
f [ x, 5., 8 ]
f [ x, 5., 12, watt meter ^ -2 ]

As usual, an urge to increase precision turned moot with a more clever
algorithm.



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