- To: mathgroup at yoda.ncsa.uiuc.edu
- Subject: SetPrecision
- From: uunet!yoda.ncsa.uiuc.edu!keiper%wri (Jerry Keiper)
- Date: Mon, 2 Apr 90 17:24:41 CDT
Jeffrey P. Golden <uiucuxc!ALLEGHENY.SCRC.Symbolics.COM!jpg> writes:
>If the user types SetPrecision[1.2,30], I think it is pretty clear
>that most users mean the same number that SetPrecision[12/10,30]
>would mean, i.e. fill in with decimal 0's, which is not what
Since that sort of functionality is in general impossible, I presume that
the suggestion is only intended to make it more convenient to enter
numbers precisely. But the 1.2 will have been converted to 1.001100110011...
long before SetPrecision ever even gets to look at it. If the above
functionality is desired one can do something like
HighPrecision[x_, n_] := SetPrecision[Rationalize[x], n]
In:= SetPrecision[%, 60]
But this will only work for numbers that are essentially rational numbers
with relatively small denominators with a small rounding error thrown in
to allow it to be represented in binary.
I do not think that overloading SetPrecision to have this functionality
keiper at wri.com
Wolfram Research Inc.
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