Storing and retrieving

[Karl Hasselström]

On 2005-07-02 03:53:52 +0000, mrgrynch at comcast.net wrote:

> I have a need to preserve a bunch of GMP floating point values (from
> an array of mpf_class objects) for retrieval at a later time. The
> experiement I am running will take about a year, and I'd hate to
> lose it all if the power goes out, etc...
>
> I was thinking the easiest way to do this is with strings. Has
> anyone done this before? Reading through the documentation, I'm not
> entirely sure about the argument list to be passed to the functions
> which handle this, nor how they would work through the C++ class
> interface, which I am using. Would I have to extract a reference to
> the underlying C structure before converting to and from strings?

Hmm. For integers, there are nice binary I/O functions:
http://swox.com/gmp/manual/Integer-Import-and-Export.html. Doesn't
seem to be any such functions dealing with mpfs, though.

Formatted output in base 16 or 32 should be the second best thing.
http://swox.com/gmp/manual/C---Formatted-Output.html and
http://swox.com/gmp/manual/C---Formatted-Input.html explain how to do
formatted IO of mpfs. If they can't give you sufficient control of the
output format (I don't know if they do -- they seem to use the usual
C++ way of controlling such things, and I haven't touched C++ in
years), you can always use the C formatted IO functions -- again, see
the manual (the very first section in the C++ chapter explains how to
get mpf_t values out of mpf_class values).

-- 
Karl Hasselström, kha at treskal.com
      www.treskal.com/kalle
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