in reply to Converting Math::MPFR to Math::GMPq

So far, I tried converting Math::MPFR to Math::GMPf, then Math::GMPf to Math::GMPq, which works correctly

I think that's about the best you can do - ie, I can't spot anything better.
The mpfr library provides direct conversion to mpf_t and mpz_t types (using the mpfr_get_f and mpfr_get_z functions), but the mpfr_get_q function is not there - and hence no Rmpfr_get_q function in Math::MPFR.

It would be nice to avoid the overhead of having to load Math::GMPf but, other than that, I think your conversion should be working quite efficiently.

For 128 bits of precision, the value of the mpfr_t and mpf_t will be exactly equivalent, and the final mpq_t will be an exact representation of that floating point value.

Belated update: That last statement of mine is poorly thought out - the value of the mpfr_t and mpf_t will be exactly equivalent if the precision allocated to the mpfr_t equals the precision allocated to the mpf_t (irrespective of whether the precision is 128 or not).

Cheers,
Rob
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Re^2: Converting Math::MPFR to Math::GMPq
by trizen (Hermit) on Dec 28, 2015 at 14:05 UTC

    Thank you very much, Rob, for your reply and also for the Math::* modules.

    Definitely, would be nice to avoid the overhead of loading Math::GMPf, as I'm using it only in one place to do this particular conversion, but, nevertheless, I can live with that. :)

    All the best,
    Daniel

[reply]
      would be nice to avoid the overhead of loading Math::GMPf

      Thinking a bit more about it, it's no big deal to include an Rmpfr_get_q() XSub in Math::MPFR that does the mpfr_t to mpf_t to mpq_t conversion, and thereby avoids the need to load Math::GMPf.

      That function will be in the next release of Math::MPFR.
      I'm not sure when that will be - I could send you a patch against current (Math-MPFR-3.28) if you don't want to wait for 3.29.

      Cheers,
      Rob
[reply]

        That's awesome. Thank you very much, Rob. I'm looking forward to the next version.

        All the best,
        Daniel

[reply]

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