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xo-unit: bugfix: need handling for power=-1/2

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This commit is contained in:
Roland Conybeare 2024-05-04 14:50:58 -04:00
commit 9a5def616b
2 changed files with 21 additions and 11 deletions
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23
include/xo/unit/natural_unit.hpp
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@ -215,20 +215,29 @@ namespace xo {
bpu2_rescale(const bpu<Int> & orig,
const scalefactor_ratio_type & new_scalefactor)
{
/* we have orig, representing qty (b.u)^p,
* with b=orig.scalefactor, u=native dimension, p=orig.power
*/
ratio::ratio<Int> mult = (orig.scalefactor() / new_scalefactor);
/* inv: p_frac in [0, 1) */
/* inv: p_frac in (-1, 1) */
auto p_frac = orig.power().frac();
/* asof c++26: replace mult_sq with ::pow(mult, p_frac) */
double mult_sq = std::numeric_limits<double>::quiet_NaN();
if (p_frac.den() == 1) {
mult_sq = 1.0;
} else if(p_frac.den() == 2) {
mult_sq = mult.template convert_to<double>();
} else {
// remaining possibilities not supported until c++26
/* pre-c++26 workaround */
{
if (p_frac.den() == 1) {
mult_sq = 1.0;
} else if(p_frac.num() == 1 && p_frac.den() == 2) {
mult_sq = mult.template convert_to<double>();
} else if(p_frac.num() == -1 && p_frac.den() == 2) {
mult_sq = 1.0 / mult.template convert_to<double>();
} else {
// remaining possibilities not supported until c++26
}
}
ratio::ratio<Int> mult_p = mult.power(orig.power().floor());