commit 1f374a9fe53e362ab76fb36e1dc53f6609991009
author Sergiu Deitsch <sergiu.deitsch@gmail.com> Sun Nov 21 15:26:45 2021 +0100
committer Sergiu Deitsch <sergiu.deitsch@gmail.com> Mon Nov 29 21:33:28 2021 +0100
tree 8ca1ef5f89d6afd7ea5f83fa7eb0ad1d121632bf
parent 06e68dbc5a0895ba18da8dc8123a845648108e33

Support promotion in comparison between Jet and scalars

Previously, Jet did not allow comparison between its value and a scalar
of another type. Specifically, the comparison was limited to scalars of
the same type effectively disabling standard promotion rules. Instead,
users would be required either to cast values to target Jet arithmetic
type or explicitly construct a Jet instance that can be eventually used
for comparison purposes.

However, such a behavior is not intuitive and causes problems with types
that rely on standard promotion rules (e.g., std::complex in some
implementations).

This changeset extends the comparison operators by enabling logical
comparisons between a Jet and values compatible to the underlying scalar
type (e.g., int). To be as generic as possible, the types allowed to be
passed to comparison operators are constrained using SFINAE. This in
turn allows a recursive expansion of jets and therefore the comparison
of a nested jets with a scalar.

The changes alleviate problems described in #414 and also allow the use
of special functions from Boost.Math, e.g., for computing the reciprocal
using boost::math::pow<-1>(...).

Change-Id: I3625791e6c8c2c0bfbffbbdb09e179a32e57f306