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Move Eigen::all,last,lastp1,lastN to Eigen::placeholders::.

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These names are so common, IMO they should not exist directly in the
`Eigen::` namespace.  This prevents us from using the `last` or `all`
names for any parameters or local variables, otherwise spitting out
warnings about shadowing or hiding the global values.  Many external
projects (and our own examples) also heavily use
```
using namespace Eigen;
```
which means these conflict with external libraries as well, e.g.
`std::fill(first,last,value)`.

It seems originally these were placed in a separate namespace
`Eigen::placeholders`, which has since been deprecated.  I propose
to un-deprecate this, and restore the original locations.

These symbols are also imported into `Eigen::indexing`, which
additionally imports `fix` and `seq`. An alternative is to remove the
`placeholders` namespace and stick with `indexing`.

NOTE: this is an API-breaking change.

Fixes #2321.
This commit is contained in:
Antonio Sanchez
2021-09-15 14:10:29 -07:00
parent 44da7a3b9d
commit 5dac0b53c9
10 changed files with 83 additions and 57 deletions
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77
Eigen/src/Core/util/IndexedViewHelper.h
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@@ -17,7 +17,11 @@ namespace Eigen {
namespace internal {
struct symbolic_last_tag {};
}
} // namespace internal
namespace placeholders {
typedef symbolic::SymbolExpr<internal::symbolic_last_tag> last_t;
/** \var last
* \ingroup Core_Module
@@ -30,38 +34,20 @@ struct symbolic_last_tag {};
* A typical usage example would be:
* \code
* using namespace Eigen;
* using Eigen::last;
* using Eigen::placeholders::last;
* VectorXd v(n);
* v(seq(2,last-2)).setOnes();
* \endcode
*
* \sa end
*/
static const symbolic::SymbolExpr<internal::symbolic_last_tag> last; // PLEASE use Eigen::last instead of Eigen::placeholders::last
static const last_t last;
/** \var lastp1
* \ingroup Core_Module
*
* Can be used as a parameter to Eigen::seq and Eigen::seqN functions to symbolically
* reference the last+1 element/row/columns of the underlying vector or matrix once
* passed to DenseBase::operator()(const RowIndices&, const ColIndices&).
*
* This symbolic placeholder supports standard arithmetic operations.
* It is essentially an alias to last+fix<1>.
*
* \sa last
*/
#ifdef EIGEN_PARSED_BY_DOXYGEN
static const auto lastp1 = last+fix<1>;
#else
// Using a FixedExpr<1> expression is important here to make sure the compiler
// can fully optimize the computation starting indices with zero overhead.
static const symbolic::AddExpr<symbolic::SymbolExpr<internal::symbolic_last_tag>,symbolic::ValueExpr<Eigen::internal::FixedInt<1> > > lastp1(last+fix<1>());
#endif
} // namespace placeholders
namespace internal {
// Replace symbolic last/end "keywords" by their true runtime value
// Replace symbolic last/end "keywords" by their true runtime value
inline Index eval_expr_given_size(Index x, Index /* size */) { return x; }
template<int N>
@@ -70,7 +56,7 @@ FixedInt<N> eval_expr_given_size(FixedInt<N> x, Index /*size*/) { return x; }
template<typename Derived>
Index eval_expr_given_size(const symbolic::BaseExpr<Derived> &x, Index size)
{
return x.derived().eval(last=size-1);
return x.derived().eval(Eigen::placeholders::last=size-1);
}
// Extract increment/step at compile time
@@ -165,23 +151,44 @@ template<int Size> struct get_compile_time_incr<AllRange<Size> > {
} // end namespace internal
namespace placeholders {
typedef symbolic::AddExpr<symbolic::SymbolExpr<internal::symbolic_last_tag>,symbolic::ValueExpr<Eigen::internal::FixedInt<1> > > lastp1_t;
typedef Eigen::internal::all_t all_t;
/** \var lastp1
* \ingroup Core_Module
*
* Can be used as a parameter to Eigen::seq and Eigen::seqN functions to symbolically
* reference the last+1 element/row/columns of the underlying vector or matrix once
* passed to DenseBase::operator()(const RowIndices&, const ColIndices&).
*
* This symbolic placeholder supports standard arithmetic operations.
* It is essentially an alias to last+fix<1>.
*
* \sa last
*/
#ifdef EIGEN_PARSED_BY_DOXYGEN
static const auto lastp1 = last+fix<1>;
#else
// Using a FixedExpr<1> expression is important here to make sure the compiler
// can fully optimize the computation starting indices with zero overhead.
static const lastp1_t lastp1(last+fix<1>());
#endif
/** \var end
* \ingroup Core_Module
* \sa lastp1
*/
static const lastp1_t end = lastp1;
/** \var all
* \ingroup Core_Module
* Can be used as a parameter to DenseBase::operator()(const RowIndices&, const ColIndices&) to index all rows or columns
*/
static const Eigen::internal::all_t all; // PLEASE use Eigen::all instead of Eigen::placeholders::all
static const Eigen::internal::all_t all;
namespace placeholders {
typedef symbolic::SymbolExpr<internal::symbolic_last_tag> last_t;
typedef symbolic::AddExpr<symbolic::SymbolExpr<internal::symbolic_last_tag>,symbolic::ValueExpr<Eigen::internal::FixedInt<1> > > end_t;
typedef Eigen::internal::all_t all_t;
EIGEN_DEPRECATED static const all_t all = Eigen::all; // PLEASE use Eigen::all instead of Eigen::placeholders::all
EIGEN_DEPRECATED static const last_t last = Eigen::last; // PLEASE use Eigen::last instead of Eigen::placeholders::last
EIGEN_DEPRECATED static const end_t end = Eigen::lastp1; // PLEASE use Eigen::lastp1 instead of Eigen::placeholders::end
}
} // namespace placeholders
} // end namespace Eigen