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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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5
doc/TutorialSlicingIndexing.dox
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@@ -15,7 +15,7 @@ All the aforementioned operations are handled through the generic DenseBase::ope
Each argument can be:
- An integer indexing a single row or column, including symbolic indices.
- The symbol Eigen::all representing the whole set of respective rows or columns in increasing order.
- An ArithmeticSequence as constructed by the Eigen::seq, Eigen::seqN, or Eigen::lastN functions.
- An ArithmeticSequence as constructed by the Eigen::seq, Eigen::seqN, or Eigen::placeholders::lastN functions.
- Any 1D vector/array of integers including %Eigen's vector/array, expressions, std::vector, std::array, as well as plain C arrays: `int[N]`.
More generally, it can accepts any object exposing the following two member functions:
@@ -114,7 +114,8 @@ Here are some examples for a 2D array/matrix \c A and a 1D array/vector \c v.
As seen in the last exemple, referencing the <i> last n </i> elements (or rows/columns) is a bit cumbersome to write.
This becomes even more tricky and error prone with a non-default increment.
Here comes \link Eigen::lastN(SizeType) Eigen::lastN(size) \endlink, and \link Eigen::lastN(SizeType,IncrType) Eigen::lastN(size,incr) \endlink:
Here comes \link Eigen::placeholders::lastN(SizeType) Eigen::placeholders::lastN(size) \endlink, and
\link Eigen::placeholders::lastN(SizeType,IncrType) Eigen::placeholders::lastN(size,incr) \endlink:
<table class="manual">
<tr>