On 01/07/18 21:20 +0200, François Dumont wrote:
Here is a new proposal between yours and mine.
It is still adding a function to wrap what __niter_base unwrap, I
called it __nwrap_iter for this reason. But it takes advantage of
Since "niter" refers to __normal_iterator I think a name based on
"niter" would be better than nsomething_iter.
__niter_wrap
__niter_rewrap
__niter_lift (misuse of functional programming term?)
__niter_raise (misuse of linear algebra term?)
__make_niter
__remake_niter
knowing that __niter_base will only unwrap random access iterator to
use an expression to that will do the right thing, no matter the
original iterator type.
OK, since __niter_base only transforms types based on
__normal_iterator that seems safe to assume (in theory we could use
__normal_iterator with non-random access iterators, but we don't).
Could you please add a comment to the __nwrap_iter saying something
like:
// Reverse the __niter_base transformation to get a
// __normal_iterator back again (this assumes that __normal_iterator
// is only used to wrap random access iterators, like pointers).
I eventually found no issue in the testsuite, despite the
std::equal change. I might have had a local invalid test.
Yes, I *did* test it already :-)
diff --git a/libstdc++-v3/include/bits/stl_algobase.h
b/libstdc++-v3/include/bits/stl_algobase.h
index d429943..003ae8d 100644
--- a/libstdc++-v3/include/bits/stl_algobase.h
+++ b/libstdc++-v3/include/bits/stl_algobase.h
@@ -277,6 +277,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__niter_base(_Iterator __it)
{ return __it; }
+ // Convert an iterator of type _From to an iterator of type _To.
+ // e.g. from int* to __normal_iterator<int*, Seq>.
+ template<typename _Iterator>
+ inline _Iterator
+ __nwrap_iter(_Iterator, _Iterator, _Iterator __res)
+ { return __res; }
+
+ template<typename _From, typename _To>
+ inline _From
+ __nwrap_iter(_From __from, _To __to, _To __res)
+ { return __from + (__res - __to); }
Every time you call this function you pass it:
__nwrap_iter(x, __niter_base(x), y)
So can the __niter_base(x) call happen inside __nwrap_iter?
i.e.
template<typename _From, typename _To>
inline _From
__nwrap_iter(_From __from, _To __res)
{ return __from + (__res - __niter_base(__from)); }
