ENH: UList iterators at offset from begin

- simplifies addressing within sub-ranges.
  Clamps the access range directly

applications/test/List/Test-List.C

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2017-2021 OpenCFD Ltd.
+    Copyright (C) 2017-2023 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -365,6 +365,12 @@ int main(int argc, char *argv[])
             Info<<"assigned identity in range:" << subset
                 << "=> " << flatOutput(longLabelList) << nl;
 
+            // Assign values in iterator range
+            std::iota(longLabelList.begin(15), longLabelList.begin(50), 115);
+
+            Info<<"assigned values in iterator range "
+                << "=> " << flatOutput(longLabelList) << nl;
+
             labelList someList(identity(24));
 
             longLabelList.slice(subset) =
@@ -410,8 +416,20 @@ int main(int argc, char *argv[])
         longLabelList.slice({5,-5}) = 42;
         longLabelList.slice({21,100}) = 42;
 
-        //Good: does not compile
-        longLabelList.slice(labelRange(20,50)) = constLabelList;
+        #if 0
+        // Compiles, but is runtime abort!
+        const bool oldThrowingError = FatalError.throwing(true);
+        try
+        {
+            longLabelList.slice(labelRange(20,50)) = constLabelList;
+        }
+        catch (const Foam::error& err)
+        {
+            Info<< "Caught FatalError "
+                << err << nl << endl;
+        }
+        FatalError.throwing(oldThrowingError);
+        #endif
 
         //Good: does not compile
         // longLabelList[labelRange(20,50)] = fixedLabelList;

src/OpenFOAM/containers/Lists/List/UList.C

@@ -261,24 +261,28 @@ Foam::label Foam::UList<T>::rfind(const T& val, label pos) const
 template<class T>
 bool Foam::UList<T>::operator==(const UList<T>& list) const
 {
+    /// OR:
+    /// return
+    /// (
+    ///     (this->size_ == list.size_)
+    //   && std::equal(cbegin(), cend(), list.cbegin())
+    /// );
+
     const label len = this->size_;
     if (len != list.size_)
     {
         return false;
     }
 
-    bool equal = true;
-
     List_CONST_ACCESS(T, (*this), lhs);
     List_CONST_ACCESS(T, (list), rhs);
 
     for (label i = 0; i < len; ++i)
     {
-        equal = (lhs[i] == rhs[i]);
-        if (!equal) break;
+        if (!(lhs[i] == rhs[i])) return false;
     }
 
-    return equal;
+    return true;
 }
 
 
@@ -292,11 +296,21 @@ bool Foam::UList<T>::operator!=(const UList<T>& list) const
 template<class T>
 bool Foam::UList<T>::operator<(const UList<T>& list) const
 {
+    /// OR:
+    /// return std::lexicographical_compare
+    /// (
+    ///     cbegin(), cend(),
+    ///     list.cbegin(), list.cend()
+    /// );
+
+    const const_iterator last1 = cend();
+    const const_iterator last2 = list.cend();
+
     for
     (
-        const_iterator lhs = begin(), rhs = list.begin();
-        lhs < end() && rhs < list.end();
-        ++lhs, ++rhs
+        const_iterator lhs = cbegin(), rhs = list.cbegin();
+        (lhs != last1) && (rhs != last2);
+        ++lhs, (void) ++rhs
     )
     {
         if (*lhs < *rhs)

src/OpenFOAM/containers/Lists/List/UList.H

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2017-2021 OpenCFD Ltd.
+    Copyright (C) 2017-2023 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -407,6 +407,10 @@ public:
         //- Return an iterator to end traversing the UList
         inline iterator end() noexcept;
 
+        //- Return iterator at offset i from begin,
+        //- clamped to [0,size] range
+        inline iterator begin(const label i) noexcept;
+
 
     // Random access iterator (const)
 
@@ -422,6 +426,14 @@ public:
         //- Return const_iterator to end traversing the constant UList
         inline const_iterator end() const noexcept;
 
+        //- Return const_iterator at offset i from begin,
+        //- clamped to [0,size] range
+        inline const_iterator cbegin(const label i) const noexcept;
+
+        //- Return const_iterator at offset i from begin,
+        //- clamped to [0,size] range
+        inline const_iterator begin(const label i) const noexcept;
+
 
     // Reverse iterators (non-const)
 

src/OpenFOAM/containers/Lists/List/UListI.H

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2015-2021 OpenCFD Ltd.
+    Copyright (C) 2015-2023 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -345,6 +345,29 @@ Foam::UList<T>::cbegin() const noexcept
     return v_;
 }
 
+
+template<class T>
+inline typename Foam::UList<T>::iterator
+Foam::UList<T>::begin(const label i) noexcept
+{
+    return (v_ + (i < 0 ? 0 : size_ < i ? size_ : i));
+}
+
+template<class T>
+inline typename Foam::UList<T>::const_iterator
+Foam::UList<T>::begin(const label i) const noexcept
+{
+    return (v_ + (i < 0 ? 0 : size_ < i ? size_ : i));
+}
+
+template<class T>
+inline typename Foam::UList<T>::const_iterator
+Foam::UList<T>::cbegin(const label i) const noexcept
+{
+    return (v_ + (i < 0 ? 0 : size_ < i ? size_ : i));
+}
+
+
 template<class T>
 inline typename Foam::UList<T>::iterator
 Foam::UList<T>::end() noexcept

src/OpenFOAM/containers/Lists/List/stdVectorIO.C

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2019 OpenCFD Ltd.
+    Copyright (C) 2019-2023 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -46,7 +46,7 @@ Foam::Ostream& Foam::operator<<(Ostream& os, const std::vector<T>& list)
     {
         os << *iter;
 
-        for (++iter; iter != last; ++iter)
+        while (++iter != last)
         {
             os << token::SPACE << *iter;
         }