ENH: new/revised emplace_back() [for DynamicList/List/PtrDynList/PtrList]

- returns reference as per C++17 std::vector

STYLE: drop unused, redundant DynamicField remove() method

src/OpenFOAM/containers/Lists/DynamicList/DynamicList.H

@@ -259,6 +259,11 @@ public:
         template<int AnySizeMin>
         inline void transfer(DynamicList<T, AnySizeMin>& list);
 
+        //- Construct an element at the end of the list,
+        //- return reference to the new list element
+        template<class... Args>
+        inline T& emplace_back(Args&&... args);
+
         //- Copy append an element to the end of this list.
         inline void push_back(const T& val);
 

src/OpenFOAM/containers/Lists/DynamicList/DynamicListI.H

@@ -503,6 +503,23 @@ Foam::DynamicList<T, SizeMin>::transfer
 }
 
 
+template<class T, int SizeMin>
+template<class... Args>
+inline T& Foam::DynamicList<T, SizeMin>::emplace_back(Args&&... args)
+{
+    // This could/should be better with inplace construction
+    // (as per std::vector), but currently lacking the methods for that
+    // so resize and move assign
+
+    const label idx = List<T>::size();
+    resize(idx + 1);
+
+    // move assign element
+    this->operator[](idx) = T(std::forward<Args>(args)...);
+    return this->back();
+}
+
+
 template<class T, int SizeMin>
 inline void Foam::DynamicList<T, SizeMin>::push_back
 (

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

@@ -240,6 +240,12 @@ public:
 
     // Edit
 
+        //- Construct an element at the end of the list,
+        //- return reference to the new list element.
+        //  If this is frequently required, consider a DynamicList instead.
+        template<class... Args>
+        inline T& emplace_back(Args&&... args);
+
         //- Append an element at the end of the list
         //  If this is frequently required, consider a DynamicList
         inline void push_back(const T& val);

src/OpenFOAM/containers/Lists/List/ListI.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.
@@ -171,6 +171,23 @@ inline T& Foam::List<T>::newElmt(const label i)
 }
 
 
+template<class T>
+template<class... Args>
+inline T& Foam::List<T>::emplace_back(Args&&... args)
+{
+    // This could/should be better with inplace construction
+    // (as per std::vector), but currently lacking the methods for that
+    // so resize and move assign
+
+    const label idx = this->size();
+    resize(idx + 1);
+
+    // move assign element
+    this->operator[](idx) = T(std::forward<Args>(args)...);
+    return this->back();
+}
+
+
 template<class T>
 inline void Foam::List<T>::push_back(const T& val)
 {

src/OpenFOAM/containers/PtrLists/PtrDynList/PtrDynList.H

@@ -141,9 +141,10 @@ public:
         template<int AnySizeMin>
         inline void swap(PtrDynList<T, AnySizeMin>& other);
 
-        //- Construct an element at the end of the list
+        //- Construct an element at the end of the list,
+        //- return reference to the new list element
         template<class... Args>
-        inline void emplace_back(Args&&... args);
+        inline T& emplace_back(Args&&... args);
 
         //- Append an element to the end of the list
         inline void push_back(T* ptr);

src/OpenFOAM/containers/PtrLists/PtrDynList/PtrDynListI.H

@@ -218,9 +218,10 @@ inline void Foam::PtrDynList<T, SizeMin>::swap
 
 template<class T, int SizeMin>
 template<class... Args>
-inline void Foam::PtrDynList<T, SizeMin>::emplace_back(Args&&... args)
+inline T& Foam::PtrDynList<T, SizeMin>::emplace_back(Args&&... args)
 {
     this->push_back(new T(std::forward<Args>(args)...));
+    return this->back();
 }
 
 

src/OpenFOAM/containers/PtrLists/PtrList/PtrList.H

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2018-2022 OpenCFD Ltd.
+    Copyright (C) 2018-2023 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -149,9 +149,10 @@ public:
         //- Same as resize()
         void setSize(const label newLen) { this->resize(newLen); }
 
-        //- Construct and append an element to the end of the list
+        //- Construct and append an element to the end of the list,
+        //- return reference to the new list element
         template<class... Args>
-        inline void emplace_back(Args&&... args);
+        inline T& emplace_back(Args&&... args);
 
         //- Append an element to the end of the list
         inline void push_back(T* ptr);

src/OpenFOAM/containers/PtrLists/PtrList/PtrListI.H

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2018-2022 OpenCFD Ltd.
+    Copyright (C) 2018-2023 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -103,9 +103,10 @@ inline void Foam::PtrList<T>::clear()
 
 template<class T>
 template<class... Args>
-inline void Foam::PtrList<T>::emplace_back(Args&&... args)
+inline T& Foam::PtrList<T>::emplace_back(Args&&... args)
 {
     UPtrList<T>::push_back(new T(std::forward<Args>(args)...));
+    return this->back();
 }
 
 

src/OpenFOAM/fields/Fields/DynamicField/DynamicField.H

@@ -279,21 +279,23 @@ public:
         template<int AnySizeMin>
         inline void transfer(DynamicField<T, AnySizeMin>& list);
 
-        //- Append an element at the end of the list
+        //- Construct an element at the end of the list,
+        //- return reference to the new list element
+        template<class... Args>
+        inline T& emplace_back(Args&&... args);
+
+        //- Copy append an element at the end of the list
         inline void push_back(const T& val);
 
         //- Move append an element
         inline void push_back(T&& val);
 
-        //- Append a List at the end of this list
+        //- Copy append another list to the end of this list
         inline void push_back(const UList<T>& list);
 
         //- Reduce size by 1 or more elements. Can be called on an empty list.
         inline void pop_back(label n = 1);
 
-        //- Remove and return the last element. Fatal on an empty list.
-        inline T remove();
-
 
     // Reading/writing
 

src/OpenFOAM/fields/Fields/DynamicField/DynamicFieldI.H

@@ -583,6 +583,23 @@ inline void Foam::DynamicField<T, SizeMin>::transfer
 }
 
 
+template<class T, int SizeMin>
+template<class... Args>
+inline T& Foam::DynamicField<T, SizeMin>::emplace_back(Args&&... args)
+{
+    // This could/should be better with inplace construction
+    // (as per std::vector), but currently lacking the methods for that
+    // so resize and move assign
+
+    const label idx = List<T>::size();
+    resize(idx + 1);
+
+    // move assign element
+    this->operator[](idx) = T(std::forward<Args>(args)...);
+    return this->back();
+}
+
+
 template<class T, int SizeMin>
 inline void Foam::DynamicField<T, SizeMin>::push_back
 (
@@ -646,26 +663,6 @@ inline void Foam::DynamicField<T, SizeMin>::pop_back(label n)
 }
 
 
-template<class T, int SizeMin>
-inline T Foam::DynamicField<T, SizeMin>::remove()
-{
-    // Location of last element and simultaneously the new size
-    const label idx = List<T>::size() - 1;
-
-    if (idx < 0)
-    {
-        FatalErrorInFunction
-            << "List is empty" << abort(FatalError);
-    }
-
-    const T& val = List<T>::operator[](idx);
-
-    List<T>::setAddressableSize(idx);
-
-    return val;
-}
-
-
 // * * * * * * * * * * * * * * * Member Operators  * * * * * * * * * * * * * //
 
 template<class T, int SizeMin>