ENH: additional IndirectList static methods

- uniq() : creates an IndirectList with duplicated entries
  filtered out

- subset() : creates an IndirectList with positions that satisfy
  a condition predicate.

- subset_if() : creates an IndirectList with values that satisfy a
  given predicate.

  An indirect subset will be cheaper than creating a subset copy
  of the original data, and also allows modification.

STYLE: combine UIndirectList.H into UIndirectList.H (reduce file clutter)

applications/test/ListOps/Test-ListOps.C

@@ -151,6 +151,10 @@ int main(int argc, char *argv[])
         << subsetList(test6, evenNonZero) << nl
         << endl;
 
+    Info<< "Subset of non-zero, even values: "
+        << IndirectList<label>::subset_if(test6, evenNonZero) << nl
+        << endl;
+
     test6.append(identity(13, 12));
 
     Info<< "Randomized: " << flatOutput(test6) << endl;

applications/test/UIndirectList/Test-UIndirectList.C

@@ -27,7 +27,7 @@ Description
 
 \*---------------------------------------------------------------------------*/
 
-#include "UIndirectList.H"
+#include "IndirectList.H"
 #include "DynamicList.H"
 #include "IOstreams.H"
 #include "ListOps.H"

applications/test/minMax1/Test-minMax1.C

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2019 OpenCFD Ltd.
+    Copyright (C) 2019-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -190,6 +190,8 @@ int main(int argc, char *argv[])
             << nl;
 
         Info<< "Subset = " << subsetList(values1, limiter) << nl;
+        Info<< "Subset = "
+            << IndirectList<scalar>::subset_if(values1, limiter) << nl;
 
         Info<< nl << "test clip() with limiter: " << limiter << nl;
         for (const scalar& val : values1)

applications/test/sort/Test-sortList.C

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011 OpenFOAM Foundation
-    Copyright (C) 2017-2019 OpenCFD Ltd.
+    Copyright (C) 2017-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -28,7 +28,9 @@ Description
 
 \*---------------------------------------------------------------------------*/
 
+#include "SortList.H"
 #include "SortableList.H"
+#include "IndirectList.H"
 #include "ListOps.H"
 #include "HashSet.H"
 #include "stringOps.H"
@@ -49,6 +51,18 @@ void printInfo(const SortableList<T>& list)
 
 int main(int argc, char *argv[])
 {
+    {
+        const labelList orig({7, 9, 7, 12, 9, 1, 12, 2, 4, 7, 4, 0});
+
+        Info<< "original list: " << flatOutput(orig) << endl;
+
+        auto unique = IndirectList<label>::uniq(orig);
+
+        Info<< "unique  list: " << flatOutput(unique) << endl;
+        Info<< "unique  idx : " << flatOutput(unique.addressing()) << endl;
+    }
+
+
     const labelList orig({7, 9, 1, 2, 4, 7, 4, 0});
 
     labelList order;