From 4ac67d6adeff03362b951e5a75a46233d4c3ea18 Mon Sep 17 00:00:00 2001
From: Henry Weller <http://cfd.direct>
Date: Wed, 30 Mar 2016 18:17:51 +0100
Subject: [PATCH] Field: Add block member function to return sub-sets of the
 field as VectorSpaces

---
 src/OpenFOAM/fields/Fields/Field/Field.C | 13 +++++++++++++
 src/OpenFOAM/fields/Fields/Field/Field.H |  3 +++
 2 files changed, 16 insertions(+)

diff --git a/src/OpenFOAM/fields/Fields/Field/Field.C b/src/OpenFOAM/fields/Fields/Field/Field.C
index 4b628788e..f59091282 100644
--- a/src/OpenFOAM/fields/Fields/Field/Field.C
+++ b/src/OpenFOAM/fields/Fields/Field/Field.C
@@ -611,6 +611,19 @@ void Foam::Field<Type>::replace
 }
 
 
+template<class Type>
+template<class VSForm>
+VSForm Foam::Field<Type>::block(const label start) const
+{
+    VSForm vs;
+    for (direction i=0; i<VSForm::nComponents; i++)
+    {
+        vs[i] = this->operator[](start + i);
+    }
+    return vs;
+}
+
+
 template<class Type>
 Foam::tmp<Foam::Field<Type>> Foam::Field<Type>::T() const
 {
diff --git a/src/OpenFOAM/fields/Fields/Field/Field.H b/src/OpenFOAM/fields/Fields/Field/Field.H
index 3c5510be5..2e531dfc8 100644
--- a/src/OpenFOAM/fields/Fields/Field/Field.H
+++ b/src/OpenFOAM/fields/Fields/Field/Field.H
@@ -333,6 +333,9 @@ public:
         //- Replace a component field of the field
         void replace(const direction, const cmptType&);
 
+        template<class VSForm>
+        VSForm block(const label start) const;
+
         //- Return the field transpose (only defined for second rank tensors)
         tmp<Field<Type>> T() const;