Re #7822. Add a method to clear all but the last value.

This will modify a TimeSeriesProperty to keep only the last entry. Note
that 'last' means the last added, unless the property has been sorted
first.

Code/Mantid/Framework/Kernel/inc/MantidKernel/ITimeSeriesProperty.h

@@ -44,6 +44,8 @@ class ITimeSeriesProperty
   virtual int realSize() const = 0;
   /// Deletes the series of values in the property
   virtual void clear() = 0;
+  /// Deletes all but the 'last entry' in the property
+  virtual void clearOutdated() = 0;
 
   /// Virtual destructor
   virtual ~ITimeSeriesProperty() {}

Code/Mantid/Framework/Kernel/inc/MantidKernel/TimeSeriesProperty.h

@@ -233,6 +233,8 @@ namespace Mantid
 
       /// Deletes the series of values in the property
       void clear();
+      /// Deletes all but the 'last entry' in the property
+      void clearOutdated();
       /// Clears and creates a TimeSeriesProperty from these parameters
       void create(const Kernel::DateAndTime &start_time, const std::vector<double> & time_sec, const std::vector<TYPE> & new_values);
       /// Clears and creates a TimeSeriesProperty from these parameters

Code/Mantid/Framework/Kernel/src/TimeSeriesProperty.cpp

@@ -1068,6 +1068,23 @@ namespace Mantid
       m_filterApplied = false;
     }
 
+    /** Clears out all but the last value in the property.
+     *  The last value is the last entry in the m_values vector - no sorting is
+     *  done or checked for to ensure that the last value is the most recent in time.
+     *  It is up to the client to call sort() first if this is a requirement.
+     */
+    template<typename TYPE>
+    void TimeSeriesProperty<TYPE>::clearOutdated()
+    {
+      if ( realSize() > 1 )
+      {
+        auto lastValue = m_values.back();
+        clear();
+        m_values.push_back(lastValue);
+        m_size = 1;
+      }
+    }
+
     /**
      * Clears and creates a TimeSeriesProperty from these parameters:
      *  @param start_time :: The reference time as a boost::posix_time::ptime value

Code/Mantid/Framework/Kernel/test/TimeSeriesPropertyTest.h

@@ -10,6 +10,7 @@
 #include "MantidKernel/CPUTimer.h"
 #include "algorithm"
 #include <vector>
+#include <boost/scoped_ptr.hpp>
 
 using namespace Mantid::Kernel;
 
@@ -965,19 +966,49 @@ class TimeSeriesPropertyTest : public CxxTest::TestSuite
 
   void test_clear()
   {
-    TimeSeriesProperty<int> * p = new TimeSeriesProperty<int>("aProp");
+    boost::scoped_ptr<TimeSeriesProperty<int>> p(new TimeSeriesProperty<int>("aProp"));
     p->addValue("2007-11-30T16:17:00",1);
 
     TS_ASSERT_EQUALS( p->size(), 1);
     TS_ASSERT_EQUALS( p->realSize(), 1);
 
-    ITimeSeriesProperty * pi = p;
+    ITimeSeriesProperty * pi = p.get();
     TS_ASSERT_THROWS_NOTHING( pi->clear() );
 
     TS_ASSERT_EQUALS( p->size(), 0);
     TS_ASSERT_EQUALS( p->realSize(), 0);
   }
 
+  void test_clearOutdated()
+  {
+    boost::scoped_ptr<TimeSeriesProperty<int>> p(new TimeSeriesProperty<int>("aProp"));
+    p->addValue("2007-11-30T16:17:00",99);
+
+    ITimeSeriesProperty * pi = p.get();
+    TS_ASSERT_THROWS_NOTHING( pi->clearOutdated() );
+    // No change
+    TS_ASSERT_EQUALS( p->size(), 1);
+    TS_ASSERT_EQUALS( p->realSize(), 1);
+    TS_ASSERT_EQUALS( p->lastValue(), 99);
+
+    DateAndTime t("2007-11-30T15:17:00");
+    p->addValue(t,88);
+    TS_ASSERT_EQUALS( p->size(), 2);
+
+    TS_ASSERT_THROWS_NOTHING( pi->clearOutdated() );
+    TS_ASSERT_EQUALS( p->size(), 1);
+    TS_ASSERT_EQUALS( p->realSize(), 1);
+    // Note that it kept the last-added entry even though its time is earlier
+    TS_ASSERT_EQUALS( p->lastTime(), t);
+    TS_ASSERT_EQUALS( p->firstValue(), 88);
+
+    TimeSeriesProperty<double> pp("empty");
+    TS_ASSERT_THROWS_NOTHING( pp.clearOutdated() );
+    // No change
+    TS_ASSERT_EQUALS( pp.size(), 0);
+    TS_ASSERT_EQUALS( pp.realSize(), 0);
+  }
+
   /*
    * Test 2 create() functions by creating 3 properties in different approaches.
    */