Refs #8913 Add a couple of additional methods for convenience.

These are consistent with the functionality that is available in WorkspaceHistory.

Code/Mantid/Framework/API/inc/MantidAPI/AlgorithmHistory.h

@@ -87,6 +87,10 @@ class MANTID_API_DLL AlgorithmHistory
   const std::vector<Kernel::PropertyHistory>& getProperties() const {return m_properties;}
   /// get the child histories of this history object
   AlgorithmHistories getChildHistories() const { return m_childHistories; }
+  /// Retrieve a child algorithm history by index
+  const AlgorithmHistory & getChildAlgorithmHistory(const size_t index) const;
+  /// Retrieve the number of child algorithms
+  size_t childHistorySize() const;
   /// print contents of object
   void printSelf(std::ostream&,const int indent = 0) const;
   /// Less than operator

Code/Mantid/Framework/API/src/AlgorithmHistory.cpp

@@ -91,6 +91,31 @@ void AlgorithmHistory::addChildHistory(const AlgorithmHistory& childHist)
   m_childHistories.insert(childHist);
 }
 
+/*
+ Return the child history length
+ */
+size_t AlgorithmHistory::childHistorySize() const
+{
+  return m_childHistories.size();
+}
+
+/**
+ * Retrieve a child algorithm history by index
+ * @param index ::  An index within the child algorithm history set
+ * @returns A reference to a const AlgorithmHistory object
+ * @throws std::out_of_range error if the index is invalid
+ */
+const AlgorithmHistory & AlgorithmHistory::getChildAlgorithmHistory(const size_t index) const
+{
+  if( index >= this->getChildHistories().size() )
+  {
+    throw std::out_of_range("AlgorithmHistory::getAlgorithmHistory() - Index out of range");
+  }
+  AlgorithmHistories::const_iterator start = m_childHistories.begin();
+  std::advance(start, index);
+  return *start;
+}
+
 /** Set the duration time of the algorithm in the history
  *  @param duration :: The time the algorithm took to execute
  */