Add RBParameters::get_extra_step_value()

Initially I did not think I would need full multi-step support for
getting the "extra" parameters, but it turns out we do, so I'm adding
it now.

Author: jwpeterson

include/reduced_basis/rb_parameters.h

@@ -198,14 +198,14 @@ class RBParameters
    * Get the value of the specified parameter at the specified step,
    * throwing an error if it does not exist.
    */
-  Real get_step_value(const std::string & param_name, std::size_t index) const;
+  Real get_step_value(const std::string & param_name, std::size_t step) const;
 
   /**
    * Get the value of the specified parameter at the specified step,
    * returning the provided default value if either the parameter is
    * not defined or the step is invalid.
    */
-  Real get_step_value(const std::string & param_name, std::size_t index, const Real & default_val) const;
+  Real get_step_value(const std::string & param_name, std::size_t step, const Real & default_val) const;
 
   /**
    * Set the value of the specified parameter. If param_name
@@ -244,6 +244,19 @@ class RBParameters
    */
   Real get_extra_value(const std::string & param_name, const Real & default_val) const;
 
+  /**
+   * Get the value of the specified "extra" parameter at the specified step,
+   * throwing an error if it does not exist.
+   */
+  Real get_extra_step_value(const std::string & param_name, std::size_t step) const;
+
+  /**
+   * Get the value of the specified extra parameter at the specified step,
+   * returning the provided default value if either the parameter is
+   * not defined or the step is invalid.
+   */
+  Real get_extra_step_value(const std::string & param_name, std::size_t step, const Real & default_val) const;
+
   /**
    * Set the value of the specified extra parameter. If param_name
    * doesn't already exist, it is added to the extra parameters.

src/reduced_basis/rb_parameters.C

@@ -154,6 +154,20 @@ Real RBParameters::get_extra_value(const std::string & param_name, const Real &
   return ((it != _extra_parameters.end() && it->second.size() != 0) ? it->second[0] : default_val);
 }
 
+Real RBParameters::get_extra_step_value(const std::string & param_name, std::size_t step) const
+{
+  const auto & vec = libmesh_map_find(_extra_parameters, param_name);
+  libmesh_error_msg_if(step >= vec.size(), "Error getting value for parameter " << param_name);
+  return vec[step];
+}
+
+Real RBParameters::get_extra_step_value(const std::string & param_name, std::size_t step, const Real & default_val) const
+{
+  // same as get_step_value(param_name, index, default_val) but for the map of extra parameters
+  auto it = _extra_parameters.find(param_name);
+  return ((it != _extra_parameters.end() && step < it->second.size()) ? it->second[step] : default_val);
+}
+
 void RBParameters::set_extra_value(const std::string & param_name, Real value)
 {
   // Same as set_value(param_name, value) but for the map of extra parameters