Add parameter-indexing utility

This creates a map from parameter names to their indices.

Author: smowton

src/util/parameter_indices.cpp

@@ -0,0 +1,10 @@
+
+#include "parameter_indices.h"
+
+std::map<irep_idt,std::size_t> get_parameter_indices(const code_typet& fn_type)
+{
+  std::map<irep_idt,std::size_t>  parameter_indices;
+  for (std::size_t  i = 0UL; i != fn_type.parameters().size(); ++i)
+    parameter_indices.insert({fn_type.parameters().at(i).get_identifier(),i});
+  return parameter_indices;
+}

src/util/parameter_indices.h

@@ -0,0 +1,9 @@
+#ifndef PARAMETER_INDICES_H
+#define PARAMETER_INDICES_H
+
+#include <unordered_map>
+#include "std_types.h"
+
+std::map<irep_idt,std::size_t> get_parameter_indices(const code_typet& fn_type);
+
+#endif