multicover: make getChrIndex const

multicover.hpp

@@ -46,7 +46,7 @@ public:
   /**
    * @return the chromosome index given its name
    */
-  size_t getChrIndex(const std::string chr);
+  size_t getChrIndex(const std::string chr) const;
   
   /**
    * @return the name of the i-th chromosome
@@ -116,7 +116,7 @@ std::string MultiCover<bv>::getChrName(size_t i) const {
 }
 
 template <class bv>
-size_t MultiCover<bv>::getChrIndex(const std::string chr) {
+size_t MultiCover<bv>::getChrIndex(const std::string chr) const {
   for (size_t i = 0; i < nb_targets; i++)
     if (target_names[i] == chr)
       return i;