Add a function to remove an item from a map, checking for existence

[libs/core.git] / source / core / maputils.h

diff --git a/source/core/maputils.h b/source/core/maputils.h
index 9548714658d806fad41614357bc0e60fa8444cdf..ecee0fbea45955dbf9bef8f8bf296bb387b3e414 100644 (file)
--- a/source/core/maputils.h
+++ b/source/core/maputils.h
@@ -3,14 +3,54 @@
 
 #include <stdexcept>
 #include <typeinfo>
+#include <msp/strings/lexicalcast.h>
 
 namespace Msp {
 
+namespace MapUtilsInternal {
+
+/* This dummy struct is used to introduce a conversion, making the overloaded
+operator below worse than the templated one provided in lexicalcast.h. */
+struct Any
+{
+       template<typename T>
+       Any(const T &) { }
+};
+
+/* This must be hidden in the internal namespace to avoid interfering with
+other things. */
+inline void operator<<(LexicalConverter &, Any)
+{ }
+
+template<typename T>
+static std::string stringify_key(const T &k)
+{
+       try
+       {
+               LexicalConverter conv((Fmt()));
+               conv<<k;
+               return conv.get();
+       }
+       catch(const lexical_error &)
+       {
+               return "<cannot display value>";
+       }
+}
+
+} // namespace Internal
+
 class key_error: public std::runtime_error
 {
 public:
-       key_error(const std::type_info &);
-       ~key_error() throw() { }
+       template<typename T>
+       key_error(const T &k):
+               runtime_error(make_what(typeid(T), MapUtilsInternal::stringify_key(k)))
+       { }
+
+       virtual ~key_error() throw() { }
+
+private:
+       static std::string make_what(const std::type_info &, const std::string &);
 };
 
 
@@ -19,7 +59,7 @@ typename T::mapped_type &get_item(T &map, const typename T::key_type &key)
 {
        typename T::iterator i = map.find(key);
        if(i==map.end())
-               throw key_error(typeid(T));
+               throw key_error(key);
 
        return i->second;
 }
@@ -29,7 +69,7 @@ const typename T::mapped_type &get_item(const T &map, const typename T::key_type
 {
        typename T::const_iterator i = map.find(key);
        if(i==map.end())
-               throw key_error(typeid(T));
+               throw key_error(key);
 
        return i->second;
 }
@@ -38,11 +78,20 @@ template<typename T>
 const typename T::iterator insert_unique(T &map, const typename T::key_type &key, const typename T::mapped_type &item)
 {
        if(map.count(key))
-               throw key_error(typeid(T));
+               throw key_error(key);
 
        return map.insert(typename T::value_type(key, item)).first;
 }
 
+template<typename T>
+void remove_existing(T &map, const typename T::key_type &key)
+{
+       if(!map.count(key))
+               throw key_error(key);
+
+       map.erase(key);
+}
+
 } // namespace Msp
 
 #endif