Improved SemanticValue interface.

example/calc.cc

@@ -33,10 +33,10 @@ int main(int argc, const char** argv)
     const char* s = argv[1];
 
     auto reduce = [](const SemanticValues& sv) -> long {
-        auto result = sv[0].val.get<long>();
+        auto result = sv[0].get<long>();
         for (auto i = 1u; i < sv.size(); i += 2) {
-            auto num = sv[i + 1].val.get<long>();
-            auto ope = sv[i].val.get<char>();
+            auto num = sv[i + 1].get<long>();
+            auto ope = sv[i].get<char>();
             switch (ope) {
                 case '+': result += num; break;
                 case '-': result -= num; break;

example/calc2.cc

@@ -32,10 +32,10 @@ int main(int argc, const char** argv)
     const char* s = argv[1];
 
     auto reduce = [](const SemanticValues& sv) -> long {
-        auto result = sv[0].val.get<long>();
+        auto result = sv[0].get<long>();
         for (auto i = 1u; i < sv.size(); i += 2) {
-            auto num = sv[i + 1].val.get<long>();
-            auto ope = sv[i].val.get<char>();
+            auto num = sv[i + 1].get<long>();
+            auto ope = sv[i].get<char>();
             switch (ope) {
                 case '+': result += num; break;
                 case '-': result -= num; break;

example/calc3.cc

@@ -51,7 +51,7 @@ struct ast_ope : public ast_node
         return SemanticValues::reduce(
             sv.begin() + 1,
             sv.end(),
-            sv[0].val.get<shared_ptr<ast_node>>(),
+            sv[0].get<shared_ptr<ast_node>>(),
             [](shared_ptr<ast_node> r, SemanticValues::const_iterator i) {
                 auto ope = (i++)->val.get<char>();
                 auto nd = (i++)->val.get<shared_ptr<ast_node>>();

peglib.h

@@ -158,6 +158,16 @@ struct SemanticValue {
     SemanticValue(const any& _val, const char* _name, const char* _s, size_t _l)
         : val(_val), name(_name), s(_s), l(_l) {}
 
+    template <typename T>
+    T& get() {
+        return val.get<T>();
+    }
+
+    template <typename T>
+    const T& get() const {
+        return val.get<T>();
+    }
+
     any         val;
     const char* name;
     const char* s;