transparent std::array conversion (fixes #97)

docs/basics.rst

@@ -251,6 +251,8 @@ as arguments and return values, refer to the section on binding :ref:`classes`.
 +------------------------+--------------------------+-----------------------+
 | std::complex<T>        | Complex numbers          | pybind11/complex.h    |
 +------------------------+--------------------------+-----------------------+
+| std::array<T, Size>    | STL static array         | pybind11/stl.h        |
++------------------------+--------------------------+-----------------------+
 | std::vector<T>         | STL dynamic array        | pybind11/stl.h        |
 +------------------------+--------------------------+-----------------------+
 | std::map<T1, T2>       | STL ordered map          | pybind11/stl.h        |

example/example2.cpp

@@ -66,6 +66,11 @@ public:
         return list;
     }
 
+    /* C++ STL data types are automatically casted */
+    std::array<std::string, 2> get_array() {
+        return std::array<std::string, 2> {{ "array entry 1" , "array entry 2"}};
+    }
+
     /* Easily iterate over a dictionary using a C++11 range-based for loop */
     void print_dict(py::dict dict) {
         for (auto item : dict)
@@ -114,6 +119,13 @@ public:
         return std::make_tuple(std::get<2>(input), std::get<1>(input), std::get<0>(input));
     }
 
+    /* STL data types (such as arrays) are automatically casted from Python */
+    void print_array(std::array<std::string, 2> &array) {
+        int index = 0;
+        for (auto item : array)
+            std::cout << "array item " << index++ << ": " << item << std::endl;
+    }
+
     void throw_exception() {
         throw std::runtime_error("This exception was intentionally thrown.");
     }
@@ -135,12 +147,14 @@ void init_ex2(py::module &m) {
         .def("get_list_2", &Example2::get_list_2, "Return a C++ list")
         .def("get_set", &Example2::get_set, "Return a Python set")
         .def("get_set2", &Example2::get_set, "Return a C++ set")
+        .def("get_array", &Example2::get_array, "Return a C++ array")
         .def("print_dict", &Example2::print_dict, "Print entries of a Python dictionary")
         .def("print_dict_2", &Example2::print_dict_2, "Print entries of a C++ dictionary")
         .def("print_set", &Example2::print_set, "Print entries of a Python set")
         .def("print_set_2", &Example2::print_set_2, "Print entries of a C++ set")
         .def("print_list", &Example2::print_list, "Print entries of a Python list")
         .def("print_list_2", &Example2::print_list_2, "Print entries of a C++ list")
+        .def("print_array", &Example2::print_array, "Print entries of a C++ array")
         .def("pair_passthrough", &Example2::pair_passthrough, "Return a pair in reversed order")
         .def("tuple_passthrough", &Example2::tuple_passthrough, "Return a triple in reversed order")
         .def("throw_exception", &Example2::throw_exception, "Throw an exception")

example/example2.py

@@ -46,6 +46,10 @@ list_result = instance.get_list_2()
 list_result.append('value2')
 instance.print_list_2(list_result)
 
+array_result = instance.get_array()
+print(array_result)
+instance.print_array(array_result)
+
 try:
     instance.throw_exception()
 except Exception as e:

example/example2.ref

@@ -17,6 +17,9 @@ list item 0: overwritten
 list item 1: value2
 list item 0: value
 list item 1: value2
+[u'array entry 1', u'array entry 2']
+array item 0: array entry 1
+array item 1: array entry 2
 This exception was intentionally thrown.
 (u'test', True)
 (5L, u'test', True)
@@ -30,6 +33,11 @@ class EExxaammppllee22(__builtin__.object)
  |  ____iinniitt____(...)
  |      x.__init__(...) initializes x; see help(type(x)) for signature
  |  
+ |  ggeett__aarrrraayy(...)
+ |      Signature : (example.Example2) -> list<unicode>[2]
+ |      
+ |      Return a C++ array
+ |  
  |  ggeett__ddiicctt(...)
  |      Signature : (example.Example2) -> dict
  |      
@@ -65,6 +73,11 @@ class EExxaammppllee22(__builtin__.object)
  |      
  |      Return a pair in reversed order
  |  
+ |  pprriinntt__aarrrraayy(...)
+ |      Signature : (example.Example2, list<unicode>[2]) -> NoneType
+ |      
+ |      Print entries of a C++ array
+ |  
  |  pprriinntt__ddiicctt(...)
  |      Signature : (example.Example2, dict) -> NoneType
  |      

include/pybind11/descr.h

@@ -78,6 +78,15 @@ template <size_t Size> constexpr descr<Size - 1, 0> _(char const(&text)[Size]) {
     return descr<Size - 1, 0>(text, { nullptr });
 }
 
+template <size_t Rem, size_t... Digits> struct int_to_str : int_to_str<Rem/10, Rem%10, Digits...> { };
+template <size_t...Digits> struct int_to_str<0, Digits...> {
+    static constexpr auto digits = descr<sizeof...(Digits), 0>({ ('0' + Digits)..., '\0' }, { nullptr });
+};
+
+template <size_t Size> auto constexpr _() {
+    return int_to_str<Size / 10, Size % 10>::digits;
+}
+
 template <typename Type> constexpr descr<1, 1> _() {
     return descr<1, 1>({ '%', '\0' }, { &typeid(Type), nullptr });
 }
@@ -149,6 +158,11 @@ template <typename Type> PYBIND11_NOINLINE descr _() {
     return descr("%", types);
 }
 
+template <size_t Size> PYBIND11_NOINLINE descr _() {
+    const std::type_info *types[1] = { nullptr };
+    return descr(std::to_string(Size).c_str(), types);
+}
+
 PYBIND11_NOINLINE inline descr concat() { return _(""); }
 PYBIND11_NOINLINE inline descr concat(descr &&d) { return d; }
 template <typename... Args> PYBIND11_NOINLINE descr concat(descr &&d, Args&&... args) { return std::move(d) + _(", ") + concat(std::forward<Args>(args)...); }

include/pybind11/stl.h

@@ -22,9 +22,9 @@
 NAMESPACE_BEGIN(pybind11)
 NAMESPACE_BEGIN(detail)
 
-template <typename Value, typename Alloc> struct type_caster<std::vector<Value, Alloc>> {
+template <typename Type, typename Alloc> struct type_caster<std::vector<Type, Alloc>> {
-    typedef std::vector<Value, Alloc> type;
+    typedef std::vector<Type, Alloc> vector_type;
-    typedef type_caster<Value> value_conv;
+    typedef type_caster<Type> value_conv;
 public:
     bool load(handle src, bool convert) {
         list l(src, true);
@@ -36,12 +36,12 @@ public:
         for (auto it : l) {
             if (!conv.load(it, convert))
                 return false;
-            value.push_back((Value) conv);
+            value.push_back((Type) conv);
         }
         return true;
     }
 
-    static handle cast(const type &src, return_value_policy policy, handle parent) {
+    static handle cast(const vector_type &src, return_value_policy policy, handle parent) {
         list l(src.size());
         size_t index = 0;
         for (auto const &value: src) {
@@ -52,7 +52,41 @@ public:
         }
         return l.release();
     }
-    PYBIND11_TYPE_CASTER(type, _("list<") + value_conv::name() + _(">"));
+    PYBIND11_TYPE_CASTER(vector_type, _("list<") + value_conv::name() + _(">"));
+};
+
+template <typename Type, size_t Size> struct type_caster<std::array<Type, Size>> {
+    typedef std::array<Type, Size> array_type;
+    typedef type_caster<Type> value_conv;
+public:
+    bool load(handle src, bool convert) {
+        list l(src, true);
+        if (!l.check())
+            return false;
+        if (l.size() != Size)
+            return false;
+        value_conv conv;
+        size_t ctr = 0;
+        for (auto it : l) {
+            if (!conv.load(it, convert))
+                return false;
+            value[ctr++] = (Type) conv;
+        }
+        return true;
+    }
+
+    static handle cast(const array_type &src, return_value_policy policy, handle parent) {
+        list l(Size);
+        size_t index = 0;
+        for (auto const &value: src) {
+            object value_ = object(value_conv::cast(value, policy, parent), false);
+            if (!value_)
+                return handle();
+            PyList_SET_ITEM(l.ptr(), index++, value_.release().ptr()); // steals a reference
+        }
+        return l.release();
+    }
+    PYBIND11_TYPE_CASTER(array_type, _("list<") + value_conv::name() + _(">") + _("[") + _<Size>() + _("]"));
 };
 
 template <typename Key, typename Compare, typename Alloc> struct type_caster<std::set<Key, Compare, Alloc>> {