minor doc & style fixes

docs/advanced.rst

@@ -551,27 +551,150 @@ and the Python ``list``, ``set`` and ``dict`` data structures are automatically
 enabled. The types ``std::pair<>`` and ``std::tuple<>`` are already supported
 out of the box with just the core :file:`pybind11/pybind11.h` header.
 
-Alternatively it might be desirable to bind STL containers as native C++ classes,
+The major downside of these implicit conversions is that containers must be
-eliminating the need of converting back and forth between C++ representation
+converted (i.e. copied) on every Python->C++ and C++->Python transition, which
-and Python one. The downside of this approach in this case users will have to
+can have implications on the program semantics and performance. Please read the
-deal with C++ containers directly instead of using already familiar Python lists
+next sections for more details and alternative approaches that avoid this.
-or dicts.
-
-Pybind11 provide set of binder functions to bind various STL containers like vectors,
-maps etc. All binder functions are designed to return instances of pybind11::class_
-objects so developers can bind extra functions if needed. For complete set of
-available functions please see :file:`pybind11/stl_bind.h`. For an example on using
-this feature, please see :file:`tests/test_stl_binders.cpp`.
 
 .. note::
 
-    Arbitrary nesting of any of these types is supported.
+    Arbitrary nesting of any of these types is possible.
 
 .. seealso::
 
     The file :file:`tests/test_python_types.cpp` contains a complete
     example that demonstrates how to pass STL data types in more detail.
 
+.. _opaque:
+
+Treating STL data structures as opaque objects
+==============================================
+
+pybind11 heavily relies on a template matching mechanism to convert parameters
+and return values that are constructed from STL data types such as vectors,
+linked lists, hash tables, etc. This even works in a recursive manner, for
+instance to deal with lists of hash maps of pairs of elementary and custom
+types, etc.
+
+However, a fundamental limitation of this approach is that internal conversions
+between Python and C++ types involve a copy operation that prevents
+pass-by-reference semantics. What does this mean?
+
+Suppose we bind the following function
+
+.. code-block:: cpp
+
+    void append_1(std::vector<int> &v) {
+       v.push_back(1);
+    }
+
+and call it from Python, the following happens:
+
+.. code-block:: pycon
+
+   >>> v = [5, 6]
+   >>> append_1(v)
+   >>> print(v)
+   [5, 6]
+
+As you can see, when passing STL data structures by reference, modifications
+are not propagated back the Python side. A similar situation arises when
+exposing STL data structures using the ``def_readwrite`` or ``def_readonly``
+functions:
+
+.. code-block:: cpp
+
+    /* ... definition ... */
+
+    class MyClass {
+        std::vector<int> contents;
+    };
+
+    /* ... binding code ... */
+
+    py::class_<MyClass>(m, "MyClass")
+        .def(py::init<>)
+        .def_readwrite("contents", &MyClass::contents);
+
+In this case, properties can be read and written in their entirety. However, an
+``append`` operaton involving such a list type has no effect:
+
+.. code-block:: pycon
+
+   >>> m = MyClass()
+   >>> m.contents = [5, 6]
+   >>> print(m.contents)
+   [5, 6]
+   >>> m.contents.append(7)
+   >>> print(m.contents)
+   [5, 6]
+
+Finally, the involved copy operations can be costly when dealing with very
+large lists. To deal with all of the above situations, pybind11 provides a
+macro named ``PYBIND11_MAKE_OPAQUE(T)`` that disables the template-based
+conversion machinery of types, thus rendering them *opaque*. The contents of
+opaque objects are never inspected or extracted, hence they *can* be passed by
+reference. For instance, to turn ``std::vector<int>`` into an opaque type, add
+the declaration
+
+.. code-block:: cpp
+
+    PYBIND11_MAKE_OPAQUE(std::vector<int>);
+
+before any binding code (e.g. invocations to ``class_::def()``, etc.). This
+macro must be specified at the top level (and outside of any namespaces), since
+it instantiates a partial template overload. If your binding code consists of
+multiple compilation units, it must be present in every file preceding any
+usage of ``std::vector<int>``. Opaque types must also have a corresponding
+``class_`` declaration to associate them with a name in Python, and to define a
+set of available operations, e.g.:
+
+.. code-block:: cpp
+
+    py::class_<std::vector<int>>(m, "IntVector")
+        .def(py::init<>())
+        .def("clear", &std::vector<int>::clear)
+        .def("pop_back", &std::vector<int>::pop_back)
+        .def("__len__", [](const std::vector<int> &v) { return v.size(); })
+        .def("__iter__", [](std::vector<int> &v) {
+           return py::make_iterator(v.begin(), v.end());
+        }, py::keep_alive<0, 1>()) /* Keep vector alive while iterator is used */
+        // ....
+
+The ability to expose STL containers as native Python objects is a fairly
+common request, hence pybind11 also provides an optional header file named
+:file:`pybind11/stl_bind.h` that does exactly this. The mapped containers try
+to match the behavior of their native Python counterparts as much as possible.
+
+The following example showcases usage of :file:`pybind11/stl_bind.h`:
+
+.. code-block:: cpp
+
+    // Don't forget this
+    #include <pybind11/stl_bind.h>
+
+    PYBIND11_MAKE_OPAQUE(std::vector<int>);
+    PYBIND11_MAKE_OPAQUE(std::map<std::string, double>);
+
+    // ...
+
+    // later in binding code:
+    py::bind_vector<std::vector<int>>(m, "VectorInt");
+    py::bind_map<std::map<std::string, double>>(m, "MapStringDouble");
+
+Please take a look at the :ref:`macro_notes` before using the
+``PYBIND11_MAKE_OPAQUE`` macro.
+
+.. seealso::
+
+    The file :file:`tests/test_opaque_types.cpp` contains a complete
+    example that demonstrates how to create and expose opaque types using
+    pybind11 in more detail.
+
+    The file :file:`tests/test_stl_binders.cpp` shows how to use the
+    convenience STL container wrappers.
+
+
 Binding sequence data types, iterators, the slicing protocol, etc.
 ==================================================================
 
@@ -1103,108 +1226,6 @@ section.
     The ``py::exception`` wrapper for creating custom exceptions cannot (yet)
     be used as a ``py::base``.
 
-.. _opaque:
-
-Treating STL data structures as opaque objects
-==============================================
-
-pybind11 heavily relies on a template matching mechanism to convert parameters
-and return values that are constructed from STL data types such as vectors,
-linked lists, hash tables, etc. This even works in a recursive manner, for
-instance to deal with lists of hash maps of pairs of elementary and custom
-types, etc.
-
-However, a fundamental limitation of this approach is that internal conversions
-between Python and C++ types involve a copy operation that prevents
-pass-by-reference semantics. What does this mean?
-
-Suppose we bind the following function
-
-.. code-block:: cpp
-
-    void append_1(std::vector<int> &v) {
-       v.push_back(1);
-    }
-
-and call it from Python, the following happens:
-
-.. code-block:: pycon
-
-   >>> v = [5, 6]
-   >>> append_1(v)
-   >>> print(v)
-   [5, 6]
-
-As you can see, when passing STL data structures by reference, modifications
-are not propagated back the Python side. A similar situation arises when
-exposing STL data structures using the ``def_readwrite`` or ``def_readonly``
-functions:
-
-.. code-block:: cpp
-
-    /* ... definition ... */
-
-    class MyClass {
-        std::vector<int> contents;
-    };
-
-    /* ... binding code ... */
-
-    py::class_<MyClass>(m, "MyClass")
-        .def(py::init<>)
-        .def_readwrite("contents", &MyClass::contents);
-
-In this case, properties can be read and written in their entirety. However, an
-``append`` operaton involving such a list type has no effect:
-
-.. code-block:: pycon
-
-   >>> m = MyClass()
-   >>> m.contents = [5, 6]
-   >>> print(m.contents)
-   [5, 6]
-   >>> m.contents.append(7)
-   >>> print(m.contents)
-   [5, 6]
-
-To deal with both of the above situations, pybind11 provides a macro named
-``PYBIND11_MAKE_OPAQUE(T)`` that disables the template-based conversion
-machinery of types, thus rendering them *opaque*. The contents of opaque
-objects are never inspected or extracted, hence they can be passed by
-reference. For instance, to turn ``std::vector<int>`` into an opaque type, add
-the declaration
-
-.. code-block:: cpp
-
-    PYBIND11_MAKE_OPAQUE(std::vector<int>);
-
-before any binding code (e.g. invocations to ``class_::def()``, etc.). This
-macro must be specified at the top level, since instantiates a partial template
-overload. If your binding code consists of multiple compilation units, it must
-be present in every file preceding any usage of ``std::vector<int>``. Opaque
-types must also have a corresponding ``class_`` declaration to associate them
-with a name in Python, and to define a set of available operations:
-
-.. code-block:: cpp
-
-    py::class_<std::vector<int>>(m, "IntVector")
-        .def(py::init<>())
-        .def("clear", &std::vector<int>::clear)
-        .def("pop_back", &std::vector<int>::pop_back)
-        .def("__len__", [](const std::vector<int> &v) { return v.size(); })
-        .def("__iter__", [](std::vector<int> &v) {
-           return py::make_iterator(v.begin(), v.end());
-        }, py::keep_alive<0, 1>()) /* Keep vector alive while iterator is used */
-        // ....
-
-Please take a look at the :ref:`macro_notes` before using this feature.
-
-.. seealso::
-
-    The file :file:`tests/test_opaque_types.cpp` contains a complete
-    example that demonstrates how to create and expose opaque types using
-    pybind11 in more detail.
-
 .. _eigen:
 
 Transparent conversion of dense and sparse Eigen data types

docs/faq.rst

@@ -140,7 +140,7 @@ the included test suite contains the following symbol:
 
     .. code-block:: none
 
-        _​_​Z​N​8​p​y​b​i​n​d​1​1​1​2​c​p​p​_​f​u​n​c​t​i​o​n​C​1​I​v​8​E​x​a​m​p​l​e​2​J​R​N​S​t​3​_​_​1​6​v​e​c​t​o​r​I​N​S​3​_​1​2​b​a​s​i​c​_​s​t​r​i​n​g​I​w​N​S​3​_​1​1​c​h​a​r​_​t​r​a​i​t​s​I​w​E​E​N​S​3​_​9​a​l​l​o​c​a​t​o​r​I​w​E​E​E​E​N​S​8​_​I​S​A​_​E​E​E​E​E​J​N​S​_​4​n​a​m​e​E​N​S​_​7​s​i​b​l​i​n​g​E​N​S​_​9​i​s​_​m​e​t​h​o​d​E​A​2​8​_​c​E​E​E​M​T​0​_​F​T​_​D​p​T​1​_​E​D​p​R​K​T​2​_​
+        _​_​Z​N​8​p​y​b​i​n​d​1​1​1​2​c​p​p​_​f​u​n​c​t​i​o​n​C​1​I​v​8​E​x​a​m​p​l​e​2​J​R​N​S​t​3​_​_​1​6​v​e​c​t​o​r​I​N​S​3​_​1​2​b​a​s​i​c​_​s​t​r​i​n​g​I​w​N​S​3​_​1​1​c​h​a​r​_​t​r​a​i​t​s​I​w​E​E​N​S​3​_​9​a​l​l​o​c​a​t​o​r​I​w​E​E​E​E​N​S​8​_​I​S​A​_​E​E​E​E​E​J​N​S​_​4​n​a​m​e​E​N​S​_​7​s​i​b​l​i​n​g​E​N​S​_​9​i​s​_​m​e​t​h​o​d​E​A​2​8​_​c​E​E​E​M​T​0​_​F​T​_​D​p​T​1​_​E​D​p​R​K​T​2​_
 
 .. only:: not html
 

include/pybind11/stl_bind.h

@@ -12,7 +12,6 @@
 #include "common.h"
 #include "operators.h"
 
-#include <map>
 #include <type_traits>
 #include <utility>
 #include <algorithm>
@@ -356,7 +355,7 @@ pybind11::class_<Vector, holder_type> bind_vector(pybind11::module &m, std::stri
 
 
 //
-// std::map
+// std::map, std::unordered_map
 //
 
 NAMESPACE_BEGIN(detail)
@@ -373,8 +372,8 @@ template <typename Map, typename Class_, typename... Args> void map_if_copy_assi
                auto it = m.find(k);
                if (it != m.end()) it->second = v;
                else m.emplace(k, v);
-           });
+           }
-
+    );
 }
 
 template<typename Map, typename Class_, typename std::enable_if<!std::is_copy_assignable<typename Map::mapped_type>::value, int>::type = 0>
@@ -384,12 +383,15 @@ void map_if_copy_assignable(Class_ &cl) {
 
     cl.def("__setitem__",
            [](Map &m, const KeyType &k, const MappedType &v) {
-               auto r = m.insert( std::make_pair(k, v) ); // We can't use m[k] = v; because value type might not be default constructable
+               // We can't use m[k] = v; because value type might not be default constructable
-               if (!r.second) { // value type might be const so the only way to insert it is to errase it first...
+               auto r = m.insert(std::make_pair(k, v));
+               if (!r.second) {
+                   // value type might be const so the only way to insert it is to erase it first...
                    m.erase(r.first);
-                   m.insert( std::make_pair(k, v) );
+                   m.insert(std::make_pair(k, v));
                }
-           });
+           }
+    );
 }
 
 
@@ -401,8 +403,9 @@ template <typename Map, typename Class_> auto map_if_insertion_operator(Class_ &
             std::ostringstream s;
             s << name << '{';
             bool f = false;
-            for (auto const & kv : m) {
+            for (auto const &kv : m) {
-                if (f) s << ", ";
+                if (f)
+                    s << ", ";
                 s << kv.first << ": " << kv.second;
                 f = true;
             }
@@ -428,16 +431,12 @@ pybind11::class_<Map, holder_type> bind_map(module &m, const std::string &name,
     detail::map_if_insertion_operator<Map, Class_>(cl, name);
 
     cl.def("__bool__",
-        [](const Map &m) -> bool {
+        [](const Map &m) -> bool { return !m.empty(); },
-            return !m.empty();
-        },
         "Check whether the map is nonempty"
     );
 
     cl.def("__iter__",
-        [](Map &m) {
+           [](Map &m) { return pybind11::make_key_iterator(m.begin(), m.end()); },
-            return pybind11::make_key_iterator(m.begin(), m.end());
-        },
            pybind11::keep_alive<0, 1>() /* Essential: keep list alive while iterator exists */
     );
 
@@ -449,18 +448,22 @@ pybind11::class_<Map, holder_type> bind_map(module &m, const std::string &name,
     cl.def("__getitem__",
            [](Map &m, const KeyType &k) -> MappedType {
                auto it = m.find(k);
-               if (it != m.end()) return it->second;
+               if (it == m.end())
-               else throw pybind11::key_error();  // it is not always possible to convert key to string // pybind11::key_error(k)
+                  throw pybind11::key_error();
-   });
+               return it->second;
+           }
+    );
 
     detail::map_if_copy_assignable<Map, Class_>(cl);
 
     cl.def("__delitem__",
            [](Map &m, const KeyType &k) {
                auto it = m.find(k);
-               if (it != m.end()) return m.erase(it);
+               if (it == m.end())
-               else throw pybind11::key_error(); // it is not always possible to convert key to string // pybind11::key_error(k)
+                   throw pybind11::key_error();
-    });
+               return m.erase(it);
+           }
+    );
 
     cl.def("__len__", &Map::size);
 

tests/test_stl_binders.cpp

@@ -10,6 +10,8 @@
 #include "pybind11_tests.h"
 
 #include <pybind11/stl_bind.h>
+#include <map>
+#include <unordered_map>
 
 class El {
 public:
@@ -28,18 +30,18 @@ test_initializer stl_binder_vector([](py::module &m) {
     py::class_<El>(m, "El")
         .def(py::init<int>());
 
-    py::bind_vector< std::vector<unsigned int> >(m, "VectorInt");
+    py::bind_vector<std::vector<unsigned int>>(m, "VectorInt");
-    py::bind_vector< std::vector<bool> >(m, "VectorBool");
+    py::bind_vector<std::vector<bool>>(m, "VectorBool");
 
-    py::bind_vector< std::vector<El> >(m, "VectorEl");
+    py::bind_vector<std::vector<El>>(m, "VectorEl");
 
-    py::bind_vector< std::vector< std::vector<El> > >(m, "VectorVectorEl");
+    py::bind_vector<std::vector<std::vector<El>>>(m, "VectorVectorEl");
 });
 
 test_initializer stl_binder_map([](py::module &m) {
-    py::bind_map< std::map<std::string, double> >(m, "MapStringDouble");
+    py::bind_map<std::map<std::string, double>>(m, "MapStringDouble");
-    py::bind_map< std::unordered_map<std::string, double> >(m, "UnorderedMapStringDouble");
+    py::bind_map<std::unordered_map<std::string, double>>(m, "UnorderedMapStringDouble");
 
-    py::bind_map< std::map<std::string, double const> >(m, "MapStringDoubleConst");
+    py::bind_map<std::map<std::string, double const>>(m, "MapStringDoubleConst");
-    py::bind_map< std::unordered_map<std::string, double const> >(m, "UnorderedMapStringDoubleConst");
+    py::bind_map<std::unordered_map<std::string, double const>>(m, "UnorderedMapStringDoubleConst");
 });

tools/check-style.sh

@@ -1,7 +1,12 @@
 #!/bin/bash
 # 
 # Script to check include/test code for common pybind11 code style errors.
-# Currently just checks for tabs used instead of spaces.
+# 
+# This script currently checks for
+#
+# 1. use of tabs instead of spaces
+# 2. trailing spaces
+# 3. missing space between keyword and parenthesis, e.g.: for(, if(, while(
 # 
 # Invoke as: tools/check-style.sh
 #
@@ -21,6 +26,19 @@ while read -u 3 f; do
     echo "    $f"
 done
 
+found=
+# The mt=41 sets a red background for matched trailing spaces
+exec 3< <(GREP_COLORS='mt=41' grep '\s\+$' include/ tests/*.{cpp,py,h} docs/*.rst -rn --color=always)
+while read -u 3 f; do
+    if [ -z "$found" ]; then
+        echo -e '\e[31m\e[01mError: found trailing spaces in the following files:\e[0m'
+        found=1
+        errors=1
+    fi
+
+    echo "    $f"
+done
+
 found=
 exec 3< <(grep '\<\(if\|for\|while\)(\|){' include/ tests/*.{cpp,py,h} -rn --color=always)
 while read -u 3 line; do