Use sys.prefix as default value for include/library_dir preferences

This means the user can overwrite them by setting the preference.
Previously, the dirs were always appended (for Cython) or prepended
(for C++ standalone).

brian2/codegen/cpp_prefs.py

@@ -111,6 +111,11 @@
     else:
         default_buildopts = ['-w']
 
+if sys.platform == 'win32':
+    prefix_dir = os.path.join(sys.prefix, 'Library')
+else:
+    prefix_dir = sys.prefix
+
 # Preferences
 prefs.register_preferences(
     'codegen.cpp',
@@ -154,26 +159,33 @@
         '''
     ),
     include_dirs=BrianPreference(
-        default=[],
+        default=[os.path.join(prefix_dir, 'include')],
         docs='''
-        Include directories to use. Note that ``$prefix/include`` will be
-        appended to the end automatically, where ``$prefix`` is Python's
-        site-specific directory prefix as returned by `sys.prefix`.
+        Include directories to use.
+        The default value is ``$prefix/include`` (or ``$prefix/Library/include``
+        on Windows), where ``$prefix`` is Python's site-specific directory
+        prefix as returned by `sys.prefix`. This will make compilation use
+        library files installed into a conda environment.
         '''
         ),
     library_dirs=BrianPreference(
-        default=[],
+        default=[os.path.join(prefix_dir, 'lib')],
         docs='''
         List of directories to search for C/C++ libraries at link time.
-        Note that ``$prefix/lib`` will be appended to the end automatically,
-        where ``$prefix`` is Python's site-specific directory prefix as returned
-        by `sys.prefix`.
+        The default value is ``$prefix/lib`` (or ``$prefix/Library/lib``
+        on Windows), where ``$prefix`` is Python's site-specific directory
+        prefix as returned by `sys.prefix`. This will make compilation use
+        library files installed into a conda environment.
         '''
     ),
     runtime_library_dirs=BrianPreference(
-        default=[],
+        default=[os.path.join(prefix_dir, 'lib')],
         docs='''
         List of directories to search for C/C++ libraries at run time.
+        The default value is ``$prefix/lib`` (or ``$prefix/Library/lib``
+        on Windows), where ``$prefix`` is Python's site-specific directory
+        prefix as returned by `sys.prefix`. This will make compilation use
+        library files installed into a conda environment.
         '''
     ),
     libraries=BrianPreference(

brian2/codegen/runtime/cython_rt/cython_rt.py

@@ -93,17 +93,9 @@ def __init__(self, owner, code, variables, variable_indices,
         self.include_dirs = (list(prefs['codegen.cpp.include_dirs']) +
                              compiler_kwds.get('include_dirs', []))
         self.include_dirs = list(prefs['codegen.cpp.include_dirs'])
-        if sys.platform == 'win32':
-            self.include_dirs += [os.path.join(sys.prefix, 'Library', 'include')]
-        else:
-            self.include_dirs += [os.path.join(sys.prefix, 'include')]
 
         self.library_dirs = (list(prefs['codegen.cpp.library_dirs']) +
                              compiler_kwds.get('library_dirs', []))
-        if sys.platform == 'win32':
-            self.library_dirs += [os.path.join(sys.prefix, 'Library', 'lib')]
-        else:
-            self.library_dirs += [os.path.join(sys.prefix, 'lib')]
 
         self.runtime_library_dirs = (list(prefs['codegen.cpp.runtime_library_dirs']),
                                      compiler_kwds.get('runtime_library_dirs', []))

brian2/devices/cpp_standalone/device.py

@@ -205,18 +205,8 @@ def __init__(self):
         self.define_macros = []
         self.headers = []
         self.include_dirs = ['brianlib/randomkit']
-        if sys.platform == 'win32':
-            self.include_dirs += [os.path.join(sys.prefix, 'Library', 'include')]
-        else:
-            self.include_dirs += [os.path.join(sys.prefix, 'include')]
         self.library_dirs = ['brianlib/randomkit']
-        if sys.platform == 'win32':
-            self.library_dirs += [os.path.join(sys.prefix, 'Library', 'Lib')]
-        else:
-            self.library_dirs += [os.path.join(sys.prefix, 'lib')]
         self.runtime_library_dirs = []
-        if sys.platform.startswith('linux'):
-            self.runtime_library_dirs += [os.path.join(sys.prefix, 'lib')]
         self.run_environment_variables = {}
         if sys.platform.startswith('darwin'):
             if 'DYLD_LIBRARY_PATH' in os.environ: