From 8e8d5e0478efd90ee21115c45d78874208ddc0f7 Mon Sep 17 00:00:00 2001
From: Paul Romano <paul.k.romano@gmail.com>
Date: Mon, 24 Feb 2020 19:53:46 -0600
Subject: [PATCH] Documentation updates

---
 docs/source/io_formats/settings.rst        | 23 +++++++++++-----------
 examples/xml/custom_source/source_ring.cpp |  3 ++-
 openmc/source.py                           | 18 ++++++++++-------
 3 files changed, 25 insertions(+), 19 deletions(-)

diff --git a/docs/source/io_formats/settings.rst b/docs/source/io_formats/settings.rst
index 28754e7163..83aa0691f4 100644
--- a/docs/source/io_formats/settings.rst
+++ b/docs/source/io_formats/settings.rst
@@ -460,13 +460,13 @@ attributes/sub-elements:
     *Default*: None
 
   :library:
-    If this attribute is given, it indicates that the source is to be instanciated
-    from an externally compiled source function. This source can be as complex as
-    is required to define the source for your problem. The only requirement that
-    is made upon this source, is that there is a function called sample_source()
-    more documentation on how to build sources can be found in :ref:`custom_source`
+    If this attribute is given, it indicates that the source is to be
+    instantiated from an externally compiled source function. This source can be
+    as complex as is required to define the source for your problem. The only
+    requirement is that there is a function called ``sample_source()``. More
+    documentation on how to build sources can be found in :ref:`custom_source`.
 
-    *Deafult*: None
+    *Default*: None
 
   :space:
     An element specifying the spatial distribution of source sites. This element
@@ -645,8 +645,8 @@ more complicated sources.
 
   .. note:: You should only use the openmc::prn() random number generator
 
-In order to build your external source you need the following CMakeLists.txt
-file
+In order to build your external source, you will need to link it against the
+OpenMC shared library. This can be done by writing a CMakeLists.txt file:
 
 .. code-block:: cmake
 
@@ -656,9 +656,10 @@ file
    find_package(OpenMC REQUIRED HINTS <path to openmc>)
    target_link_libraries(source OpenMC::libopenmc)
 
-You will now have a libsource.so (or .dylib) file in this directory, now point
-the library attribute of the source XML element to this file and you will be
-able to sample particles.
+After running ``cmake`` and ``make``, you will have a libsource.so (or .dylib)
+file in your build directory. Setting the :attr:`openmc.Source.library`
+attribute to the path of this shared library will indicate that it should be
+used for sampling source particles at runtime.
 
 .. _univariate:
 
diff --git a/examples/xml/custom_source/source_ring.cpp b/examples/xml/custom_source/source_ring.cpp
index 0feb287022..d68122dd75 100644
--- a/examples/xml/custom_source/source_ring.cpp
+++ b/examples/xml/custom_source/source_ring.cpp
@@ -1,4 +1,5 @@
-#include <iostream>
+#include <cmath> // for M_PI
+
 #include "openmc/random_lcg.h"
 #include "openmc/source.h"
 #include "openmc/particle.h"
diff --git a/openmc/source.py b/openmc/source.py
index 339d41723e..7b709321f1 100644
--- a/openmc/source.py
+++ b/openmc/source.py
@@ -8,20 +8,22 @@ from openmc.stats.multivariate import UnitSphere, Spatial
 import openmc.checkvalue as cv
 
 
-class Source(object):
+class Source:
     """Distribution of phase space coordinates for source sites.
 
     Parameters
     ----------
-    space : openmc.stats.Spatial, optional
+    space : openmc.stats.Spatial
         Spatial distribution of source sites
-    angle : openmc.stats.UnitSphere, optional
+    angle : openmc.stats.UnitSphere
         Angular distribution of source sites
-    energy : openmc.stats.Univariate, optional
+    energy : openmc.stats.Univariate
         Energy distribution of source sites
-    filename : str, optional
+    filename : str
         Source file from which sites should be sampled
-    strength : Real
+    library : str
+        Path to a custom source library
+    strength : float
         Strength of the source
     particle : {'neutron', 'photon'}
         Source particle type
@@ -36,7 +38,9 @@ class Source(object):
         Energy distribution of source sites
     file : str or None
         Source file from which sites should be sampled
-    strength : Real
+    library : str or None
+        Path to a custom source library
+    strength : float
         Strength of the source
     particle : {'neutron', 'photon'}
         Source particle type