From 5237d3f115c76d7b148105571e12805b2b04ab68 Mon Sep 17 00:00:00 2001
From: Jordan Lees <jordanlees@mailbox.org>
Date: Fri, 30 Jun 2023 17:01:06 -0700
Subject: [PATCH 1/2] Fixed typos so that the scala code can be pasted into a
 project & it runs

---
 docs/Advanced-Concepts/CDEs.rst | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/docs/Advanced-Concepts/CDEs.rst b/docs/Advanced-Concepts/CDEs.rst
index a4a19966..4805310f 100644
--- a/docs/Advanced-Concepts/CDEs.rst
+++ b/docs/Advanced-Concepts/CDEs.rst
@@ -21,18 +21,18 @@ Consider the following example using CDEs.
 
     class WithX(b: Boolean) extends Config((site, here, up) => {
       case SomeKeyX => b
-    }
+    })
 
     class WithY(b: Boolean) extends Config((site, here, up) => {
       case SomeKeyY => b
-    }
+    })
 
 
 When forming a query based on a ``Parameters`` object, like ``p(SomeKeyX)``, the configuration system traverses the "chain" of config fragments until it finds a partial function which is defined at the key, and then returns that value.
 
 .. code:: scala
 
-    val params = Config(new WithX(true) ++ new WithY(true)) // "chain" together config fragments
+    val params = new Config(new WithX(true) ++ new WithY(true)) // "chain" together config fragments
     params(SomeKeyX) // evaluates to true
     params(SomeKeyY) // evaluates to true
     params(SomeKeyZ) // evaluates to false
@@ -54,10 +54,10 @@ Site
 
     class WithXEqualsYSite extends Config((site, here, up) => {
       case SomeKeyX => site(SomeKeyY) // expands to site(SomeKeyY, site)
-    }
+    })
 
-    val params_1 = Config(new WithXEqualsYSite ++ new WithY(true))
-    val params_2 = Config(new WithY(true) ++ new WithXEqualsYSite)
+    val params_1 = new Config(new WithXEqualsYSite ++ new WithY(true))
+    val params_2 = new Config(new WithY(true) ++ new WithXEqualsYSite)
     params_1(SomeKeyX) // evaluates to true
     params_2(SomeKeyX) // evaluates to true
 
@@ -75,10 +75,10 @@ Here
     class WithXEqualsYHere extends Config((site, here, up) => {
       case SomeKeyY => false
       case SomeKeyX => here(SomeKeyY, site)
-    }
+    })
 
-    val params_1 = Config(new WithXEqualsYHere ++ new WithY(true))
-    val params_2 = Config(new WithY(true) ++ new WithXEqualsYHere)
+    val params_1 = new Config(new WithXEqualsYHere ++ new WithY(true))
+    val params_2 = new Config(new WithY(true) ++ new WithXEqualsYHere)
 
     params_1(SomeKeyX) // evaluates to false
     params_2(SomeKeyX) // evaluates to false
@@ -95,10 +95,10 @@ Up
 
     class WithXEqualsYUp extends Config((site, here, up) => {
       case SomeKeyX => up(SomeKeyY, site)
-    }
+    })
 
-    val params_1 = Config(new WithXEqualsYUp ++ new WithY(true))
-    val params_2 = Config(new WithY(true) ++ new WithXEqualsYUp)
+    val params_1 = new Config(new WithXEqualsYUp ++ new WithY(true))
+    val params_2 = new Config(new WithY(true) ++ new WithXEqualsYUp)
 
     params_1(SomeKeyX) // evaluates to true
     params_2(SomeKeyX) // evaluates to false

From 487009181e53413a1f678eefa6d1b41e441717d9 Mon Sep 17 00:00:00 2001
From: Jordan Lees <jordanlees@mailbox.org>
Date: Fri, 30 Jun 2023 17:15:24 -0700
Subject: [PATCH 2/2] Added details on how properties can be overridden

---
 docs/Advanced-Concepts/CDEs.rst | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/docs/Advanced-Concepts/CDEs.rst b/docs/Advanced-Concepts/CDEs.rst
index 4805310f..a609a8c5 100644
--- a/docs/Advanced-Concepts/CDEs.rst
+++ b/docs/Advanced-Concepts/CDEs.rst
@@ -39,6 +39,19 @@ When forming a query based on a ``Parameters`` object, like ``p(SomeKeyX)``, the
 
 In this example, the evaluation of ``params(SomeKeyX)`` will terminate in the partial function defined in ``WithX(true)``, while the evaluation of ``params(SomeKeyY)`` will terminate in the partial function defined in ``WithY(true)``. Note that when no partial functions match, the evaluation will return the default value for that parameter.
 
+Config fragments take precedence from left to right, meaning that a fragment at the start of the chain can override the value of a fragment to the right. It helps to read the fragment chain from right to left.
+
+.. code:: scala
+
+    case object SomeKeyX extends Field[Int](0)
+
+    class WithX(n: Int) extends Config((site, here, up) => {
+      case SomeKeyX => n
+    })
+
+    val params = new Config(new WithX(10) ++ new WithX(5))
+    println(params(SomeKeyX)) // evaluates to 10
+
 The real power of CDEs arises from the ``(site, here, up)`` parameters to the partial functions, which provide useful "views" into the global parameterization that the partial functions may access to determine a parameterization.
 
 .. note::