diff --git a/CHANGELOG b/CHANGELOG
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,8 @@
+2024-09-07
+        * Version bump (4.0). (#532)
+        * Update example to demonstrate struct update support. (#524)
+        * Update example to demonstrate array update support. (#36)
+
 2024-07-07
         * Version bump (3.20). (#522)
         * Update README to reflect support for GHC 9.8. (#518)
diff --git a/copilot.cabal b/copilot.cabal
--- a/copilot.cabal
+++ b/copilot.cabal
@@ -1,5 +1,5 @@
 name:                copilot
-version:             3.20
+version:             4.0
 cabal-version:       >= 1.10
 license:             BSD3
 license-file:        LICENSE
@@ -52,12 +52,12 @@
                      , directory             >= 1.3  && < 1.4
                      , filepath              >= 1.4  && < 1.5
 
-                     , copilot-core          >= 3.20 && < 3.21
-                     , copilot-theorem       >= 3.20 && < 3.21
-                     , copilot-language      >= 3.20 && < 3.21
-                     , copilot-libraries     >= 3.20 && < 3.21
-                     , copilot-c99           >= 3.20 && < 3.21
-                     , copilot-prettyprinter >= 3.20 && < 3.21
+                     , copilot-core          >= 4.0 && < 4.1
+                     , copilot-theorem       >= 4.0 && < 4.1
+                     , copilot-language      >= 4.0 && < 4.1
+                     , copilot-libraries     >= 4.0 && < 4.1
+                     , copilot-c99           >= 4.0 && < 4.1
+                     , copilot-prettyprinter >= 4.0 && < 4.1
 
 
     exposed-modules: Language.Copilot, Language.Copilot.Main
diff --git a/examples/Array.hs b/examples/Array.hs
--- a/examples/Array.hs
+++ b/examples/Array.hs
@@ -26,7 +26,21 @@
   -- It passes the current value of arr as an argument.
   -- The prototype of 'func' would be:
   -- void func (int8_t arg[3]);
-  trigger "func" (arr .!! 0) [arg arr]
+  trigger "func" (arr ! 0) [arg arr]
+
+  -- A trigger that fires 'func2' every time.
+  -- It passes the current value of arr as an argument, but updating the first
+  -- element of the array to always be True.
+  -- The prototype of 'func2' would be:
+  -- void func2 (int8_t arg[3]);
+  trigger "func2" true [arg (arr !! 0 =: true)]
+
+  -- A trigger that fires 'func2' every time.
+  -- It passes the current value of arr as an argument, but negating the second
+  -- element of the array.
+  -- The prototype of 'func3' would be:
+  -- void func3 (int8_t arg[3]);
+  trigger "func3" true [arg (arr !! 1 =$ not)]
 
 -- Compile the spec
 main :: IO ()
diff --git a/examples/Structs.hs b/examples/Structs.hs
--- a/examples/Structs.hs
+++ b/examples/Structs.hs
@@ -56,13 +56,13 @@
   -- Check equality, indexing into nested structs and arrays. Note that this is
   -- trivial by equality.
   trigger "equalitySameIndex"
-    ((((battery#volts) .!! 0)#numVolts) == (((battery#volts) .!! 0)#numVolts))
+    ((((battery#volts) ! 0)#numVolts) == (((battery#volts) ! 0)#numVolts))
     [arg battery]
 
   -- Same as previous example, but get a different array index (so should be
   -- false).
   trigger "equalityDifferentIndices"
-    ((((battery#other) .!! 2) .!! 3) == (((battery#other) .!! 2) .!! 4))
+    ((((battery#other) ! 2) ! 3) == (((battery#other) ! 2) ! 4))
     [arg battery]
 
 main :: IO ()
diff --git a/examples/what4/Structs.hs b/examples/what4/Structs.hs
--- a/examples/what4/Structs.hs
+++ b/examples/what4/Structs.hs
@@ -57,12 +57,16 @@
   -- Check equality, indexing into nested structs and arrays. Note that this is
   -- trivial by equality.
   void $ prop "Example 1" $ forAll $
-    (((battery#volts) .!! 0)#numVolts) == (((battery#volts) .!! 0)#numVolts)
+    (((battery#volts) ! 0)#numVolts) == (((battery#volts) ! 0)#numVolts)
 
   -- Same as previous example, but get a different array index (so should be
   -- false).
   void $ prop "Example 2" $ forAll $
-    (((battery#other) .!! 2) .!! 3) == (((battery#other) .!! 2) .!! 4)
+    (((battery#other) ! 2) ! 3) == (((battery#other) ! 2) ! 4)
+
+  -- Update a struct field, then check it for equality.
+  void $ prop "Example 3" $ forAll $
+    ((battery ## temp =$ (+1))#temp == (battery#temp + 1))
 
 main :: IO ()
 main = do