···

       
145
       
145
       
 
       
    in fix g

     

       
146
       
146
       
 
       
    ```

     

       
147
       
147
       
 
       


     

       
148
       
148
       
+
       
    :::{.note}

     

       
149
       
149
       
+
       
    The argument to the given fixed-point function after applying an overlay will *not* refer to its own return value, but rather to the value after evaluating the overlay function.

     

       
150
       
150
       
+
       


     

       
151
       
151
       
+
       
    The given fixed-point function is called with a separate argument than if it was evaluated with `lib.fix`.

     

       
152
       
152
       
+
       
    :::

     

       
153
       
153
       
+
       


     

       
148
       
154
       
 
       
    :::{.example}

     

       
149
       
155
       
 
       


     

       
150
       
156
       
 
       
    # Extend a fixed-point function with an overlay

     
···

       
230
       
236
       
 
       


     

       
231
       
237
       
 
       
      fix (extends (final: prev: { c = final.a + final.b; }) f)

     

       
232
       
238
       
 
       
      => { a = 1; b = 3; c = 4; }

     

       
233
       
233
       
-
       


     

       
234
       
234
       
-
       
    :::{.note}

     

       
235
       
235
       
-
       
    The argument to the given fixed-point function after applying an overlay will *not* refer to its own return value, but rather to the value after evaluating the overlay function.

     

       
236
       
236
       
-
       


     

       
237
       
237
       
-
       
    The given fixed-point function is called with a separate argument than if it was evaluated with `lib.fix`.

     

       
238
       
238
       
-
       
    The new argument

     

       
239
       
239
       
-
       
    :::

     

       
240
       
239
       
 
       
  */

     

       
241
       
240
       
 
       
  extends =

     

       
242
       
241
       
 
       
    # The overlay to apply to the fixed-point function