elmo full name

Author: bowbahdoe

src/classes/the_meaning_of_the_word_class.md

@@ -9,7 +9,7 @@ a `String` is classified by the set of things you can do to it and the data
 it stores. The `String` class would specify all of that.[^heady]
 
 
-[^idiot]: What an [idiot](https://www.shardcore.org/spx/2015/05/15/diogenes-and-the-chicken/)
+[^idiot]: What an [idiot](https://penelope.uchicago.edu/encyclopaedia_romana/greece/hetairai/diogenes.html)
 
 [^heady]: If that's a bit too heady of an explanation don't fret. You will likely get it intuitively eventually.
 There are like 50 different ways to explain it and eventually one will land for you.

src/floating_point_numbers/equality.md

@@ -29,6 +29,26 @@ IO.println(doesWhatYouExpect);
 ~}
 ```
 
+To account for that you can check if a number is "close enough" to another one
+by seeing if the "absolute value" of the difference is a small number.
+
+```java
+~void main() {
+double x = 0.1;
+double y = 0.2;
+// z will be 0.30000000000000004
+double z = x + y;
+
+double compare = 0.3;
+
+// this will be true.
+boolean doesWhatYouExpect = 
+    Math.abs(z - 0.3) < 0.00001;
+
+IO.println(doesWhatYouExpect);
+~}
+```
+
 A `double` can also be compared to an `int` and, if they represent the same value, they will be reported as equal.
 
 ```java

src/instance_methods/derived_values.md

@@ -21,4 +21,24 @@ void main() {
 }
 ```
 
-Which is useful for situations like where you store someones first and last name
+Which is useful for situations like where you store someones first and last name
+but need to ask "what is their full name?"
+
+```java
+class Elmo {
+    String firstName;
+    String lastName;
+
+    String fullName() {
+        return firstName + " " + lastName;
+    }
+}
+
+void main() {
+    Elmo elmo = new Elmo();
+    elmo.firstName = "Elmo";
+    elmo.lastName = "Furchester";
+
+    IO.println("Elmo's full name is " + elmo.fullName());
+}
+```