Update 'Functions and Methods'

Functions-and-Methods.md

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+Functions are written like this:
+
+```
+func ro someFunction
+	> input:Int
+	< output:Int:mut
+	---
+	somePhrase
+```
+
+The first part of the function's content is its inputs and outputs. A function
+may have any number of these, and they act as local variables. Function inputs
+must always be immutable, and function outputs must always be mutable.
+
+The second part is the actual code of the function. It is separated from the
+first part of the function with a separator token, and contains an indented
+block of phrases.
+
+To return data from a function, its outputs must be set as you would a normal
+variable.
+
+A function can be a method of an object if it lists the method receiver after
+an @ symbol:
+
+```
+func ro setGreeting
+	@ greeter:{Greeter}
+	> greeting
+	---
+	set greeter.greeting greeting
+```
+
+Method receivers, like inputs, must be immutable. They also must be pointers.
+It is important to note that if a pointer is immutable, the pointer cannot
+"move", but the data it points to can still be altered.
+
+Method receivers can be of any type defined in the same module except interface
+types.