Split some overly long lines

src/items/functions.md

@@ -46,10 +46,13 @@ A _function_ consists of a [block] (that's the _body_ of the function),
 along with a name, a set of parameters, and an output type.
 Other than a name, all these are optional.
 Functions are declared with the keyword `fn`.
-Functions may declare a set of *input* [*variables*][variables] as parameters, through which the caller passes arguments into the function, and the *output* [*type*][type] of the value the function will return to its caller on completion.
+Functions may declare a set of *input* [*variables*][variables] as parameters,
+through which the caller passes arguments into the function, and the *output*
+[*type*][type] of the value the function will return to its caller on completion.
 If the output type is not explicitly stated, it is the [unit type].
 
-When referred to, a _function_ yields a first-class *value* of the corresponding zero-sized [*function item type*], which when called evaluates to a direct call to the function.
+When referred to, a _function_ yields a first-class *value* of the corresponding
+zero-sized [*function item type*], which when called evaluates to a direct call to the function.
 
 For example, this is a simple function:
 ```rust