means that you, as the programmer, must handle the case when an `Option<T>` is
`None` instead of `Some(t)`.
-But wait, what about `unwrap` used in [`unwrap-double`](#code-unwrap-double)?
+But wait, what about `unwrap`,which we used [`previously`](#code-unwrap-double)?
There was no case analysis there! Instead, the case analysis was put inside the
`unwrap` method for you. You could define it yourself if you want:
### Composing `Option<T>` values
-In [`option-ex-string-find`](#code-option-ex-string-find)
+In an [example from before](#code-option-ex-string-find),
we saw how to use `find` to discover the extension in a file name. Of course,
not all file names have a `.` in them, so it's possible that the file name has
no extension. This *possibility of absence* is encoded into the types using