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doc: Remove documentation on newtype enums.

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Patrick Walton 2013-03-07 18:15:07 -08:00
parent 7538450b8d
commit 1fcb0443cf
1 changed files with 36 additions and 44 deletions

80
doc/tutorial.md

@ -681,45 +681,6 @@ the value of `North` is 0, `East` is 1, `South` is 2, and `West` is 3.
When an enum is C-like, you can apply the `as` cast operator to
convert it to its discriminator value as an `int`.
<a name="single_variant_enum"></a>
There is a special case for enums with a single variant, which are
sometimes called "newtype-style enums" (after Haskell's "newtype"
feature). These are used to define new types in such a way that the
new name is not just a synonym for an existing type, but its own
distinct type: `type` creates a structural synonym, while this form of
`enum` creates a nominal synonym. If you say:
~~~~
enum GizmoId = int;
~~~~
That is a shorthand for this:
~~~~
enum GizmoId { GizmoId(int) }
~~~~
You can extract the contents of such an enum type with the
dereference (`*`) unary operator:
~~~~
# enum GizmoId = int;
let my_gizmo_id: GizmoId = GizmoId(10);
let id_int: int = *my_gizmo_id;
~~~~
Types like this can be useful to differentiate between data that have
the same type but must be used in different ways.
~~~~
enum Inches = int;
enum Centimeters = int;
~~~~
The above definitions allow for a simple way for programs to avoid
confusing numbers that correspond to different units.
For enum types with multiple variants, destructuring is the only way to
get at their contents. All variant constructors can be used as
patterns, as in this definition of `area`:
@ -789,10 +750,10 @@ match mytup {
## Tuple structs
Rust also has _nominal tuples_, which behave like both structs and tuples,
except that nominal tuple types have names
(so `Foo(1, 2)` has a different type from `Bar(1, 2)`),
and nominal tuple types' _fields_ do not have names.
Rust also has _tuple structs_, which behave like both structs and tuples,
except that, unlike tuples, tuple structs have names (so `Foo(1, 2)` has a
different type from `Bar(1, 2)`), and tuple structs' _fields_ do not have
names.
For example:
~~~~
@ -803,6 +764,37 @@ match mytup {
}
~~~~
<a name="newtype"></a>
There is a special case for tuple structs with a single field, which are
sometimes called "newtypes" (after Haskell's "newtype" feature). These are
used to define new types in such a way that the new name is not just a
synonym for an existing type but is rather its own distinct type.
~~~~
struct GizmoId(int);
~~~~
For convenience, you can extract the contents of such a struct with the
dereference (`*`) unary operator:
~~~~
# struct GizmoId(int);
let my_gizmo_id: GizmoId = GizmoId(10);
let id_int: int = *my_gizmo_id;
~~~~
Types like this can be useful to differentiate between data that have
the same type but must be used in different ways.
~~~~
struct Inches(int);
struct Centimeters(int);
~~~~
The above definitions allow for a simple way for programs to avoid
confusing numbers that correspond to different units.
# Functions
We've already seen several function definitions. Like all other static
@ -2294,7 +2286,7 @@ struct level. Note that fields and methods are _public_ by default.
pub mod farm {
# pub type Chicken = int;
# type Cow = int;
# enum Human = int;
# struct Human(int);
# impl Human { fn rest(&self) { } }
# pub fn make_me_a_farm() -> Farm { Farm { chickens: ~[], cows: ~[], farmer: Human(0) } }
pub struct Farm {