jyapayne/patty
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Added constructors

Browse source
This commit is contained in:
Andrea Ferretti 2015-07-02 21:09:58 +02:00
commit d3b7711cd1
3 changed files with 84 additions and 15 deletions
Download patch file Download diff file Expand all files Collapse all files

23
README.md
View file

@ -86,25 +86,36 @@ and expands to
```nim
type
ShapeKind = enum
ShapeE = enum
Circle, Rectangle
Shape = object
case kind: ShapeKind
of Circle:
case kind: ShapeE
of CircleE:
r: float
of Rectangle:
of RectangleE:
w: float
h: float
of UnitCircle:
of UnitCircleE:
nil
proc Circle(r: float; x: float; y: float): Shape =
Shape(kind: CircleE, r: r)
proc Rectangle(w: float; h: float): Shape =
Shape(kind: RectangleE, w: w, h: h)
proc UnitCircle(side: int): Shape =
Shape(kind: UnitCircleE)
```
Notice that the macro also generates three convenient constructors (`Circle` ,`Rectangle` and `UnitCircle`), and in fact the names in the enum are `CircleE`, `RectangleE` and `UnitCircleE` to avoid a name conflict.
A couple of limitations fo the `adt` macro:
* field names must be unique across branches (that is, different variants cannot have two fields with the same name). This is actually a limitation of Nim.
* the shortcut that groups field names by type does not seem to work, that is, in the above example one could not write `Rectangle(w, h: float)`.
In the future, Patty will also add a proper definition of equality and generated contructors.
In the future, Patty will also add a proper definition of equality.
Things that do not work (yet)
-----------------------------