Johannes <[email protected]> writes:
Hi Johannes,
> I am trying to build an alternative record building macro. For example
>
> (define-record point [x y])
> should define
> - a new type point
> - a constructor make-point
(defrecord Point [x y]) generates also a constructor function (->Point x
y).
> - a type checker point?
As a shorthand for (instance? Point my-obj)? Well, that could make
sense here and there, although in general, if you use those type-checks
like
(cond
(Point? o) (transform-point o)
(Polygon? o) (transform-polygon o)
...)
it's likely that you want a protocol Transformable declaring a
`transform` method, and both Point and Polygon provide an implementation
for it. Then the above becomes just (transform o), and it'll do the
right thing no matter if it's a Point or Polygon.
> - and 2 getters point-x and point-y
I don't see a benefit of (point-x point) over (:x point).
The main problem with your `define-point` macro is that it should also
allow for defining protocol implementations like `defrecord`. Else,
it's simply not as powerful as the latter.
Bye,
Tassilo
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