On Fri, Oct 19, 2018 at 10:48 AM alanfo <[email protected]> wrote:
> In the light of all the feedback there's been, I've put together a
> proposal which sticks closely to the original design and only changes what
> most people consider needs to be changed in some way. Some recent ideas
> which seemed plausible but which I felt had little chance of adoption have
> been rejected.
>
> https://gist.github.com/alanfo/72f07362d687f625a958bde1808e0c87
>
I like your simplified syntax for contracts, but I would prefer to see
contracts specify one type at a time, rather than several. I think this
will be easier for people to understand when type parameters are
independent or have only one-way dependencies, and that this case will be
much more command than the case of mutual dependencies. A suitable syntax
might be something like
contract Addable {
// Note: using the contract name to represent the type being described
Addable + Addable
}
func SliceSum[type T](s []T) T {
var sum T
for _, t := range s {
sum = sum + t
}
}
contract List[type T] {
func (List) Len() int
func (List) At(int) T
}
func ListSum[type L List[T], T Addable](l L) T {
var sum T
for n := 0; n < l.Len(); n++ {
sum = sum + l.At(n)
}
}
contract Comparable {
func (Comparable) Equal(Comparable) bool
}
contract Hashable {
Comparable // embedding
func (Comparable) Hash() uint64
}
// An associative array using user-defined notions of equality and hashing
type Map[type K Hashable, V] struct { ... }
contract NodeType[type E] {
func (NodeType) Edges() []E
}
contract EdgeType[type N] {
func (EdgeType) Nodes() (N, N)
}
type Graph[type N NodeType[E], type E EdgeType[N]] struct { ... }
This is somewhat like the "interfaces instead of contracts" proposals, but
without trying to force everything into interfaces. To enforce one type per
contract, we could have a rule that every line in a contract that is not an
embedding of another contract must explicitly use the contract name, and
the receiver type of a method must be either ContractName or *ContractName.
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