On Fri, Oct 19, 2018 at 12:36 PM Ian Lance Taylor <[email protected]> wrote:
>
> On Thu, Oct 18, 2018 at 10:48 AM, Burak Serdar <[email protected]> wrote:
> > On Thu, Oct 18, 2018 at 11:35 AM Ian Lance Taylor <[email protected]> wrote:
> >>
> >> On Wed, Oct 17, 2018 at 11:58 AM, Burak Serdar <[email protected]> wrote:
> >> >
> >> > Instead of specifying the minimal set of operations a type should
> >> > satisfy, why not describe what the type should look like:
> >> >
> >> > func f(in like T)
> >>
> >> I don't see how this approach can handle multiple types that need to
> >> work together in some known way, like the Graph/Node/Edge case in the
> >> design draft.
> >
> >
> > Still discussing the details, but the graph case in the design draft
> > can look like this:
> >
> > type Node like interface {
> > Edges() []Edge
> > }
> >
> > type Edge like interface {
> > Nodes() (Node,Node)
> > }
> >
> > type Graph like struct {
> > Nodes []*Node
> > }
> >
> > func New(nodes []*Node) *Graph {
> > return &Graph{Nodes:nodes}
> > }
> >
> >
> > The instantiation:
> >
> > type MyNode struct {...}
> >
> > func (m MyNode) Edges() []MyEdge {...}
> >
> > type MyEdge struct { ...}
> >
> > func (e MyEdge) Nodes() (*MyNode,*MyNode) {...}
> >
> > type MyGraph graph.Graph {
> > Nodes []*MyNodes
> > }
> >
> > x:=graph.New(MyGraph)(myNodes)
>
> Thanks. I note the subtlety whereby the name Edge in the generic code
> gets attached to the name MyEdge in the non-generic code, although it
> does not appear anywhere in the call to graph.New. There is a type
> mapping happening somewhere.
This is still work in progress, but:
graph.New(MyGraph)(myNodes) maps MyGraph to graph.Graph. From
MyGraph.Nodes, MyNode (not MyNodes, there is a typo in the example)
maps to graph.Node, and from MyNode.Edges(), MyEdge maps to
graph.Edge.
I wrote
type MyGraph graph.Graph {
}
for the declaration of the MyGraph type as an instantiation of the
template graph.Graph, and that also could be used for the same type
inference.
>
> Ian
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