The graph model could be a proper DAG

[jonathanhogg]

The graph model could be a proper DAG

[jonathanhogg]

OK. New plan for dealing with grafting.

Each Node has a weak-set of parents instead of a single parent pointer as now. Nodes that pop out of the top-level statement without any parent nodes are appended to the graph root, otherwise they are ignored – this way top-level queries work as before and there's no need for a new "discard" operator.

Instead of having a smash-append operator, have a stealing version of Query: so maybe {#foo} searches for tagged nodes, but {{#foo}} searches-for and removes the nodes from the place they are found. Note that this latter part is key if the node actually has multiple parents: {{#foo > #bar}} should only steal the #bar node from below the #foo node – it may still be parented somewhere else.

So our standard window shader graft could be:

{window}
    let contents={{window>*}}
    !shader fragment=read("feedback.frag")
        contents

This works, but is kinda ugly. A possible alternative is a delayed-append operator that builds the complete node before appending it to the parent, i.e., waits for the execute() generator to complete before appending the yielded results. Something like:

{window} ?
    !shader fragment=read("feedback.frag")
        {{window>*}}

[jonathanhogg]

Note that if I ditch queries, a la #17, then most of this is moot. In that case, references would need to stay so I might have to think a bit harder about whether they need to be improved / made more orthogonal.