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package unstable
// root contains a full AST.
//
// It is immutable once constructed with Builder.
type root struct {
nodes []Node
}
// Iterator over the top level nodes.
func (r *root) Iterator() Iterator {
it := Iterator{}
if len(r.nodes) > 0 {
it.node = &r.nodes[0]
}
return it
}
func (r *root) at(idx reference) *Node {
return &r.nodes[idx]
}
type reference int
const invalidReference reference = -1
func (r reference) Valid() bool {
return r != invalidReference
}
type builder struct {
tree root
lastIdx int
}
func (b *builder) Tree() *root {
return &b.tree
}
func (b *builder) NodeAt(ref reference) *Node {
return b.tree.at(ref)
}
func (b *builder) Reset() {
b.tree.nodes = b.tree.nodes[:0]
b.lastIdx = 0
}
func (b *builder) Push(n Node) reference {
b.lastIdx = len(b.tree.nodes)
b.tree.nodes = append(b.tree.nodes, n)
return reference(b.lastIdx)
}
func (b *builder) PushAndChain(n Node) reference {
newIdx := len(b.tree.nodes)
b.tree.nodes = append(b.tree.nodes, n)
if b.lastIdx >= 0 {
b.tree.nodes[b.lastIdx].next = newIdx - b.lastIdx
}
b.lastIdx = newIdx
return reference(b.lastIdx)
}
func (b *builder) AttachChild(parent reference, child reference) {
b.tree.nodes[parent].child = int(child) - int(parent)
}
func (b *builder) Chain(from reference, to reference) {
b.tree.nodes[from].next = int(to) - int(from)
}
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