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package ast
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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