Expressions in Go

apt.go

type Node interface {
	Eval(x, y float32) float32
	String() string
	SetParent(parent Node)
	GetParent() Node
	GetChildren() []Node
	SetChildren([]Node)
	AddRandom(node Node)
	AddLeaf(leaf Node) bool
	NodeCount() int
}


type BaseNode struct {
	Parent   Node
	Children []Node
}

func (node *BaseNode) SetParent(parent Node) {
	node.Parent = parent
}

//and so on so BaseNode satisfies the whole interface


//Then create a struct for each operation, or constant
type OpPlus struct {
	BaseNode
}

//A constructor which forces the size of the children slice to be correct
func NewOpPlus() *OpPlus {
	return &OpPlus{BaseNode{nil, make([]Node, 2)}}
}

// Then each operation must implement eval and string, the other interface
// functions are satisfied by the BaseNode embedded in the type
func (op *OpPlus) Eval(x, y float32) float32 {
	return op.Children[0].Eval(x, y) + op.Children[1].Eval(x, y)
}

func (op *OpPlus) String() string {
	return "( + " + op.Children[0].String() + " " + op.Children[1].String() + " )"
}