Go Generics and a Binary Tree

generics.go

package main

import (
	"fmt"
)

// BinaryNode is the placeholder for a number
type BinaryNode[T NumberType] struct {
	value T
	left  *BinaryNode[T]
	right *BinaryNode[T]
}

type BinaryTree[T NumberType] struct {
	root *BinaryNode[T]
}

// NumberType is the constraint on the type of Number
// In case T is not a valid constraint, the program will not compile
type NumberType interface {
	int32 | int64 | float32 | float64
}

// getValue is the generic function that returns the value of a Number
func (n *BinaryNode[T]) getValue() T {
	return n.value
}

// InsertNode is the generic function that inserts a Node into a BinaryTree
func (t *BinaryTree[T]) InsertNode(n BinaryNode[T]) *BinaryTree[T] {
	if t.root == nil {
		t.root = &BinaryNode[T]{value: n.getValue()}
	} else {
		t.root.insert(n.getValue())
	}

	return t
}

// insert is the generic function that inserts a value into a BinaryTree
func (n *BinaryNode[T]) insert(value T) {
	if n == nil {
		return
	}
	if value <= n.getValue() {
		if n.left == nil {
			n.left = &BinaryNode[T]{value: value} // Already the correct type
		} else {
			n.left.insert(value)
		}
	} else {
		if n.right == nil {
			n.right = &BinaryNode[T]{value: value} // Already the correct type
		} else {
			n.right.insert(value)
		}
	}
}

func (n *BinaryNode[T]) print(ns int, ch rune) {
	if n == nil {
		return
	}
	for i := 0; i < ns; i++ {
		fmt.Printf(" ")
	}

	fmt.Printf("%c:%v\n", ch, n.getValue())
	n.left.print(ns+1, 'l')
	n.right.print(ns+1, 'r')
}

func main() {
	tree := &BinaryTree[int64]{}
	tree.InsertNode(BinaryNode[int64]{value: 10})
	tree.InsertNode(BinaryNode[int64]{value: 20})
	tree.InsertNode(BinaryNode[int64]{value: 30})
	tree.InsertNode(BinaryNode[int64]{value: 3})
	tree.InsertNode(BinaryNode[int64]{value: 2})
	tree.InsertNode(BinaryNode[int64]{value: 1})
	tree.root.print(0, 'R')

	treeFloat := &BinaryTree[float64]{}
	treeFloat.InsertNode(BinaryNode[float64]{value: 11.11})
	treeFloat.InsertNode(BinaryNode[float64]{value: 22.22})
	treeFloat.InsertNode(BinaryNode[float64]{value: 33.33})
	treeFloat.InsertNode(BinaryNode[float64]{value: 0.1})
	treeFloat.root.print(0, 'R')
}