Initial commit: Go 1.23 release state

test/typeparam/graph.go

@@ -0,0 +1,231 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"errors"
+	"fmt"
+)
+
+// _SliceEqual reports whether two slices are equal: the same length and all
+// elements equal. All floating point NaNs are considered equal.
+func _SliceEqual[Elem comparable](s1, s2 []Elem) bool {
+	if len(s1) != len(s2) {
+		return false
+	}
+	for i, v1 := range s1 {
+		v2 := s2[i]
+		if v1 != v2 {
+			isNaN := func(f Elem) bool { return f != f }
+			if !isNaN(v1) || !isNaN(v2) {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+// A Graph is a collection of nodes. A node may have an arbitrary number
+// of edges. An edge connects two nodes. Both nodes and edges must be
+// comparable. This is an undirected simple graph.
+type _Graph[_Node _NodeC[_Edge], _Edge _EdgeC[_Node]] struct {
+	nodes []_Node
+}
+
+// _NodeC is the constraints on a node in a graph, given the _Edge type.
+type _NodeC[_Edge any] interface {
+	comparable
+	Edges() []_Edge
+}
+
+// _EdgeC is the constraints on an edge in a graph, given the _Node type.
+type _EdgeC[_Node any] interface {
+	comparable
+	Nodes() (a, b _Node)
+}
+
+// _New creates a new _Graph from a collection of Nodes.
+func _New[_Node _NodeC[_Edge], _Edge _EdgeC[_Node]](nodes []_Node) *_Graph[_Node, _Edge] {
+	return &_Graph[_Node, _Edge]{nodes: nodes}
+}
+
+// nodePath holds the path to a node during ShortestPath.
+// This should ideally be a type defined inside ShortestPath,
+// but the translator tool doesn't support that.
+type nodePath[_Node _NodeC[_Edge], _Edge _EdgeC[_Node]] struct {
+	node _Node
+	path []_Edge
+}
+
+// ShortestPath returns the shortest path between two nodes,
+// as an ordered list of edges. If there are multiple shortest paths,
+// which one is returned is unpredictable.
+func (g *_Graph[_Node, _Edge]) ShortestPath(from, to _Node) ([]_Edge, error) {
+	visited := make(map[_Node]bool)
+	visited[from] = true
+	workqueue := []nodePath[_Node, _Edge]{nodePath[_Node, _Edge]{from, nil}}
+	for len(workqueue) > 0 {
+		current := workqueue
+		workqueue = nil
+		for _, np := range current {
+			edges := np.node.Edges()
+			for _, edge := range edges {
+				a, b := edge.Nodes()
+				if a == np.node {
+					a = b
+				}
+				if !visited[a] {
+					ve := append([]_Edge(nil), np.path...)
+					ve = append(ve, edge)
+					if a == to {
+						return ve, nil
+					}
+					workqueue = append(workqueue, nodePath[_Node, _Edge]{a, ve})
+					visited[a] = true
+				}
+			}
+		}
+	}
+	return nil, errors.New("no path")
+}
+
+type direction int
+
+const (
+	north direction = iota
+	ne
+	east
+	se
+	south
+	sw
+	west
+	nw
+	up
+	down
+)
+
+func (dir direction) String() string {
+	strs := map[direction]string{
+		north: "north",
+		ne:    "ne",
+		east:  "east",
+		se:    "se",
+		south: "south",
+		sw:    "sw",
+		west:  "west",
+		nw:    "nw",
+		up:    "up",
+		down:  "down",
+	}
+	if str, ok := strs[dir]; ok {
+		return str
+	}
+	return fmt.Sprintf("direction %d", dir)
+}
+
+type mazeRoom struct {
+	index int
+	exits [10]int
+}
+
+type mazeEdge struct {
+	from, to int
+	dir      direction
+}
+
+// Edges returns the exits from the room.
+func (m mazeRoom) Edges() []mazeEdge {
+	var r []mazeEdge
+	for i, exit := range m.exits {
+		if exit != 0 {
+			r = append(r, mazeEdge{
+				from: m.index,
+				to:   exit,
+				dir:  direction(i),
+			})
+		}
+	}
+	return r
+}
+
+// Nodes returns the rooms connected by an edge.
+//
+//go:noinline
+func (e mazeEdge) Nodes() (mazeRoom, mazeRoom) {
+	m1, ok := zork[e.from]
+	if !ok {
+		panic("bad edge")
+	}
+	m2, ok := zork[e.to]
+	if !ok {
+		panic("bad edge")
+	}
+	return m1, m2
+}
+
+// The first maze in Zork. Room indexes based on original Fortran data file.
+// You are in a maze of twisty little passages, all alike.
+var zork = map[int]mazeRoom{
+	11: {exits: [10]int{north: 11, south: 12, east: 14}}, // west to Troll Room
+	12: {exits: [10]int{south: 11, north: 14, east: 13}},
+	13: {exits: [10]int{west: 12, north: 14, up: 16}},
+	14: {exits: [10]int{west: 13, north: 11, east: 15}},
+	15: {exits: [10]int{south: 14}},                   // Dead End
+	16: {exits: [10]int{east: 17, north: 13, sw: 18}}, // skeleton, etc.
+	17: {exits: [10]int{west: 16}},                    // Dead End
+	18: {exits: [10]int{down: 16, east: 19, west: 18, up: 22}},
+	19: {exits: [10]int{up: 29, west: 18, ne: 15, east: 20, south: 30}},
+	20: {exits: [10]int{ne: 19, west: 20, se: 21}},
+	21: {exits: [10]int{north: 20}}, // Dead End
+	22: {exits: [10]int{north: 18, east: 24, down: 23, south: 28, west: 26, nw: 22}},
+	23: {exits: [10]int{east: 22, west: 28, up: 24}},
+	24: {exits: [10]int{ne: 25, down: 23, nw: 28, sw: 26}},
+	25: {exits: [10]int{sw: 24}}, // Grating room (up to Clearing)
+	26: {exits: [10]int{west: 16, sw: 24, east: 28, up: 22, north: 27}},
+	27: {exits: [10]int{south: 26}}, // Dead End
+	28: {exits: [10]int{east: 22, down: 26, south: 23, west: 24}},
+	29: {exits: [10]int{west: 30, nw: 29, ne: 19, south: 19}},
+	30: {exits: [10]int{west: 29, south: 19}}, // ne to Cyclops Room
+}
+
+func TestShortestPath() {
+	// The Zork maze is not a proper undirected simple graph,
+	// as there are some one way paths (e.g., 19 -> 15),
+	// but for this test that doesn't matter.
+
+	// Set the index field in the map. Simpler than doing it in the
+	// composite literal.
+	for k := range zork {
+		r := zork[k]
+		r.index = k
+		zork[k] = r
+	}
+
+	var nodes []mazeRoom
+	for idx, room := range zork {
+		mridx := room
+		mridx.index = idx
+		nodes = append(nodes, mridx)
+	}
+	g := _New[mazeRoom, mazeEdge](nodes)
+	path, err := g.ShortestPath(zork[11], zork[30])
+	if err != nil {
+		panic(fmt.Sprintf("%v", err))
+	}
+	var steps []direction
+	for _, edge := range path {
+		steps = append(steps, edge.dir)
+	}
+	want := []direction{east, west, up, sw, east, south}
+	if !_SliceEqual(steps, want) {
+		panic(fmt.Sprintf("ShortestPath returned %v, want %v", steps, want))
+	}
+}
+
+func main() {
+	TestShortestPath()
+}