Question

在以下代码中：

float sfrand( int *seed )
{
    float res;

    seed[0] *= 16807;

    *((unsigned int *) &res) = ( ((unsigned int)seed[0])>>9 ) | 0x40000000;

    return( res-3.0f );
}

来源：http://iquilezles.org/www/articles/sfrand/sfrand.htm

Answer 1

seed[0]与*seed相同，它是seed指针指向的第一个整数（如果不指向数组，则可能是唯一的整数）。

*=运算符是“按产品分配”运算符，

seed[0] *= 16807;与

相同

*seed = *seed * 16807;，这是您要查询的行的内容。

看来，整个函数是一种生成伪随机数的简单算法。修改种子的目的是，下一次调用将产生一个不同的伪随机数。

Answer 2

public class PrefabReplace : EditorWindow { [SerializeField] private GameObject _prefab; private bool _selectionChanged; private string _objectsToSearch = ""; private List<GameObject> _foundObjects = new List<GameObject>(); private readonly GUIStyle _guiStyle = new GUIStyle(); //create a new variable private int _count; private bool _addFoundObjects; private bool _keepNames = true; private bool _keepPlaceInHierarchy = true; private static GameObject _newObject; private static Component[] _components; [MenuItem("Tools/Prefab Replace")] private static void CreateReplaceWithPrefab() { const int width = 340; const int height = 600; var x = (Screen.currentResolution.width - width) / 2; var y = (Screen.currentResolution.height - height) / 2; GetWindow<PrefabReplace>().position = new Rect(x, y, width, height); } private void OnGUI() { _guiStyle.fontSize = 15; //change the font size Searching(); GUILayout.Space(10); Replacing(); GUILayout.Space(50); Settings(); } private void Searching() { //GUI.Label(new Rect(10, 15, 150, 20), "Search by name", guiStyle); _objectsToSearch = GUI.TextField(new Rect(90, 35, 150, 20), _objectsToSearch, 25); if (_objectsToSearch != "") { GUI.enabled = true; } else { GUI.enabled = false; _count = 0; } GUILayout.Space(15); if (GUILayout.Button("Search")) { _foundObjects = new List<GameObject>(); _count = 0; foreach (var gameObj in FindObjectsOfType<GameObject>().Where(gameObj => gameObj.name == _objectsToSearch)) { _count += 1; _foundObjects.Add(gameObj); foreach (Transform child in gameObj.transform) { _count += 1; _foundObjects.Add(child.gameObject); } } if (_foundObjects.Count == 0) { _count = 0; } } GUI.enabled = true; EditorGUI.LabelField(new Rect(90, 65, 210, 15), "Number of found objects and childs"); GUI.TextField(new Rect(90, 80, 60, 15), _count.ToString(), 25); GUILayout.Space(100); GUI.enabled = _count > 0; if (GUILayout.Button("Replace found objects")) { if (_prefab != null) { InstantiatePrefab(_foundObjects); } } GUI.enabled = true; } private void Replacing() { GUILayout.Space(20); GUILayout.BeginVertical(GUI.skin.box); GUILayout.Label("Replacing"); GUILayout.Space(20); _prefab = (GameObject)EditorGUILayout.ObjectField("Prefab", _prefab, typeof(GameObject), false); var selection = Selection.objects.OfType<GameObject>().ToList(); if (_selectionChanged) { if (selection.Count == 0) { GUI.enabled = false; } for (var i = selection.Count - 1; i >= 0; --i) { var selectedObject = selection[i]; if (_prefab != null && selection.Count > 0 && selectedObject.scene.name != null && _prefab != PrefabUtility .GetCorrespondingObjectFromSource(selectedObject)) { GUI.enabled = true; } else { GUI.enabled = false; } } } else { GUI.enabled = false; } if (GUILayout.Button("Replace")) { InstantiatePrefab(selection); _selectionChanged = false; } GUILayout.Space(10); GUI.enabled = true; EditorGUILayout.LabelField("Selection count: " + Selection.objects.OfType<GameObject>().Count()); GUILayout.EndVertical(); } private void Settings() { _keepPlaceInHierarchy = GUILayout.Toggle(_keepPlaceInHierarchy, "Keep order place in hierarchy"); _keepNames = GUILayout.Toggle(_keepNames, "Keep names"); } private void OnInspectorUpdate() { Repaint(); } private void OnSelectionChange() { _selectionChanged = true; } private void InstantiatePrefab(IReadOnlyList<GameObject> selection) { if (_prefab == null || selection.Count <= 0) return; for (var i = selection.Count - 1; i >= 0; --i) { var selected = selection[i]; _components = selected.GetComponents(typeof(MonoBehaviour)); //if (components.Length == 0) //{ SceneManager.SetActiveScene(SceneManager.GetSceneByName(selected.scene.name)); var prefabType = PrefabUtility.GetPrefabAssetType(_prefab); //GameObject newObject; if (prefabType == PrefabAssetType.Regular) { _newObject = (GameObject)PrefabUtility.InstantiatePrefab(_prefab); } else { _newObject = Instantiate(_prefab); if (_keepNames == false) { _newObject.name = _prefab.name; } } if (_newObject == null) { Debug.LogError("Error instantiating prefab"); break; } Undo.RegisterCreatedObjectUndo(_newObject, "Replace With Prefabs"); _newObject.transform.parent = selected.transform.parent; _newObject.transform.localPosition = selected.transform.localPosition; _newObject.transform.localRotation = selected.transform.localRotation; _newObject.transform.localScale = selected.transform.localScale; if (_keepPlaceInHierarchy) { _newObject.transform.SetSiblingIndex(selected.transform.GetSiblingIndex()); } if (_keepNames) { _newObject.name = selected.name; } foreach (var comp in _components) { _newObject.Init(comp); } Undo.DestroyObjectImmediate(selected); //} } } }行只是seed[0] *= 16807;

的快捷方式

以下是类似结构的列表：https://www.programiz.com/c-programming/c-operators

Answer 3

*=是乘法的复合运算符。在此运算符中，左操作数与右操作数相乘的结果将与左操作数一起存储。因此，在此语句seed[0] *= 1680;中，左操作数为seed [0]，右操作数为1680。执行该语句后，seed[0]将等于seed[0] * 1680。与此类似：

 seed[0] = seed[0] * 1680;

我们有一些复合运算符：+=，-=，/=，...以相同的行为工作。

该行seed [0] * = 16807有什么作用

3 个答案: