是指针的变量数组还是指向数组的指针？

Question

我学习C语言，我很难理解指针和数组。

在我阅读的教程中，我有这一行：

 char* arrP1[] = { "father","mother",NULL }; 

我的问题是什么是arrP1？

是指向静态字符串的指针数组：

或者它是指向字符串数组的指针：

我很困惑......什么是arrP1？

Answer 1

TypeErrorTraceback (most recent call last) <ipython-input-5-cf75ce057c42> in <module>() ----> 1 df.reindex(index = 'timestamp') /opt/conda/envs/python2/lib/python2.7/site-packages/pandas/core/frame.pyc in reindex(self, index, columns, **kwargs) 2731 def reindex(self, index=None, columns=None, **kwargs): 2732 return super(DataFrame, self).reindex(index=index, columns=columns, -> 2733 **kwargs) 2734 2735 @Appender(_shared_docs['reindex_axis'] % _shared_doc_kwargs) /opt/conda/envs/python2/lib/python2.7/site-packages/pandas/core/generic.pyc in reindex(self, *args, **kwargs) 2513 # perform the reindex on the axes 2514 return self._reindex_axes(axes, level, limit, tolerance, method, -> 2515 fill_value, copy).__finalize__(self) 2516 2517 def _reindex_axes(self, axes, level, limit, tolerance, method, fill_value, /opt/conda/envs/python2/lib/python2.7/site-packages/pandas/core/frame.pyc in _reindex_axes(self, axes, level, limit, tolerance, method, fill_value, copy) 2677 if index is not None: 2678 frame = frame._reindex_index(index, method, copy, level, -> 2679 fill_value, limit, tolerance) 2680 2681 return frame /opt/conda/envs/python2/lib/python2.7/site-packages/pandas/core/frame.pyc in _reindex_index(self, new_index, method, copy, level, fill_value, limit, tolerance) 2685 new_index, indexer = self.index.reindex(new_index, method=method, 2686 level=level, limit=limit, -> 2687 tolerance=tolerance) 2688 return self._reindex_with_indexers({0: [new_index, indexer]}, 2689 copy=copy, fill_value=fill_value, /opt/conda/envs/python2/lib/python2.7/site-packages/pandas/core/indexes/base.pyc in reindex(self, target, method, level, limit, tolerance) 2865 target = self._simple_new(None, dtype=self.dtype, **attrs) 2866 else: -> 2867 target = _ensure_index(target) 2868 2869 if level is not None: /opt/conda/envs/python2/lib/python2.7/site-packages/pandas/core/indexes/base.pyc in _ensure_index(index_like, copy) 4025 index_like = copy(index_like) 4026 -> 4027 return Index(index_like) 4028 4029 /opt/conda/envs/python2/lib/python2.7/site-packages/pandas/core/indexes/base.pyc in __new__(cls, data, dtype, copy, name, fastpath, tupleize_cols, **kwargs) 324 **kwargs) 325 elif data is None or is_scalar(data): --> 326 cls._scalar_data_error(data) 327 else: 328 if (tupleize_cols and isinstance(data, list) and data and /opt/conda/envs/python2/lib/python2.7/site-packages/pandas/core/indexes/base.pyc in _scalar_data_error(cls, data) 676 raise TypeError('{0}(...) must be called with a collection of some ' 677 'kind, {1} was passed'.format(cls.__name__, --> 678 repr(data))) 679 680 @classmethod TypeError: Index(...) must be called with a collection of some kind, 'time' was passed 是一个arrP数组，在本例中是一个大小为3的数组，并且您已经指定了指向初始值为char *的c样式字符串的指针，它们本身是空终止的字符数组。所以，你的第一个答案是正确的。

Answer 2

要查找此类广告的答案，您可以使用cdecl。它很可能会回答你。

declare arrP1 as array of pointer to char

然而，有一种称为spiral rule的东西。它还可以帮助您阅读decleration。例如，

char *str[10]

         +-------+
         | +-+   |
         | ^ |   |
    char *str[10];
     ^   ^   |   |
     |   +---+   |
     +-----------+

-   str is an array of 10 elements
-   str is an array of 10, of pointers
-   str is an array of 10, of pointers, of type char

Answer 3

不确定这是否会有所帮助或使事情更加混乱，但arrP1既可以是char *也可以是char **，如下所示：

pip install iconv_codecs

有趣的事情（我刚刚发现自己）是foo2没有在其堆栈上创建数组的副本，它直接传递给arr！所有3个cout都打印相同的地址。

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