std::ptrdiff_t

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C++
 
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ptrdiff_t
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Defined in header <cstddef>
typedef /*implementation-defined*/ ptrdiff_t;
std::ptrdiff_t两个指针相减的结果是有符号整数类型.
Original:
std::ptrdiff_t is the signed integer type of the result of subtracting two pointers.
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[编辑] 注释

std::ptrdiff_t用于指针的算术运算和数组下标，如果负值是可能的。使用其他类型，如int的程序，可能会失败，例如：当该指数超过64位系统INT_MAX，或者如果它依赖于32位模数.
Original:
std::ptrdiff_t is used for pointer arithmetic and array indexing, if negative values are possible. Programs that use other types, such as int, may fail on, e.g. 64-bit systems when the index exceeds INT_MAX or if it relies on 32-bit modular arithmetic.
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当使用C + +容器库的正确类型，迭代器之间的差异是的成员typedefdifference_type，这是经常的代名词std::ptrdiff_t.
Original:
When working with the C++ container library, the proper type for the difference between iterators is the member typedef difference_type, which is often synonymous with std::ptrdiff_t.
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只有相同的数组元素（包括过去数组结尾的指针1）的指针，也可以彼此相减.
Original:
Only pointers to elements of the same array (including the pointer one past the end of the array) may be subtracted from each other.
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如果数组是如此之大（大于PTRDIFF_MAX元素，但小于SIZE_MAX字节），两个指针之间的差可能并不表示为std::ptrdiff_t减去两个这样的指针，结果是未定义.
Original:
If an array is so large (greater than PTRDIFF_MAX elements, but less than SIZE_MAX bytes), that the difference between two pointers may not be representable as std::ptrdiff_t, the result of subtracting two such pointers is undefined.
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对于字符数组短比PTRDIFF_MAX，std::ptrdiff_t的签名对应的std::size_t作为：它可以存储任何类型的数组的大小，并是在大多数平台上，代名词std::intptr_t）.
Original:
For char arrays shorter than PTRDIFF_MAX, std::ptrdiff_t acts as the signed counterpart of std::size_t: it can store the size of the array of any type and is, on most platforms, synonymous with std::intptr_t).
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[编辑] 为例

#include <cstddef>
int main()
{
    const std::size_t N = 100;
    int* a = new int[N];
    int* end = a + N;
    for(std::ptrdiff_t i = N; i>0; --i)
        *(end - i) = i;
    delete[] a;
 
}


[编辑] 另请参阅
返回无符号整数类型的sizeof运营商
Original:
unsigned integer type returned by the sizeof operator
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（的typedef） [edit]
一个标准的布局类型指定的成员从一开始的字节偏移量
Original:
byte offset from the beginning of a standard-layout type to specified member
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（函数宏） [edit]
来自“http://zh.cppreference.com/mwiki/index.php?title=cpp/types/ptrdiff_t&oldid=26825”