- Where does
size_tcome from when I don't have anything included? - Is it reasonable to always assume
size_t==std::size_t? - When should I use the
size_typeinstdcontainers (string::size_type,vector<T>::size_type, etc)?
当我没有包含任何东西时,size_t来自哪里?
总是假设size_t == std :: size_t是否合理?
我什么时候应该在std容器中使用size_type(string :: size_type,vector
3 个解决方案
#1
10
Where does size_t come from when I don't have anything included in an empty project?
当我没有包含在空项目中的任何内容时,size_t来自哪里?
If you don't have anything included, then you can't use size_t. It's defined in <stddef.h> (and perhaps also in <cstddef>, if your version of that header puts the definitions in the global namespace as well as std).
如果您没有包含任何内容,则不能使用size_t。它在
Is it reasonable to always assume size_t == std::size_t?
总是假设size_t == std :: size_t是否合理?
Yes. All types and functions defined by the C library are included in the std namespace, as long as you include the appropriate C++ header (e.g. <cstddef> rather than <stddef.h>)
是。只要包含适当的C ++头(例如
When should I use std::_::size_type?
我什么时候应该使用std :: _ :: size_type?
Do you mean the size_type types defined in some standard classes and templates such as vector? You could use those when using those classes if you like. In most cases, you'll know that it's the same as size_t, so you might as well use that and save a bit of typing. If you're writing generic code, where you don't know what the class is, then it's better to use size_type in case it's not compatible with size_t.
你的意思是在一些标准类和模板中定义的size_type类型,例如vector?如果您愿意,可以在使用这些类时使用它们。在大多数情况下,你会知道它与size_t相同,所以你不妨使用它并节省一些输入。如果您正在编写通用代码,而您不知道该类是什么,那么最好使用size_type,以防它与size_t不兼容。
For example, you might want to write a container designed to hold more items than can be represented by size_t. You might use some kind of big number type to represent the container's size, which isn't convertible to size_t. In that case, code like size_t s = c.size() would fail to compile - you'd need to use Container::size_type instead.
例如,您可能希望编写一个容器,用于容纳比size_t表示的更多的项目。您可以使用某种大数字类型来表示容器的大小,该大小不可转换为size_t。在这种情况下,像size_t s = c.size()这样的代码将无法编译 - 您需要使用Container :: size_type。
#2
1
Where does size_t come from when I don't have anything included in an empty project?
当我没有包含在空项目中的任何内容时,size_t来自哪里?
size_t is a base unsigned integer memsize-type defined in the standard library of C/C++ languages. It is defined in "stddef.h" for C and in <cstddef> for C++.
size_t是在C / C ++语言的标准库中定义的基本无符号整数memsize-type。它在C的“stddef.h”中定义,在C ++的
Types defined by the header file "stddef.h" are located in the global namespace while <cstddef> header places the size_t type in the namespace std.
头文件“stddef.h”定义的类型位于全局名称空间中,而
"stddef.h" from C is included into C++ for compatibility, and hence the type can be found in both the global namespace (::size_t) and the std namespace (std::size_t).
来自C的“stddef.h”包含在C ++中以实现兼容性,因此可以在全局命名空间(:: size_t)和std命名空间(std :: size_t)中找到该类型。
#3
0
size_t is defined in <cstddef> and is in std namespace.
size_t在
#1
10
Where does size_t come from when I don't have anything included in an empty project?
当我没有包含在空项目中的任何内容时,size_t来自哪里?
If you don't have anything included, then you can't use size_t. It's defined in <stddef.h> (and perhaps also in <cstddef>, if your version of that header puts the definitions in the global namespace as well as std).
如果您没有包含任何内容,则不能使用size_t。它在
Is it reasonable to always assume size_t == std::size_t?
总是假设size_t == std :: size_t是否合理?
Yes. All types and functions defined by the C library are included in the std namespace, as long as you include the appropriate C++ header (e.g. <cstddef> rather than <stddef.h>)
是。只要包含适当的C ++头(例如
When should I use std::_::size_type?
我什么时候应该使用std :: _ :: size_type?
Do you mean the size_type types defined in some standard classes and templates such as vector? You could use those when using those classes if you like. In most cases, you'll know that it's the same as size_t, so you might as well use that and save a bit of typing. If you're writing generic code, where you don't know what the class is, then it's better to use size_type in case it's not compatible with size_t.
你的意思是在一些标准类和模板中定义的size_type类型,例如vector?如果您愿意,可以在使用这些类时使用它们。在大多数情况下,你会知道它与size_t相同,所以你不妨使用它并节省一些输入。如果您正在编写通用代码,而您不知道该类是什么,那么最好使用size_type,以防它与size_t不兼容。
For example, you might want to write a container designed to hold more items than can be represented by size_t. You might use some kind of big number type to represent the container's size, which isn't convertible to size_t. In that case, code like size_t s = c.size() would fail to compile - you'd need to use Container::size_type instead.
例如,您可能希望编写一个容器,用于容纳比size_t表示的更多的项目。您可以使用某种大数字类型来表示容器的大小,该大小不可转换为size_t。在这种情况下,像size_t s = c.size()这样的代码将无法编译 - 您需要使用Container :: size_type。
#2
1
Where does size_t come from when I don't have anything included in an empty project?
当我没有包含在空项目中的任何内容时,size_t来自哪里?
size_t is a base unsigned integer memsize-type defined in the standard library of C/C++ languages. It is defined in "stddef.h" for C and in <cstddef> for C++.
size_t是在C / C ++语言的标准库中定义的基本无符号整数memsize-type。它在C的“stddef.h”中定义,在C ++的
Types defined by the header file "stddef.h" are located in the global namespace while <cstddef> header places the size_t type in the namespace std.
头文件“stddef.h”定义的类型位于全局名称空间中,而
"stddef.h" from C is included into C++ for compatibility, and hence the type can be found in both the global namespace (::size_t) and the std namespace (std::size_t).
来自C的“stddef.h”包含在C ++中以实现兼容性,因此可以在全局命名空间(:: size_t)和std命名空间(std :: size_t)中找到该类型。
#3
0
size_t is defined in <cstddef> and is in std namespace.
size_t在