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Is size_type and size_t the same?| unregistered (86) |  |
| as above? | |
| jsmith (3772) | |
| Not necessarily. I assume by size_type you mean the typedef inside most STL containers? If so, then just because size_type was added to all the containers instead of just using size_t means that the STL is reserving the right to make size_type any type they like. (By default, in all implementations I'm aware of size_type is a typedef of size_t). | |
| unregistered (86) | |
| 1) in which libraries is size_t defined or present in? because I discovered that including either cstdlib or iostream would define size_t. 2) what datatype exactly is size_t typedef to? 3) in which libraries is size_type defined or present in? 4) since size_type is almost always typedef to size_t, I guess most of the time it would be of size_t type, am I right? 5) When and where are size_t and size_type used? because when I compare the result of an int and the result of member function length() of string class, it gives me a warning comparison of signed and unsigned types. Thanks for the help | |
| firedraco (2585) | |
| 1.) Probably most things that use a size_type variable (since they typedef it to size_t like jsmith said, they need to include whatever has it) 2.) Idr, it's probably an unsigned int or an unsigned long int.3.) AFAIK, all of the STL containers/stuff that would have a size() member function. 4.) Yes, most of the time. 4.) The warning it because size_t/size_type are unsigned types. They are used when you call the size() member function (and possibly other functions that return size-like variables) | |
| unregistered (86) | |
| according to here: http://www.cppreference.com/wiki/string/size the size member function returns a size_type but when I try to delcare a size_type variable as in size_type a; in my program after including the string library I get this error: error: ‘size_type’ was not declared in this scope why is this happening and how do I resolve this problem? btw, where can I find all the typedefs and function prototypes of each library? I'm using linux... | |
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| jsmith (3772) | |
| size_type is always a typedef inside the class. For example, std::vector<int> v; std::vector<int>::size_type sz = v.size(); std::string s; std::string::size_type sz = s.size(); (I'm going to guess that size_t is unsigned int because I know on my 32-bit platform it is 32 bits. Meaning on a 64-bit platform it is likely 64 bits.) | |
| unregistered (86) | |
| so to play safe, I should use size_type whenever size_type is specified as a parameter/return value as on the cpp reference and size_t when specified as such right? so that whenever the implementation changes I wouldn't have to change my program unlike when I used int in the past in place of size_t and size_type | |
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| firedraco (2585) | |
| Yes, if you want to be 100% sure it will always work, then use size_type when you can. | |
| unregistered (86) | | |
what about size_t? should I use size_type in place of it too? I guess not right? and thanks to everyone who has helped | ||
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| jsmith (3772) | |
| use size_t to hold size_ts and size_type to hold size_types. | |
| JivanAmara (37) | | |
You can usually find them in the headers in /usr/include/c++/<version>/It can be a little overwhelming at first, but I think poking through the headers helps you to learn. Remember that every compiler doesn't have to do it the same way though. | ||
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