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I defined a linked list in C++. I am trying to set a NULL value to the variable head (in the constructor of Movie_LinkedList), but I got:
movie.h(40): error C2065: 'NULL' : undeclared identifier
please note that I can't include any library except of iostream
Any help appreciated!
409
NULL is not a built-in constant in the C or C++ languages.
NULL is defined in the following header files: CRTDBG. H, LOCALE. H, STDDEF. H, STDIO.
The identifier is undeclaredIf the identifier is a variable or a function name, you must declare it before it can be used. A function declaration must also include the types of its parameters before the function can be used.
As written, NULL isn't defined in your program. Usually, that's defined in a standard header file -- specifically <cstddef> or <stddef.h>. Since you're restricted to iostream, if yours doesn't get NULL implicitly from that header, you can use 0 or, in C++11, nullptr, which is a keyword and doesn't require a header. (It is not recommended to define NULL yourself. It might work sometimes, but it is technically illegal.)
72
You should include <stddef.h> or <cstddef>.
However you can use 0 or nullptr too.
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