set head to NULL (‘NULL’ : undeclared identifier)

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.)

Related Posts:

  1. C++ – Assigning null to a std::string
  2. What are the differences between a pointer variable and a reference variable in C++?
  3. Return array in a function
  4. What does “dereferencing” a pointer mean?
  5. Regular cast vs. static_cast vs. dynamic_cast
  6. What is a smart pointer and when should I use one?
  7. What does “dereferencing” a pointer mean?
  8. What is a char*?
  9. Using NULL in C++?
  10. What exactly is nullptr?
  11. How to fix a “invalid operands to binary expression” error?
  12. What is a dangling pointer?
  13. What does `*&` in a function declaration mean?
  14. (->) arrow operator and (.) dot operator , class pointer
  15. What is uintptr_t data type
  16. What is the difference between const int*, const int * const, and int const *?
  17. C++ – No matching member function for call to ‘push_back’
  18. What is uintptr_t data type
  19. What does int & mean
  20. What is the difference between const int*, const int * const, and int const *?
  21. Pointer to incomplete class type is not allowed
  22. Passing a 2D array to a C++ function
  23. basic_string::_M_construct null not valid after constructing subvector of strings
  24. Can’t resolve Error: indirection requires pointer operand (‘int’ invalid)
  25. How to create a dynamically-allocated array of const objects, but have values assigned to them?
  26. How to access the contents of a vector from a pointer to the vector in C++?
  27. How to make an array with a dynamic size? General usage of dynamic arrays (maybe pointers too)?
  28. What does int & mean
  29. C++: Expression must have a constant value when declaring array inside function
  30. Sorting Linked List C++ with pointers
  31. Delete 2D array C++
  32. Is the sizeof(some pointer) always equal to four?
  33. C++ Expression must have pointer-to-object type
  34. C++ strings and pointers
  35. initial value of reference to non-const must be an lvalue
  36. Typedef function pointer?
  37. How to initialize a vector of pointers
  38. What is the use of intptr_t?
  39. Check if C++ Array is Null
  40. error: invalid initialization of non-const reference of type ‘int&’ from an rvalue of type ‘int’
  41. Using C-string gives Warning: “Address of stack memory associated with local variable returned”
  42. Reference to non-static member function must be called
  43. Why use pointers?
  44. What’s the difference between * and & in C?
  45. C++ pass an array by reference
  46. Function stoi not declared
  47. C++ Array of pointers: delete or delete []?
  48. Why should I use a pointer rather than the object itself?
  49. Function stoi not declared
  50. C++ correct way to return pointer to array from function
  51. Warning: comparison of distinct pointer types
  52. Is null reference possible?
  53. Initializing pointers in C++
  54. Difference between function arguments declared with & and * in C++
  55. Is C++ Array passed by reference or by pointer?
  56. Difference between the int * i and int** i
  57. What is a `char*`?
  58. clearing a vector of pointers [duplicate]
  59. C++ Swapping Pointers
  60. Array of Linked Lists C++
  61. Is it still safe to delete nullptr in c++0x?
  62. Differences between unique_ptr and shared_ptr
  63. Sleep for milliseconds
  64. C++ Cout & Cin & System “Ambiguous” [closed]
  65. undefined reference to `WinMain@16′
  66. How can I clear console
  67. How to go from fopen to fopen_s
  68. invalid new-expression of abstract class type error
  69. How can I create objects while adding them into a vector?
  70. what does “error : a nonstatic member reference must be relative to a specific object” mean?
  71. “Symbol(s) not found for architecture x86_64” on QtCreator project
  72. What does the assignment of ~0u to a variable mean in C++?
  73. expected expression in C++?
  74. printf with std::string?
  75. What’s the most efficient way to erase duplicates and sort a vector?
  76. How can I iterate through a string and also know the index (current position)?
  77. c++ parse int from string [duplicate]
  78. C++ array assign error: invalid array assignment
  79. Is there a median function in the C++ library?
  80. What is object slicing?
  81. Java equivalent of cin (C++)
  82. g++ “because the following virtual functions are pure” with abstract base class
  83. why can’t I dereference an iterator?
  84. expected identifier before string constant
  85. C++ error: expected identifier before “(” token
  86. Function for C++ struct
  87. C++ error: double free or corruption (fasttop)
  88. no match for ‘operator<<’ in ‘std::operator
  89. error: switch quantity not an integer
  90. How to create a vector of class objects in C++?
  91. Is clrscr(); a function in C++?
  92. Cross compiler prefix and path in eclipse
  93. How to write log base(2) in c/c++
  94. Reading a string from file c++
  95. Expected unqualified-id before ‘[‘ token
  96. C++ Error: Invalid conversion from ‘char’ to ‘const char*’
  97. Evaluate a string with a switch in C++ [duplicate]
  98. C++ JSON Serialization
  99. stack around the variable…was corrupted
  100. Creating a list to hold objects in C++

Leave a Comment