Why in the code “456”+1, output is “56” [duplicate]

by

The string literal "25" is really a char array of type const char[3] with values {'2', '5', '\0'} (the two characters you see and a null-terminator.) In C and C++, arrays can easily decay to pointers to their first element. This is what happens in this expression:

"25" + 1

where "25" decays to &"25"[0], or a pointer to the first character. Adding 1 to that gives you a pointer to 5.

On top of that, std::ostream, of which std::cout is an instance, prints a const char* (note that char* would also work) by assuming it is a null-terminated string. So in this case, it prints only 5.

More Related Contents:

  1. Insertion sort stops working after million input
  2. Why the values {1, 1, 0, -1, -1, -1, 0, 1} and {0, 1, 1, 1, 0, -1, -1, -1} were chosen for dx[dir] and dy[dir]? [closed]
  3. When to use volatile with multi threading?
  4. Accessing inactive union member and undefined behavior?
  5. How to add “-l” (ell) compiler flag in CMake
  6. AVX2 what is the most efficient way to pack left based on a mask?
  7. How to use Boost in Visual Studio 2010
  8. C++ Cross-Platform High-Resolution Timer
  9. Why is there an injected class name?
  10. Is it better to use std::memcpy() or std::copy() in terms to performance?
  11. What is the difference between atan and atan2 in C++?
  12. How to enable C++11 in Qt Creator?
  13. How to use std::sort to sort an array in C++
  14. Instantiate class from name?
  15. how to check whether two matrices are identical in OpenCV
  16. Why an unnamed namespace is a “superior” alternative to static? [duplicate]
  17. reading a line from ifstream into a string variable
  18. Are C++ Templates just Macros in disguise?
  19. Most efficient/elegant way to clip a number?
  20. How to print __int128 in g++?
  21. How to append a char to a std::string?
  22. What does flushing the buffer mean?
  23. no default constructor exists for class x (inheritance) C++
  24. Hash an arbitrary precision value (boost::multiprecision::cpp_int)
  25. Can Qt signals return a value?
  26. Adding signals/slots (QObject) to QGraphicsItem: performance hit?
  27. ReleaseSemaphore does not release the semaphore
  28. Why do some people prefer “T const&” over “const T&”?
  29. c++11 Thread class how to use a class member function
  30. Why is operator!= removed in C++20 for many standard library types?

Leave a Comment