How can I use a custom type as key for a map in C++?

by

I suspect you need

bool operator<(const Foo& foo1) const;

Note the const after the arguments, this is to make “your” (the left-hand side in the comparison) object constant.

The reason only a single operator is needed is that it is enough to implement the required ordering. To answer the abstract question “does a have to come before b?” it is enough to know whether a is less than b.

More Related Contents:

  1. What is difference between const and non const key?
  2. Call an array from within an array of structs in c++
  3. i dont know this use of struct and pointers
  4. What are the basic rules and idioms for operator overloading?
  5. Operator[][] overload
  6. C/C++ Struct vs Class
  7. What are the differences between struct and class in C++?
  8. Struct padding in C++
  9. Using char* as a key in std::map
  10. Iterating over a struct in C++
  11. Iterate through Struct and Class Members [duplicate]
  12. Is the memory allocated for struct members continguous? What if a struct member is an array?
  13. overloading new/delete
  14. What is the preferred/idiomatic way to insert into a map?
  15. What is the default value for C++ class members
  16. Is it legal to index into a struct?
  17. How to overload the operator++ in two different ways for postfix a++ and prefix ++a?
  18. std::map default value
  19. Rationale of enforcing some operators to be members
  20. Is the size of a struct required to be an exact multiple of the alignment of that struct?
  21. return value of operator overloading in C++
  22. How to overload unary minus operator in C++?
  23. std::map default value for build-in type
  24. Thread safety of std::map for read-only operations
  25. C++ Structure Initialization [duplicate]
  26. too many initializers for ‘int [0]’ c++
  27. C++ why the assignment operator should return a const ref in order to avoid (a=b)=c
  28. Why default three-way operator (spaceship ) generates equality operator (==) and user define three-way operator not?
  29. Why we need to return reference to istream/ostream while overloading >> and
  30. using declaration in variadic template

Leave a Comment