Member Login

Remember Me
Forgot Password?
Join Us!

Come Join Us!

Are you a
Computer / IT professional?
Join Tek-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

Join Tek-Tips
*Tek-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.
Jobs from Indeed

Link To This Forum!

Partner Button
Add Stickiness To Your Site By Linking To This Professionally Managed Technical Forum.
Just copy and paste the
code below into your site.

C++ STL Map

C++ STL Map


I am getting a strange build error message when creating a simple STL map.

"stl_function.h passing `const CWord508' as `this' argument of `bool CWord508::operator<(CWord508)' discards qualifiers"

The error is triggered on the map.insert(<key object, other object> line

I have provided a operator < function on the key object class:

class CWord508 {
      char str[20];
       CWord508( char *s );
       char *get();
// must define operator "less than" for CWord508 objects
       bool operator<( CWord508 a);
       bool operator==( CWord508 a);

the c++ code is in separate file:
bool CWord508::operator<( CWord508 a)
     return (strcmp( str, a.get() ) < 0 );

I cannot see an obvious flaw with the code; any help / suggestions welcome.
NB I have tried providing operator> as well just in case.



RE: C++ STL Map

Change definitions to


       bool operator<( const CWord508& a) const;
       bool operator==( const CWord508& a) const;

RE: C++ STL Map

Thanks, that was a helpful reply,

I tried that adjustment and get the same error msg, reported, albeit in a different place:

'In member function bool CWord508::operator<(const CWord508&)'
passing const CWord508' as `this' argument of `char* CWord508::get()' discards qualifiers"

bool CWord508::operator<( const CWord508& a) const
   return ( str < a.get() );  // error reported here
char *CWord508::get()  const
   return str;

I remain baffled as to how to work round this build error

Thanks for any suggestions

RE: C++ STL Map

Hmm, it's a very very dangerous class...


class CWord508
  CWord508(const char *s);
  char *get() { return str; } // why "get"?
  const char* get() const { return str; }
  // must define operator "less than" for CWord508 objects
  bool operator <(const CWord508& a) const {
       return strcmp(str,a.str) < 0; // (or a.get() ;)
  bool operator==(const CWord508& a) const {
       return strcmp(str,a.str) == 0;
  char str[20];

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Tek-Tips Forums free from inappropriate posts.
The Tek-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Tek-Tips forums is a member-only feature.

Click Here to join Tek-Tips and talk with other members!


Close Box

Join Tek-Tips® Today!

Join your peers on the Internet's largest technical computer professional community.
It's easy to join and it's free.

Here's Why Members Love Tek-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close