transform algorithm and casting of functions

[suresh]

Hi

I saw this code in the net for converting case.

string s = "Amma";
transform(s.begin(),s.end(),s.begin(),(int(*)(int) )toupper);

Q: what is the meaning of (int(*)(int))toupper ?

The code works fine when (int(*)(int))toupper is replaced
by ::toupper. But the code does not even compile, when i write just
std::toupper i.e.
transform(s.begin(),s.end(),s.begin(),std::toupper ); //not even
compiling

Could you please explain the difference between the three?

thanks
suresh

[Abhishek Padmanabh]

On Dec 22, 8:08*pm, suresh <[e-mail]:

Hi

I saw this code in the net for converting case.

string s = "Amma";
transform(s.begin(),s.end(),s.begin(),(int(*)(int) )toupper);

Q: what is the meaning of *(int(*)(int))toupper ?

It means it is casting pointer to function toupper as a pointer to a
function having return type as int and takes one int argument. I think
that is not required as toupper is of the same function pointer type.

The code works fine when (int(*)(int))toupper is replaced
by ::toupper. But the code does not even compile, when i write just
std::toupper i.e.
transform(s.begin(),s.end(),s.begin(),std::toupper ); //not even
compiling

Could you please explain the difference between the three?

I think you are using VC++ 6.0 (or something as old/non-conforming as
that). It does not put the C APIs into std namespace (they are in
global namespace). Get rid of it and std::toupper works.

[suresh]

Thanks abhishek for the comments. But I am using g++ on a debian etch
machine. It is not VC++ and std::toupper is not compiling...

any suggestions?

suresh

On Dec 22, 10:34 pm, Abhishek Padmanabh <[e-mail]>
wrote:

On Dec 22, 8:08 pm,suresh<[e-mail]:

Hi

I saw this code in the net for converting case.

string s = "Amma";
transform(s.begin(),s.end(),s.begin(),(int(*)(int) )toupper);

Q: what is the meaning of (int(*)(int))toupper ?

It means it is casting pointer to function toupper as a pointer to a
function having return type as int and takes one int argument. I think
that is not required as toupper is of the same function pointer type.

The code works fine when (int(*)(int))toupper is replaced
by ::toupper. But the code does not even compile, when i write just
std::toupper i.e.
transform(s.begin(),s.end(),s.begin(),std::toupper ); //not even
compiling

Could you please explain the difference between the three?

I think you are using VC++ 6.0 (or something as old/non-conforming as
that). It does not put the C APIs into std namespace (they are in
global namespace). Get rid of it and std::toupper works.