Thread: overloading operator errors

I am using GMP to process huge numbers. I need to overload +,-,/ and * operators to handle operations between double, mpz_t (gmp type) and char*. When I try to declare the operator, I have errors:

declararion: mpf_t& operator+(mpf_t& v1, double v2);

error:

functions.cpp:10: error: `__mpf_struct (& operator+(__mpf_struct (&)[1], double)
)[1]' must have an argument of class or enumerated type

Thanks any help!

You can only overload operator for which at least one of the arguments is a CLASS or reference to it. You're trying to overload a operator that receives a double and a pointer..

Code:

class A{};
A* operator+(const A* a,char){}
int main(){
	A a;
	&a+'h';
	return 0;
}

and the error

Code:

$ make
g++ -Wall -c ./main.cpp -o obj/./main.o
./main.cpp:24: error: `A* operator+(const A*, char)' must have an argument of cl
ass or enumerated type
./main.cpp: In function `int main()':
./main.cpp:27: warning: statement has no effect
./main.cpp:29:2: warning: no newline at end of file
make: *** [obj/./main.o] Error 1

In case you didn't know.....GMP has a C++ class interface.

gg

Yes, it seems that the compiler does not recognize mpf_t as a struct, very strange indeed. Codeplug, I know that GMP has a C++ interface. The problem is that I was trying to use GMP in Windows. I have not found a compiled version of GMP that supports the C++ interface, and I was unable to compile full GMP under Cygwin. I'll move to Linux, the Windows was a restriction from the project.

Thanks for the replyies anyway. I am already compiling GMP under Linux to use its C++ interface.

Uhm... I forgot my real problem, sorry! The most important overload would be:

Code:

mpf_t operator+(char*, double);

What is impossible. The problem is that I have huge constants exported from a mathematical software into C code. Also, the code has operations with double, like pow. I can't represent the constants like any type, except char*.

I have made a parser that translate these huge constants into strings (not the std::string). The only solution I can think of, it is to overload the plus operator to std::string and double. Then I change my parser to produce the following output:

3987543756234

to

std::string("3987543756234 ")

Is this a good solution? Thanks any reply.