Problem with the pow( ) function [modified]

[KaKa]

Hi, I am using Visual C++ 2005 to write code a win32 console application. There was an error message about the power function when I compiled the code. It is: error c2668: 'pow' :ambiguous call to overloaded function. The statement is: tempDistance += pow((data[selectedInstance][k]-data[j][k]),2); I used various headers like: cmath and math.h but the error message remained the same. What is the cause of the error? I've checked the syntax and it seems correct. -- modified at 13:30 Wednesday 19th July, 2006

[David Crow]

KaKa` wrote:

There was an error message about the power function when I compiled the code. It is: error c2668: 'pow' :ambiguous call to overloaded function.

Apparently there's more than one pow() function. Which one do you want to use?

---

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[toxcct]

how is defined the data matrix (what type) ? i think it contains values other than int, that's why the compiler doesn't know which function to call (pow(int, int) or pow(double, double) ?? ).

---

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[pgav]

I'm thinking that it could have something to do with your data types... are all your variables "int", or are you mixing types? Patrick

[cppcook]

If you couldn't figure out the problem, why don't you write your own pow() function? It's simple...

[Zac Howland]

cppcook wrote:

If you couldn't figure out the problem, why don't you write your own pow() function? It's simple...

Simple for integer exponents ... not so simple for decimal exponents. As for the original post, my guess is that you are mixing types (that is, raising a double by an integer power). While there is nothing wrong with that, pow is usually defined: From MSDN:

double pow(
   double x,
   double y 
);
double pow(
   double x,
   int y
);  // C++ only
double pow(
   int x,
   int y
);  // C++ only
float pow(
   float x,
   float y 
);  // C++ only
float pow(
   float x,
   int y
);  // C++ only
long double pow(
   long double x,
   long double y
);  // C++ only
long double pow(
   long double x,
   int y
);  // C++ only
float powf(
   float x,
   float y 
);

Try explicitly casting your types:

double base = 3.0;
int power = 5;
int result = pow(base, (double)power);

If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week Zac

[Ennis Ray Lynch Jr]

Is a result of implicit casts being available. Explicitly case each parameter to the datatype to use that matches one of the pow formal parameter lists. A man said to the universe: "Sir I exist!" "However," replied the Universe, "The fact has not created in me A sense of obligation." -- Stephen Crane

[NrmMyth]

If you know nothing about function overloading just cast both parameters to (double) and it will compile. tempDistance += pow(((double)data[selectedInstance][k]-data[j][k]),2.0);

[KaKa]

Thanks all for the replies.......i used the simple way and cast both parameters to double and it can work now.