Programming Forums > Application Development > C++

Kazy · Apr 13th, 2006, 3:30 PM

I'm looking for the best way to represent a math function like:
f(x) = x^(9/2) in programming. I've tried to look this up by google, but I don't know what to search for because the term "function" it way to broad when dealing with programming. Is there some kind of class for this? Thanks!

a3orange · Apr 13th, 2006, 4:09 PM

What math function are you using for f(x)?

hbe02 · Apr 13th, 2006, 4:10 PM

arent you looking for something as simple as this:

(Toggle Plain Text)

#include<iostream.h>
#include<cmath>


double function(double x)
{
	 
    return pow(x,4.5);
     
         
 }

int main()
{
	cout<<function(3)<<endl;
	return 0;
}

a3orange · Apr 13th, 2006, 4:11 PM

Ooh, that's what you wanted. (I wasn't sure if you wanted multiplication for the first one)

grumpy · Apr 13th, 2006, 7:16 PM

In C++, heb02's example should actually be;

(Toggle Plain Text)

#include<iostream>
#include<cmath>

double function(double x)
{
   return std::pow(x,4.5);
}

int main()
{
	std::cout<<function(3.0)<<endl;
	return 0;
}

Of course, that assumes by ^ Kazy means "to the power of" and (s)he think of his terms are real numbers.

If we just gave the compiler x^(9/2), the compiler would turn that into x^4 (as 9 and 2 are integers, so 9/2 is 4), and that would cause a compile error unless x is an integral type. If x is an integral type, some bits of x would be fiddled.

If you want to find information on the C++ standard, google for "C++ standard library" or "C standard library" (as C++ also allows use of the C standard library, but deprecates it). Both include functions for doing floating point mathematics.

biohazard · Apr 14th, 2006, 3:03 AM

Grumpy, shouldnt we use namespace std?

grumpy · Apr 14th, 2006, 3:33 AM

Quote:

Originally Posted by biohazard

Grumpy, shouldnt we use namespace std?

Look that the code I gave again. It is explicitly using functions in namespace std. There is no requirement for a "using namespace std;" directive.

InfoGeek · Apr 14th, 2006, 3:19 AM

biohazard, I think you mean shouldn't we simply put

(Toggle Plain Text)

using namespace std;

at the top after including the files.

Yes, we can do it. If we do, we don't need to specify the std:: prefix everytime we use something from the std namespace. But it's not recommended to do this in a header file. Also I'd bring the whole of the std namespace into scope. If you just want a few of the elements, you can specify them individually like:

(Toggle Plain Text)

using std::cout;
using std::cin;
using std::endl;

tempest · Apr 14th, 2006, 3:38 AM

Completely unrelated, I just noticed Grumpy was user #2600.

Jimbo · Apr 14th, 2006, 5:07 AM

I'm slightly curious as to whether the OP may have been looking for something like syntax trees instead of a hard-coded function...

Apr 13th, 2006, 3:30 PM	#1
Kazy Newbie Join Date: Sep 2005 Posts: 21 Rep Power: 0	Math functions in programming I'm looking for the best way to represent a math function like: f(x) = x^(9/2) in programming. I've tried to look this up by google, but I don't know what to search for because the term "function" it way to broad when dealing with programming. Is there some kind of class for this? Thanks!

Apr 13th, 2006, 4:10 PM	#3
hbe02 Hobbyist Programmer Join Date: Mar 2006 Location: Lebanon Posts: 148 Rep Power: 3	arent you looking for something as simple as this: (Toggle Plain Text) #include<iostream.h> #include<cmath> double function(double x) { return pow(x,4.5); } int main() { cout<<function(3)<<endl; return 0; } #include<iostream.h> #include<cmath> double function(double x) { return pow(x,4.5); } int main() { cout<<function(3)<<endl; return 0; }

Apr 13th, 2006, 7:16 PM	#5
grumpy Programming Guru Join Date: Jun 2005 Location: Adelaide, South Australia Posts: 1,260 Rep Power: 5	In C++, heb02's example should actually be; (Toggle Plain Text) #include<iostream> #include<cmath> double function(double x) { return std::pow(x,4.5); } int main() { std::cout<<function(3.0)<<endl; return 0; } #include<iostream> #include<cmath> double function(double x) { return std::pow(x,4.5); } int main() { std::cout<<function(3.0)<<endl; return 0; } Of course, that assumes by ^ Kazy means "to the power of" and (s)he think of his terms are real numbers. If we just gave the compiler x^(9/2), the compiler would turn that into x^4 (as 9 and 2 are integers, so 9/2 is 4), and that would cause a compile error unless x is an integral type. If x is an integral type, some bits of x would be fiddled. If you want to find information on the C++ standard, google for "C++ standard library" or "C standard library" (as C++ also allows use of the C standard library, but deprecates it). Both include functions for doing floating point mathematics.

Apr 14th, 2006, 3:19 AM	#8
InfoGeek Professional Programmer Join Date: Jun 2005 Location: India, The great. Posts: 435 Rep Power: 4	biohazard, I think you mean shouldn't we simply put (Toggle Plain Text) using namespace std; using namespace std; at the top after including the files. Yes, we can do it. If we do, we don't need to specify the std:: prefix everytime we use something from the std namespace. But it's not recommended to do this in a header file. Also I'd bring the whole of the std namespace into scope. If you just want a few of the elements, you can specify them individually like: (Toggle Plain Text) using std::cout; using std::cin; using std::endl; using std::cout; using std::cin; using std::endl; __________________ PFO - My daily dose of technology.

Apr 14th, 2006, 3:38 AM	#9
tempest Programming Guru Join Date: Oct 2004 Posts: 1,041 Rep Power: 6	Completely unrelated, I just noticed Grumpy was user #2600. __________________

Apr 13th, 2006, 4:09 PM	#2
a3orange Newbie Join Date: Apr 2006 Posts: 14 Rep Power: 0	What math function are you using for f(x)?

Apr 13th, 2006, 4:11 PM	#4
a3orange Newbie Join Date: Apr 2006 Posts: 14 Rep Power: 0	Ooh, that's what you wanted. (I wasn't sure if you wanted multiplication for the first one)

Apr 14th, 2006, 3:03 AM	#6
biohazard Newbie Join Date: Feb 2006 Posts: 18 Rep Power: 0	Grumpy, shouldnt we use namespace std?

Apr 14th, 2006, 5:07 AM	#10
Jimbo Battle Programmer Join Date: Feb 2006 Location: Bellevue, WA, USA Posts: 770 Rep Power: 3	I'm slightly curious as to whether the OP may have been looking for something like syntax trees instead of a hard-coded function...

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Programming Forums > Application Development > C++

Math functions in programming