Using imaginary number " i ". Dev C++ vs. VS2008!

Hi There!

I created an algorithm that uses imaginary numbers. It is fine on Dev C++, and now I am trying to port to VS2008. I figured out most things, including how to declare complex numbers. However, I've been having an incredible hard time trying to figure how to use the " i " number! For example:

In Dev C++:

Code:

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z_cmplx = cexp(I * f1/Fs * 2 * PI);

---

Where "I" is a macro from the library!

In VS2008:

Code:

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z_cmplx = std::exp(I * f1/Fs * 2 * PI);

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Although I DID include <complex> library just like I did before, the compiler gives me: error C2065: 'I' : undeclared identifier.

This is a pretty time sensitive matter, if anyone could help I'd REALLY appreciate! :wave:

Thank you in advance.

Best wishes,

Fernando

I'm not an expert on using the complex class, but I believe that for complex numbers, exp works on a complex variable where a complex variable is defined to have a real and imaginary part.

So assuming fl/Fs and PI are real then you would define a complex number

Code:

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complex<double> com1(0, fl/Fs * 2 * PI);  //This gives an imaginary number ie 0 + i*fl/Fs * 2 * PI

complex<double> com2 = exp(com1);

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Quote:

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Originally Posted by fernando306

Where "I" is a macro from the library!

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You have to be joking.

Do you know the number of naming conflicts a 1 letter name would have in a large program? Or how about searching your source files for the usage of the I macro?

Macro names should be named in a descriptive manner, so that conflicts and confusion doesn't occur.

Regards,

Paul McKenzie

Well the problem comes from an even more basic level...

I am not finding a way to set values to real and imaginary parts of the number separately.

I found that the function real(complex_number) returns the real part of the number, and so does the function imag(complex_number) returns the imaginary part. However I can't set them.

In Dev C++ I do that by using:

__real__ complex_number = desired_real_value
and
__imag__ complex_number = desired_imag_value

However in VC++ 2008 I've been trying for hours to find a way and I still havent found! MSDN documentation only shows how to RETURN the values, not to set them. Been having a hard time here... Anyone knows it??

Thanks.

I found no problem setting the values when declaring the complex numbers btw. But after has been declared, I didn't find a way to change the imaginary part of it. In therms of computational efficiency I don't think that it's a good idea do declare it all the time to be able to set values...

Quote:

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Originally Posted by fernando306

I found no problem setting the values when declaring the complex numbers btw. But after has been declared, I didn't find a way to change the imaginary part of it. In therms of computational efficiency I don't think that it's a good idea do declare it all the time to be able to set values...

---

Do you mean setting real and imaginary parts separately like this?

Code:

---

#include <iostream>
#include <complex>
using namespace std;

int main()
{
const double fl = 2, Fs = 3;
const double PI = 3.1416;

typedef complex<double> Compnum;

Compnum com1(0, fl/Fs * 2 * PI);  //This gives an imaginary number ie 0 + i*fl/Fs * 2 * PI

Compnum com2 = exp(com1);

Compnum com3 (3, 4);

        cout << com3 << endl << com2 << endl;

        com3 = Compnum(real(com3), 6);
        com2 = Compnum(2, imag(com2));

        cout << com3 << endl << com2 << endl;
        return 0;
}

---

This produces the output

Code:

---

(3,4)
(-0.499992,-0.86603)
(3,6)
(2,-0.86603)

---

where the imaginary part of com3 has been set directly keeping the real part and the real part of com2 has been set directly keeping the imaginary part.

>> Where "I" is a macro from the library!
"I" is part of C99, which VC2008 does not support.

Perhaps you could create a global complex<double> I.

gg

Quote:

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Originally Posted by Codeplug

>> Where "I" is a macro from the library!
"I" is part of C99, which VC2008 does not support.

Perhaps you could create a global complex<double> I.

gg

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I hope that "I" is a keyword and not a macro, as the OP suggested.

Regards,

Paul McKenzie

It's a macro.

See 7.3.1 - 4 (p170)
http://www.open-std.org/jtc1/sc22/WG...docs/n1256.pdf

gg

Quote:

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Originally Posted by Codeplug

It's a macro.

See 7.3.1 - 4 (p170)
http://www.open-std.org/jtc1/sc22/WG...docs/n1256.pdf

gg

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Yikes. I wonder if the language authors were tired that day?

Regards,

Paul McKenzie

Quote:

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Originally Posted by 2kaud

Do you mean setting real and imaginary parts separately like this?

Code:

---

#include <iostream>
#include <complex>
using namespace std;

int main()
{
const double fl = 2, Fs = 3;
const double PI = 3.1416;

typedef complex<double> Compnum;

Compnum com1(0, fl/Fs * 2 * PI);  //This gives an imaginary number ie 0 + i*fl/Fs * 2 * PI

Compnum com2 = exp(com1);

Compnum com3 (3, 4);

        cout << com3 << endl << com2 << endl;

        com3 = Compnum(real(com3), 6);
        com2 = Compnum(2, imag(com2));

        cout << com3 << endl << com2 << endl;
        return 0;
}

---

This produces the output

Code:

---

(3,4)
(-0.499992,-0.86603)
(3,6)
(2,-0.86603)

---

where the imaginary part of com3 has been set directly keeping the real part and the real part of com2 has been set directly keeping the imaginary part.

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Exactly! It worked perectly now. Thanks a lot!!!