pow() doesnt return a double?

This is a discussion on pow() doesnt return a double? within the C++ Programming forums, part of the General Programming Boards category; Code: #include <iostream.h> #include <stdlib.h> #include <math.h> int main() { double result, x = 3.0, y = 2.0; result = ...

  1. #1
    Registered User FloatingPoint's Avatar
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    pow() doesnt return a double?

    Code:
    #include <iostream.h>
    #include <stdlib.h>
    #include <math.h>
    
    int main()
    {
          
          double result, x = 3.0, y = 2.0;
          result = pow(x, y);
    
          cout << result << endl;
    
          system("PAUSE");
          return 0;
    }

    The above gives me a result of 9 instead of 9.0
    as the book here says.

    Same thing w/ abs() or fabs() or floor() etc. The arguments are doubles but the value returned are integers.

    I did something wrong or do I need to use the "cout.setf....cout.precision" thingy, but this book doesnt say anything abt it.

    Thanx.

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  3. #3
    Registered User major_small's Avatar
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    Re: pow() doesnt return a double?

    Originally posted by FloatingPoint
    The above gives me a result of 9 instead of 9.0
    as the book here says.
    the computer will truncate any extra zeroes... set precision to 1 if you want them to show up... it truncates them at a sig digit because you don't want 9.00000000000000 to show up...
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  4. #4
    Comment your source code! Lynux-Penguin's Avatar
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    Code:
    #include <iostream.h>
    #include <iomanip.h>
    #include <math.h>
    int main()
    {
    	double result, x=3.0,y=2.0;
    	result = pow(x,y);
    	cout.setf(ios::fixed);
    	cout.precision(5);
    	cout<<result<<endl;
    	return 0;
    }
    Try this...

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  5. #5
    Cat without Hat CornedBee's Avatar
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    Or rather this:
    #include <iostream>
    #include <iomanip>
    #include <cmath>
    using namespace std;
    int main()
    {
    double result, x=3.0,y=2.0;
    result = pow(x,y);
    cout.setf(ios::fixed);
    cout.precision(5);
    cout<<result<<endl;
    return 0;
    }
    All the buzzt!
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  6. #6
    Registered User FloatingPoint's Avatar
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    Thanx all.

    I tried

    double result = 9.0;
    cout << result << endl;


    and it gave me a 9.

    Is this is how it's supposed to be? I mean the only way is to use that "cout.setf.....precision" block?

    Thanx.

  7. #7
    Registered User FloatingPoint's Avatar
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    Re: Re: pow() doesnt return a double?

    Originally posted by major_small
    the computer will truncate any extra zeroes... set precision to 1 if you want them to show up... it truncates them at a sig digit because you don't want 9.00000000000000 to show up...
    Yea, I guess so.

    Thanx again.
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  8. #8
    Registered User FloatingPoint's Avatar
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    Corned Bee;

    Yours flashes off the screen too fast. How do I put a "press any key to continue" there?

    #include <stdlib.h> or <stdlib> doesnt seem to work.

    Thanx.
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  9. #9
    Cat without Hat CornedBee's Avatar
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    Would be <cstdlib>, but...

    a) When launching from within VC++ it gets stopped anyway.
    b) The usual console app is launched from the command line where you have a console window that stays.
    All the buzzt!
    CornedBee

    "There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
    - Flon's Law

  10. #10
    Registered User FloatingPoint's Avatar
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    Included that and I'm using Dev C++ 4 but it doesnt stay.
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    and I'll cast mine all over thee
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  11. #11
    Cat without Hat CornedBee's Avatar
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    Of course it doesn't. No header file makes the app stay by itself.

    Add
    system("pause");
    (or std::system("pause"))
    directly before the return.
    All the buzzt!
    CornedBee

    "There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
    - Flon's Law

  12. #12
    Registered User major_small's Avatar
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    header files don't but some compilers will...
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  13. #13
    ¡Amo fútbol!
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    use cin.get()

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  15. #15
    Super Moderator VirtualAce's Avatar
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    pow() most certainly does return a double. It leaves the result of the operation in st(0). If your not getting a double then your value is being converted to an integer via a FISTP or similar FPU opcode.

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