if( 3.14 == inf ){} produces compiler error

This is a discussion on if( 3.14 == inf ){} produces compiler error within the C++ Programming forums, part of the General Programming Boards category; The code Code: cout << " max = " << max << endl; outputs Code: max = inf The code ...

  1. #1
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    if( 3.14 == inf ){} produces compiler error

    The code
    Code:
    cout <<  " max = " << max << endl;
    outputs
    Code:
     max = inf
    The code
    Code:
    if( 3.14 == inf )
    or specifically the code
    Code:
    if( max == inf )
    won't compile. How can I determine if max is equal to infinity?

  2. #2
    Registered User IdioticCreation's Avatar
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    What is inf originally defined as? and are you using float?

  3. #3
    MFC killed my cat! manutd's Avatar
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    What's the exact error?
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  4. #4
    carry on JaWiB's Avatar
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    the numeric_limits<> class has a has_infinity member and an infinity() function
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  5. #5
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    Quote Originally Posted by manutd
    What's the exact error?
    Code:
    Rfilt.cpp: In member function `void Cwn::bounds()':
    Rfilt.cpp:299: error: `inf' undeclared (first use this function)
    Rfilt.cpp:299: error: (Each undeclared identifier is reported only once for
       each function it appears in.)

  6. #6
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    Quote Originally Posted by IdioticCreation
    What is inf originally defined as? and are you using float?
    "inf" is the value of "max." Max is a double.

  7. #7
    MFC killed my cat! manutd's Avatar
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    SHow us your complete code.
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    Quote Originally Posted by manutd
    SHow us your complete code.
    I'll show you the member function.
    Code:
    void Cwn::bounds()
    {
    	long i;
    	double max = 0.0, min = 0.0;
    
    	
    	for ( i = 0; i < samp2; i++)
    	{	
    		if ( max < array2[i] )
    			max = array2[i];
    		if ( min > array2[i] )
    			min = array2[i];
    	}
    
    	cout << "from bounds(): " <<  " max of array2 = " << max << endl;
    	cout << "from bounds(): " <<  " min of array2 = " << min << endl;
    
    	if(  max == inf ) 
    	{
    		cout << "Error: Filter unstable. Try setting -qual to a higher value." << endl;
    		exit(0);
    	}
    	
    	
    }

  9. #9
    MFC killed my cat! manutd's Avatar
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    More. Attach a text file if needed.
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  10. #10
    Registered User Tonto's Avatar
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    >> the numeric_limits<> class has a has_infinity member and an infinity() function

    http://www.tacc.utexas.edu/resources...r/num_5679.htm

    Code:
    Example
    
    //
    // limits.cpp
    //
     #include <limits>
    
    
     int main() 
     {
        numeric_limits<float> float_info;
        if (float_info.is_specialized && float_info.has_infinity)
        {
          // get value of infinity 
          float finfinity=float_info.infinity(); 
        }
        return 0;
     }

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  11. #11
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    You still didn't say what inf actually is. You say it is the value of max, but how is it declared/defined. There is no "inf" in C++, so if you are using it you have to define it yourself. Show the code where you do that.

  12. #12
    S Sang-drax's Avatar
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    Isn't it obvious? He doesn't declare it.

    Use Tonto's suggestion to fix the problem.
    Last edited by Sang-drax : Tomorrow at 02:21 AM. Reason: Time travelling

  13. #13
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    >> Isn't it obvious? He doesn't declare it.
    Obviously it is not declared in the posted code, but thetinman indicated that it was assigned to max, which you can assume he or she might think is being done elsewhere. There is a misunderstanding there that needs to be fixed before JaWiB's and Tonto's suggestions can be used.

  14. #14
    Crazy Fool Perspective's Avatar
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    He said "inf" was output to the console, so he wrote it into his code. "inf" is not globally defined, it is not a variable. You have to define it as being the maximum value yourself.

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