Ok I'm stuck with a double to float error

This is a discussion on Ok I'm stuck with a double to float error within the C Programming forums, part of the General Programming Boards category; Here's the snippet of code that I'm having problems with: Code: int customernumber; float waterlevel; float previouslevel; float totalwater; float ...

  1. #1
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    Ok I'm stuck with a double to float error

    Here's the snippet of code that I'm having problems with:

    Code:
                   
    
                    int            customernumber;
    	float	waterlevel;
    	float	previouslevel;
    	float	totalwater;
    	float	totalbill;
    	float	amountowed;
    
    
    	printf("Enter customer number\n" );
    
    	scanf( "%d" ,  &customernumber );
    
    	printf("Enter current water level\n" );
    
    	scanf("%f" , &waterlevel );
    
    	printf("Enter previous water level\n" );
    
    	scanf("%f", &previouslevel );
    
    	totalwater = waterlevel - previouslevel;
    
    	totalbill = 30 + (totalwater/1000  * .55);
    
    	amountowed = totalbill;
    I keep getting this warning "conversion from double to float, possible loss of data" for this line

    totalbill = 30 + (totalwater/1000 * .55);

    I dont understand what it could mean, everything is declared as float ( I, obviously, made sure of that), if anyone has any idea what's wrong with this line I would really appreciate it if ya could share it with me.
    Thank you very much.
    Last edited by Extropian; 06-06-2005 at 11:24 AM.

  2. #2
    and the hat of wrongness Salem's Avatar
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    .55 by itself is a double constant.
    Since the rest of the expression is float, I think it's this one which making the whole of the right hand side into a double expression.

    So when you perform the assignment, the now double expression on the right is being converted to a float.

    .55F is the way to define a float constant.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  3. #3
    Frequently Quite Prolix dwks's Avatar
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    Or you could just add a cast:

    Code:
    totalbill = (float) (30 + (totalwater/1000 * .55));
    [EDIT]
    Or maybe declare everything as double and not as float.

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