CODEWITHSUNDEEP
iphonecobjective-cdouble
choise
choise

Reputation: 25244

floor double by decimal place

i want to floor a double by its decimal place with variable decimal length (in iphone sdk).

here some examples to show you what i mean

NSLog(@"%f",[self floorMyNumber:34.52462 toPlace:2); // should return 34.52
NSLog(@"%f",[self floorMyNumber:34.52662 toPlace:2); // should return 34.52

NSLog(@"%f",[self floorMyNumber:34.52432 toPlace:3); // should return 34.524
NSLog(@"%f",[self floorMyNumber:34.52462 toPlace:3); // should return 34.524

NSLog(@"%f",[self floorMyNumber:34.12462 toPlace:0); // should return 34.0
NSLog(@"%f",[self floorMyNumber:34.92462 toPlace:0); // should return 34.0

any ideas how to do this?

solution

-(double)floorNumberByDecimalPlace:(float)number place:(int)place {
    return (double)((unsigned int)(number * (double)pow(10.0,(double)place))) / (double)pow(10.0,(double)place);
}

Upvotes: 2

Views: 1964

Answers (4)

zneak
zneak

Reputation: 138051

Multiply it by 10^(decimal places), cast it to an integer, then divide it by 10^(decimal places).

double floorToPlace(double number, int places)
{
    int decimalPlaces = 1;
    for (int i = 0; i < places; i++) divideBy *= 10;

    return (int)(number * decimalPlaces) / (double)decimalPlaces;
}

Upvotes: 0

R.. GitHub STOP HELPING ICE
R.. GitHub STOP HELPING ICE

Reputation: 215261

Use sprintf (or better snprintf) to format it to a string then crop the end of the string.

Upvotes: 0

Quonux
Quonux

Reputation: 2991

Another solution:

placed is 10 (Example: 13.1), 100 (Example: 12.31) and so on

double value = (double)((unsigned int)(value * (double)placed)) / (double)placed

Upvotes: 1

arsenm
arsenm

Reputation: 2933

If you're just rounding them for the purpose of printing them, you do this with the standard printf format specifiers. For example, instead of "%f", to print 3 decimals you could use "%.3f"

Upvotes: 0

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