I have an array of strings that are fractions (1/3, 2/5) etc. I need to take these strings and use them as doubles for calculations. The fractions go into the arrays as strings. Why isn't the below code working?
NSString *localString = [array objectAtIndex:1];
double NewDouble = [localString doubleValue];
I get the first int in each string (1 instead of .333 & 2 instead of .4 from above).
I'm missing something easy and it's driving me crazy.
Thanks
You cannot take a NSStringrepresenting a fraction and demand its doubleValue. You have to split the string and calculate the fraction manually.
Related
I have a float var1 = cashInHandAmount = 4.73000002
I simply want as:
var2 = 4.73.
I have tried like this:
NSString *floatString = [NSString stringWithFormat:#"%.02f",cashInHandAmount];//it prints 4.73
[self.editcash setMaxValue:[floatString floatValue]];//but it again sets 4.73000002 why?
can you guys please help me regarding this?
%f simply rounds for the output. Transforming a float value into a string and back does not work, if the exact value (i. e. 4.73) has no representation in the float format. So transforming it back will "round" the stored value 4.73 into the float format, which is obviously 4.730…02.
You should rarely use (binary, IEEE) floats for financial calculating. Financial values (amount of money) is in most cases an integral value of cents, but no float value of dollars (or whatever). Additionally you can think about using NSDecimal and NSDecimalNumber to ensure, that every value with two digits of precision is storable in the format.
Edit:
float f = 4.73000002;
float rounded = roundf(f * 100.0f) / 100.0f;
NSLog(#"%10.10f", rounded);
outputs:
2014-07-01 10:25:48.653 xctest[596:303] 4.7300000191
It is difficult to check, but probably float can not represent 4.73 exactly. The nearest representable value is 4.7300000191. This is what I said: A rounded decimal representation is not always a possible "binary float" representation. You will face that problem with many values.
Try this :
float var1 = 4.73000002;
NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
formatter.numberStyle = NSNumberFormatterDecimalStyle;
formatter.maximumFractionDigits = 2; //Set number of fractional digits
NSNumber *num = [NSNumber numberWithFloat:var1];
NSString *roundedNum = [formatter stringFromNumber:num];
DLOG(#"Answer : %#", roundedNum);
If you want truncate all other decimals you can declare a simple method like this:
- (float)sanitizeFloat:(float)value
{
float newValue = [[NSString stringWithFormat:#"%.2f",value] floatValue];
return newValue;
}
and then
float aFloat = 45.070809;
NSLog(#"%f",[self sanitizeFloat:aFloat]);
In your case:
[self.editcash setMaxValue:[self sanitizeFloat:cashInHandAmount]];
The output will be 45.070000
If you're working with monetary amounts that have fixed decimal places, you should always use NSDecimal or NSDecimalNumber - you shouldn't use floats at all, as they are inexact.
You could use:
-[NSDecimalNumber decimalNumberWithString:]
to create your number, and there are many methods for working with NSDecimalNumbers - see Apple's docs or NSDecimalNumber.h for details.
I'm trying to create NSDecimalNumber with simply format like: 123.00 with two fractional digits after dot, always. I tried use the NSFormatter and many other ways like converting float from string and creating then NSDecimalNumber from this string, but it's not working.
The problem is that I need only NSDecimalNumber in this format, not NSString or any other.
Thanks for any advice,
Paul
You may get idea from this.
float num = 123.1254546;
NSString *str = [NSString stringWithFormat:#"%.2f",num];
NSLog(#"%.2f %#",num,str);
I think you simply need to do Type Casting operation for Two times as bellow
float value = 123.562;
int myDigit = value;
it gives value 123 in myDigit variable
NSLog(#"MyDigit in Decimal = %d",myDigit);
Output is MyDigit in Decimal = 123
now if you want output like 123.000 then simply write as bellow
float valueWithZiro = myDigit;
NSLog(#"MyDigit with 000 == %3f",valueWithZiro);
Output is MyDigit in Decimal = 123.000
NSDecimalNumber, like NSNumber, cannot contain formatting information. The object structure simply doesn't support it. It represents a number, not the way the number is displayed.
You can convert it to a formatted NSString (which you say you don't want). But you can't do what you're asking.
You convert it to a formatted NSString using an NSNumberFormatter. It's the object that allows you to specify the decimal and thousands separators, number of decimal places to display, the currency symbol, etc.
Maybe you were looking to store a NSNumberDecimal with just two digits after the fraction?
If so NSDecimalNumberBehaviors is your friend.
I had a similar need and used the following:
self.decimalHandlingBehaviorForApp = [NSDecimalNumberHandler
decimalNumberHandlerWithRoundingMode:NSRoundUp
scale:2 raiseOnExactness:NO
raiseOnOverflow:NO raiseOnUnderflow:NO
raiseOnDivideByZero:YES];
Edit: added example of using it
// update the taxable total first
self.cartTaxableTotal = [self.cartTaxableTotal decimalNumberByAdding:itemAdded.priceOfItem
withBehavior:self.decimalHandlingBehaviorForApp];
I have a double that I need only the value of everything before the decimal point.
Currently I am using
NSString *level = [NSString stringWithFormat:#"%.1f",doubleLevel];
but when given a value of 9.96, this returns "10". So it is rounding. I need it to return only the "9". (note - when the value is 9.95, it correctly returns the "9" value.)
Any suggestions?
Thank You.
Simply assign the float/double value to a int value.
int intValue = doubleLevel;
Cast that baby as an int.
int castedDouble = doubleLevel;
Anything after the . in the double will be truncated.
9.1239809384 --> 9
123.90454980 --> 123
No rounding, simple truncation.
If you want to keep it as a float:
CGFloat f = 9.99;
f = floorf(f);
there are quite a variety of floor and round implementations.
they have been around since UN*X, and are actually part of those low-level libraries, be they BSD, Posix, or some other variety - you should make yourself familiar with them.
there are different versions for different "depths" of floating point variables.
NSString *level = [NSString stringWithFormat:#"%d",doubleLevel];
I have an NSArray in which I would like to store double values. I defined it as follow
NSMutableArray *setOfDoubles;
I add the elements as follow
NSNumber *num;
num = [NSNumber numberWithDouble:someDouble];
[setOfDoubles addObject:num];
And I read the element as follow
num = [setOfDoubles lastObject];
[setOfDoubles removeLastObject];
doubleValueToUse = [num doubleValue];
My problem is sometimes (Not always), for example when num (as an object) is 5.1, doubleValueToUse (as a double value) is 5.099999999999996. The way I figured num (as an object) is 5.1 is that I debug and when I am hovering the mouse on top of num on the line num = [setOfDoubles lastObject]; it shows 5.1 but after doubleValue conversion it becomes the number I mentioned. Does anybody know why is this happening?
Not every number can be accurately represented using a float variable. For example, you can't precisely represent, say, 1/3 using a finite number of digits in our common decimal (base-10) system, but in ternary (base-3), it would be just 0.1. Similarly, the numbers you can write with a finite number of digits in decimal, may not necessarily have the finite number of digits in their binary representation, hence the error.
A few links on the topic if you are interested:
http://floating-point-gui.de/basic/
http://www.mathworks.com/support/tech-notes/1100/1108.html
http://download.oracle.com/docs/cd/E19957-01/806-3568/ncg_goldberg.html
This is normal for float values.
If you want to save initial (same) representation of float numbers in all places of your code, you can save them, for example, in NSString. When you will need float number you will just write [NSString floatValue];. But it is not effective if you have large amount of float values.
In an iphone app, I have 2 large numbers stored in NSStrings, and I want to figure out the float number that is achieved by dividing them.
Right now, I have:
unsigned long long number = [string1 longLongValue];
unsigned long long number2 = [string2 longLongValue];
float percent = number/number2;
[textField setText:[NSString stringWithFormat: #"%f%%",percent]];
(I assume I have to use "unsigned long long" instead of ints because the numbers in the NSStrings are pretty high- the first one is 309,681,754 and the second is 6,854,433,820)
However, after I do this, I always get 0% in the text field. What am I doing wrong?
Thanks for any help in advance.
You are dividing integers. That always results in an integer.
What you need to do is to cast them to floats before dividing. This should work:
float percent = (float)number / (float)number2;