In my calculator app, I am trying to display a "double" value in a UILabel. However, the value always has more zeros than it needs. For example, 64 is displayed as 64.000000, 4.23 is displayed as 4.230000, etc.
How can I make it display only as many decimal places as fits?
vector<Token> postfix; // create empty postfix vector
infixToPostfix(infix, postfix); // call inToPost to fill up postfix vector from infix vector
answer = postFixEvaluate(postfix); // evaluate expression
expString.clear();
expNSString = [NSString stringWithFormat:#"%f", answer]; // convert "answer" to NSString
displayScreen.text = expNSString; // display answer in UIlabel "displayScreen"
As mentioned in the [NSString stringWithFormat:] class reference:
Parameters
format A format string. See “Formatting String Objects” for
examples of how to use this method, and “String Format Specifiers” for
a list of format specifiers. This value must not be nil.
and following the first link, one of the first examples is:
NSString *string1 = [NSString stringWithFormat:#"A string: %#, a float: %1.2f",
#"string", 31415.9265]; // ^
// string1 is "A string: string, a float: 31415.93"
You need to learn to think for yourself. Read the documentation!
This question is a little old, but did you try %g? This will produce scientific notation in some cases:
64-bit floating-point number (double), printed in the style of %e if the exponent is less than –4 or greater than or equal to the precision, in the style of %f otherwise.
But, as it says, you can control this to some extent using the precision field: if your numbers are large, you will need to increase the precision to avoid scientific notation. If your numbers are small, then I think there is nothing you can do about it when using %g.
I get this output:
64.0 -> "64"
64.1 -> "64.1"
64.15555 -> "64.1556" // default precision is 6
Related
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 am trying to convert an int to a string in objective-C.
I read the other questions on SO about converting ints to strings, and I tried this method in my code:
-(void)setCounter:(int)count
{
counterText.text = [NSString stringWithFormat:#"%d",count];
}
However, if I want to display a number like '01' the 0 is taken out of the conversion and only '1' is displayed. Is there a workaround?
There is no such number as 01. If you write
int count = 01;
it is compiled equivalently to
int count = 1;
In fact, be careful: 07 is equivalent to 7, but 011 is equivalent to 9!
What you can do is ask stringWithFormat: to give you the zero-padding:
[NSString stringWithFormat:#"%02d",count]
should give you "02" if count is 2. To deconstruct it:
% - interpolate the next value here
0 - pad it to the width by placing zeroes on the left side
2 - width is 2 characters
d - it will be an integer. Do it now.
If you want a different format to the one shown, use it:
counterText.text = [NSString stringWithFormat:#"%02d",count];
There are a huge range of possibilities with the format string.
if any number start from 0 then Its a octal representation (0 - 7). you can add zero explictly using below line.
counterText.text = [NSString stringWithFormat:#"0%d",count];
Check out..
NSNumber +numberWithInt
and then:
NSNumberFormatter -setMinimumIntegerDigits
and then get the string representation with:
NSString -stringFromNumber
i have a one application i know The range of a double is **1.7E +/- 308 (15 digits).**but in my application i have to devide text box 's value to 100.0 my code is
double value=[strPrice doubleValue]/100.0;
NSString *stramoount=[#"" stringByAppendingFormat:#"%0.2f",value ];
when i devide 34901234566781212 by 100 it give me 349012345667812.12 but when i type
349012345667812124 and devide by 100 it give me by 100 it give me 3490123456678121.00 which is wrong whether i change datatype or how can i change my code
The number 349012345667812124 has 18 decimal digits. the double format only provides slightly less than 16 decimal digits of precision (the actual number is not an integer because the format's binary digits do not correspont directly to decimal ones). Thus it is completely expected that the last 2 or 3 digits cannot be represented accurately, and it already happens when the literal "349012345667812124" is parsed to the double format, before any calculations happen.
The fact that you get the expected result with the number 34901234566781212 means nothing; it just happens to be close enough to the nearest value the double format can represent.
To avoid this problem, use the NSDecimal or NSDecimalNumber types.
Use
NSDecimalNumber * dec=[[NSDecimalNumber decimalNumberWithString:value.text locale: [NSLocale currentLocale]] decimalNumberByDividingBy:[NSDecimalNumber decimalNumberWithString:#"100" locale:[NSLocale currentLocale]]];
NSLog(#"%#",dec);
instead of Double
I have made a quadratic equation solver for the iPhone and when the text box is clicked, my own custom keypad appears. I have a button that changes whether the number is positive or negative. Right now I what happens is that when the button is pressed (0 - current value of text) is what is displayed in the text box, so if the number is positive, it will become negative and if it is negative it will become positive. I am having some problems doing this so what I wanted to is to put a minus sign at the beginning of the string if the number is positive and if the number is negative, the minus sign will be removed. Can anyone give me guidance on this?
Instead of negating using a mathematical function I assigned a NSMutableString to my UITextField then I inserted a "-" sign using insertString:atIndex: then I reassigned the changed string to my UITextField. To toggle between positive and negative, I created an if function so if the float value of my textfield is greater or equal to 0, then an "-" is inserted but if the float value of my text field is less than zero, the "-" is removed using deleteCharactersInRange. Here is my code as it stands:
- (IBAction)positivity{
NSMutableString *a = [NSMutableString stringWithString:aVal.text];
if([aVal.text floatValue]>=0){
[a insertString: #"-" atIndex: 0];
aVal.text = a;
}
else if([aVal.text floatValue]<0){
NSRange range = {0,1};
[a deleteCharactersInRange:range];
aVal.text = a;
}
}
aVal is the name of the UITextField that i am changing.
An alternative to the straight string approach is to not use a string. A while back I wrote a graphing calculator for iPhone that stored the equation internally in an NSMutableArray of NSStrings. Each slot in the array corresponded to one element in the equation, such as "x", "^", "sin(", etc.
When I needed to negate the equation, it was much easier to tell the array to insertObject:#"-" atIndex:0 than to try and insert it directly into the string. Then whenever the array was changed, I just remade the equation string like this:
NSString * newEquation = [equationElements componentsJoinedByString:#""];
While you could directly manipulate a string representation of a numeric value, such an approach is a bad idea. Not only is it less efficient than other alternatives, but potentially incorrect. (For example, #Ken's answer would result in two minus signs.)
What you probably want to do is negate the numeric value (just multiply it by -1, or subtract it from 0 as you suggested) and reflect that change in the interface (you mention a text box).
If you're using standard Cocoa controls (which inherit from NSControl, as NSTextField does) I suggest using -[NSControl setIntegerValue:] to change the text of the text field. If you (can) break up your UI well and have a text field for each variable in the quadratic equation, this should be fairly simple. (If you're using something other than an integer value, use something like -setDoubleValue: or -setFloatValue: instead.)
If you must create your own string beforehand, using an integer format specifier will display a "-" sign automatically if appropriate. Be sure to use %ld instead of %d (thanks, #Peter!) as the format specifier for NSInteger values to avoid possibly truncating values larger than 32-bit. For example:
NSString *result = [NSString stringWithFormat:#"%ld", nsIntegerValue];
In a more general sense, if you need to insert a dynamically-obtained string (not just something for which you can create a format string at compile time) you can also use an NSMutableString and its methods -appendString: and -insertString:atIndex: as well.