I am trying to save a long long number (received as a string) such as '80182916772147201' into an NSNumber.
NSNumberFormatter * f = [[NSNumberFormatter alloc] init];
[f setNumberStyle:NSNumberFormatterBehaviorDefault];
[item setObject:[f numberFromString:#"80182916772147201"] forKey:#"theID"];
[f release];
When I NSLog this out, assuming the string was '80182916772147201' I get:
NSLog(#"%lld", [[item objectForKey:#"theID"] longLongValue]);
Returns: '80182916772147200' - Note the rounded down final digit.
What am I doing wrong?
The problem is that NSNumberFormatter has decided to represent that number as a floating-point number. To force it to use integers only:
[f setAllowsFloats:NO];
Can you try this?
NSString *numStr = [NSString stringWithFormat:#"%llu", [myNum unsignedLongLongValue]];
This makes a few reasonable assumptions such as numStr will only contain numeric digits and it contains a 'valid' unsigned long long value. A drawback to this approach is that UTF8String creates what essentially amounts to [[numStr dataUsingEncoding:NSUTF8StringEncoding] bytes], or in other words something along the lines of 32 bytes of autoreleased memory per call. For the vast majority of uses, this is no problem what-so-ever.
For an example of how to add something like unsignedLongLongValue to NSString that is both very fast and uses no autoreleased memory as a side effect, take a look at the end of my (long) answer to this SO question. Specifically the example implementation of rklIntValue, which would require only trivial modifications to implement unsignedLongLongValue.
Related
I have a NSString with me. This NSString is obtained from a Voice engine. The voice input is converted to native NSString.
See the following string:
"Set heat to thirty two degree"
Is there any way to get this converted to
"Set heat to 32 degree"
If there are some third party library that does this conversion, it would be really helpful. Otherwise I will have to create a complex logic to get this done it seems.
And that's where a forgotten NSNumberFormatter can show what it's capable of doing.
After you parsed your input string (using regular expression magic or NSString's componentsSeparatedByString:, I'll not be discussing that step) and obtained the spell-out number, you can use NSNumberFormatter's NSNumberFormatterSpellOutStyle to quickly convert your string into a number:
NSString *obtainedDegreesString = #"thirty-two";
NSNumberFormatter *spellOutFormatter = [[NSNumberFormatter alloc] init];
[spellOutFormatter setLocale:[NSLocale currentLocale]]; // or whatever locale you want
[spellOutFormatter setNumberStyle:NSNumberFormatterSpellOutStyle];
NSNumber *degreesNumber = [spellOutFormatter numberFromString:obtainedDegreesString];
NSLog(#"%d", degreesNumber.intValue); // logs 32
But warning - you have to convert strings like "thirty two" to "thirty-two" (the correct English numerals) for your formatter to work - passing "thirty two" results in 3002! Your users probably don't want to burn in 3002 degrees :P You can achieve that using another regular expression, I suppose.
How can I remove the all the characters after the decimal point.
Instead of 7.3456, I would just like 7.
This is what I do to get the number so far with decimal places.
[NSString stringWithFormat:#" %f : %f",(audioPlayer.currentTime),(audioPlayer.duration) ];
Many Thanks,
-Code
You can specify what you want using format string :
[NSString stringWithFormat:#" %.0f : %.0f", (audioPlayer.currentTime),
(audioPlayer.duration)];
If you want this for display, use an NSNumberFormatter:
double sevenpointthreefourfivesix = 7.3456;
NSNumberFormatter * formatter = [[NSNumberFormatter alloc] init];
[formatter setMaximumFractionDigits:0];
NSLog(#"%#", [formatter stringFromNumber:[NSNumber numberWithDouble:sevenpointthreefourfivesix]]);
2011-12-20 20:19:48.813 NoDecimal[55110:903] 7
If you want a value without the fractional part, use round(). If you want the closest integer value not greater than the original value, use floor().
floorf() is the function you're looking for.
you are after
[NSString stringWithFormat:#" %.00f : %.00f",(audioPlayer.currentTime),(audioPlayer.duration) ];
When formatting float you can tell the precision by the number before the f
Cast to int:
[NSString stringWithFormat:#" %i : %i",(int)(audioPlayer.currentTime),(int)(audioPlayer.duration) ];
Casting like this always rounds down (eg: just removes everything after the decimal place). This is what you asked for.
In the case of rounding to the NEAREST whole number you want to add 0.5 to the number
[NSString stringWithFormat:#" %i : %i",(int)(audioPlayer.currentTime+0.5f),(int)(audioPlayer.duration+0.5f) ];
This will round to the nearest whole number. eg: 1.2 becomes 1.7 and casting to int makes 1. 3.6 becomes 4.1 and casting makes 4. :)
Why not just cast the audioPlayer.currentTime to an integer before you use stringWithFormat?
[NSString stringWithFormat:#"%d", (int)(audioPlayer.currentTime)];
All you need to do is type-cast the double to an int, like so: int currentTime_int = (int)audioPlayer.currentTime;.
You can use this same approach for the other variable.
Many of the shorter answers here will work correctly. But if you want your code to be really clear and readable, you might want to explicitly specify your desired conversion from float to int, such as using:
int tmpInt = floorf(myFloat); // or roundf(), etc.
and then separately specifying how you want the integer formated, e.g.
... stringWithFormat:#"%d", tmpInt ... // or #"%+03d", etc.
instead of assuming that an inline cast shows what you want.
You may also use
double newDvalue =floor(dValue);
it will remove all the decimals point
using %.0f for string format will be good also
I have 2 NSArray (Mutable, actually) that I am trying to convert to a C-style double array for a c routine i am passing them to.
Here is my Objective-C routine:
NSMutableDictionary *childDictionary = [myParentDictionary objectForKey:resort_code];
latitudeArray = [childDictionary objectForKey:#"lat"];
longitudeArray = [childDictionary objectForKey:#"lon"];
int nvert = [latitudeArray count];
double laArray[nvert];
double loArray[nvert];
for(int i=0; i<nvert; i++) {
double dLat = [[latitudeArray objectAtIndex:i]doubleValue];
double dLon = [[longitudeArray objectAtIndex:i]doubleValue];
laArray[i] = dLat;
loArray[i] = dLon;
}
This takes upwards of 3-8 seconds on the 3G iPhone (instantaneous on the simulator -- yet another reason to test on the device )
is there faster way? I have to end up with laArray[i] and loArray[i] as c-style arrays of doubles.
(to expand on the question for the benefit of a commenter):
Each array consists of #"38.448745" (lat) and #"-122.9847684" (lon) style content. I do this cos to be pushed onto an NSArray, the lat and lon need to be objects. I simply used:
[latitudeArray addObject:[NSString stringWithFormat: #"%.10f",dlat]];
[longitudeArray addObject:[NSString stringWithFormat: #"%.10f",dlon]];
I suppose I could change that to:
[latitudeArray addObject:[NSNumber numberWithDouble: #"%.10f",dlat]];
[longitudeArray addObject:[NSNumber numberWithDouble: #"%.10f",dlon]];
...which may reduce the conversion time of
double dLat = [[latitudeArray objectAtIndex:i]doubleValue];
but wouldn't I still need that exact line to convert from NSString to double? It just may work faster?
thx
dlat is a double, right?
So instead of:
[latitudeArray addObject:[NSString stringWithFormat: #"%.10f",dlat]];
Do:
[latitudeArray addObject:[NSNumber numberWithDouble:dlat]];
They both respond to doubleValue but the NSNumber should not have to do any string parsing since it's stored as a numeric value already. And you never have to go to a string at all.
I suspect you have an array of strings like #"213.12385" that need to be parsed and converted when you call doubleValue on them. If that is where the issue is, the C arrays have nothing to with this.
Only thing I would add here is to throw Shark on this and see where it's spending it's time. If it's spending time in doubleValue find a different way to parse the strings with preprocessing in background or something. If it's in objectAtIndex: perhaps fast enumeration would help. If it's somewhere else entirely then you know it's not this snippet that's slow.
For the general case of converting an NSArray to a C array, you can use getObjects:. In this case, though, want you actually want is not to convert the NSArray, but to derive an array of doubles from an NSArray of some unspecified object type.
One obvious way to speed things up would be fast enumeration rather than sending a message to get the object for each iteration of the loop. I suspect the real solution, though, is outside your algorithm. The slowness probably comes from transforming whatever objects the array contains into doubles, in which case you'll need to find a way around that — maybe store doubles all along, maybe do the conversion in the background, etc. If you're creating the arrays yourself and there isn't some compelling reason for the objects to be strings, you should use NSNumbers instead. Those should be quite a bit faster.
The best solution is probably to make sure those values never end up in an NSArray as NSString values. I would attack this at the source.
So you edited your question and added that you are actually building those arrays. So why not use native arrays of doubles or floats from the start? I usually recommend against this but in your case it sounds like there is a huge performance gain.
Possibly using fast iteration, but I doubt that will really speed up your loop.
I have trouble when I have currency value
999999999999999999.99
From that value, I want to display it as String. The problem is that value always rounded to
1000000000000000000.00
I'm not expect that value rounded. I want the original value displayed. Do you have any idea how to solve this problem? I tried this code from some answer/turorial in stackoverflow.com :
NSMutableString *aString = [NSMutableString stringWithCapacity:30];
NSNumberFormatter *aCurrency = [[NSNumberFormatter alloc]init];
[aCurrency setFormatterBehavior:NSNumberFormatterBehavior10_4];
[aCurrency setNumberStyle:NSNumberFormatterCurrencyStyle];
[aCurrency setMinimumFractionDigits:2];
[aCurrency setMaximumFractionDigits:2];
[aString appendString:[aCurrency stringFromNumber:productPrice]];
//productPrice is NSDecimalNumber which is have value 999999999999999999.99
cell.textLabel.text = aString;
NSLog(#"the price = %#",cell.textLabel.text);
//it prints $1,000,000,000,000,000,000.00
[aCurrency release];
Unless you have very good reasons not to, it is generally best to keep currency values in a fixed-point format, rather than floating point. Ada supports this directly, but for C-ish languages what you do is keep the value in units of pennies, rather than dollars, and only do the conversion whenever you go to display it.
So in this case the value of productPrice would be 99999999999999999999 (cents). To display it, you'd do something like this (If this were C. I don't know the language):
int const modulus = productPrice % 100;
printf ("The price = %d.%d\n", (int) ((productPrice - modulus) / 100), modulus);
I'd also use an integer rather than a floating point variable to keep the value in almost all cases. It won't work in this case (even if you use a 64-bit integer) because your value is mind-bogglingly large. We're talking 1 million times larger than the US National Debt! If a dollar value that large ever makes sense for anything in my lifetime, we are all in big trouble.
Have you tried these:
* – setRoundingBehavior:
* – roundingBehavior
* – setRoundingIncrement:
* – roundingIncrement
* – setRoundingMode:
* – roundingMode
I have some string s that is locale specific (eg, 0.01 or 0,01). I want to convert this string to a NSDecimalNumber. From the examples I've seen thus far on the interwebs, this is accomplished by using an NSNumberFormatter a la:
NSString *s = #"0.07";
NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
[formatter setFormatterBehavior:NSNumberFormatterBehavior10_4];
[formatter setGeneratesDecimalNumbers:YES];
NSDecimalNumber *decimalNumber = [formatter numberFromString:s];
NSLog([decimalNumber stringValue]); // prints 0.07000000000000001
I'm using 10.4 mode (in addition to being recommended per the documentation, it is also the only mode available on the iPhone) but indicating to the formatter that I want to generate decimal numbers. Note that I've simplified my example (I'm actually dealing with currency strings). However, I'm obviously doing something wrong for it to return a value that illustrates the imprecision of floating point numbers.
What is the correct method to convert a locale specific number string to an NSDecimalNumber?
Edit: Note that my example is for simplicity. The question I'm asking also should relate to when you need to take a locale specific currency string and convert it to an NSDecimalNumber. Additionally, this can be expanded to a locale specific percentage string and convert it to a NSDecimalNumber.
Years later:
+(NSDecimalNumber *)decimalNumberWithString:(NSString *)numericString in NSDecimalNumber.
Based on Boaz Stuller's answer, I logged a bug to Apple for this issue. Until that is resolved, here are the workarounds I've decided upon as being the best approach to take. These workarounds simply rely upon rounding the decimal number to the appropriate precision, which is a simple approach that can supplement your existing code (rather than switching from formatters to scanners).
General Numbers
Essentially, I'm just rounding the number based on rules that make sense for my situation. So, YMMV depending on the precision you support.
NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
[formatter setFormatterBehavior:NSNumberFormatterBehavior10_4];
[formatter setGeneratesDecimalNumbers:TRUE];
NSString *s = #"0.07";
// Create your desired rounding behavior that is appropriate for your situation
NSDecimalNumberHandler *roundingBehavior = [NSDecimalNumberHandler decimalNumberHandlerWithRoundingMode:NSRoundPlain scale:2 raiseOnExactness:FALSE raiseOnOverflow:TRUE raiseOnUnderflow:TRUE raiseOnDivideByZero:TRUE];
NSDecimalNumber *decimalNumber = [formatter numberFromString:s];
NSDecimalNumber *roundedDecimalNumber = [decimalNumber decimalNumberByRoundingAccordingToBehavior:roundingBehavior];
NSLog([decimalNumber stringValue]); // prints 0.07000000000000001
NSLog([roundedDecimalNumber stringValue]); // prints 0.07
Currencies
Handling currencies (which is the actual problem I'm trying to solve) is just a slight variation on handling general numbers. The key is that the scale of the rounding behavior is determined by the maximum fractional digits used by the locale's currency.
NSNumberFormatter *currencyFormatter = [[NSNumberFormatter alloc] init];
[currencyFormatter setFormatterBehavior:NSNumberFormatterBehavior10_4];
[currencyFormatter setGeneratesDecimalNumbers:TRUE];
[currencyFormatter setNumberStyle:NSNumberFormatterCurrencyStyle];
// Here is the key: use the maximum fractional digits of the currency as the scale
int currencyScale = [currencyFormatter maximumFractionDigits];
NSDecimalNumberHandler *roundingBehavior = [NSDecimalNumberHandler decimalNumberHandlerWithRoundingMode:NSRoundPlain scale:currencyScale raiseOnExactness:FALSE raiseOnOverflow:TRUE raiseOnUnderflow:TRUE raiseOnDivideByZero:TRUE];
// image s is some locale specific currency string (eg, $0.07 or €0.07)
NSDecimalNumber *decimalNumber = (NSDecimalNumber*)[currencyFormatter numberFromString:s];
NSDecimalNumber *roundedDecimalNumber = [decimalNumber decimalNumberByRoundingAccordingToBehavior:roundingBehavior];
NSLog([decimalNumber stringValue]); // prints 0.07000000000000001
NSLog([roundedDecimalNumber stringValue]); // prints 0.07
This seems to work:
NSString *s = #"0.07";
NSScanner* scanner = [NSScanner localizedScannerWithString:s];
NSDecimal decimal;
[scanner scanDecimal:&decimal];
NSDecimalNumber *decimalNumber = [NSDecimalNumber decimalNumberWithDecimal:decimal];
NSLog([decimalNumber stringValue]); // prints 0.07
Also, file a bug on this. That's definitely not the correct behavior you're seeing there.
Edit: Until Apple fixes this (and then every potential user updates to the fixed OSX version), you're probably going to have to roll your own parser using NSScanner or accept 'only' double accuracy for entered numbers. Unless you're planning to have the Pentagon budget in this app, I'd suggest the latter. Realistically, doubles are accurate to 14 decimal places, so at anything less than a trillion dollars, they'll be less than a penny off. I had to write my own date parsing routines based on NSDateFormatter for a project and I spent literally a month handling all the funny edge cases, (like how only Sweden has the day of week included in its long date).
See also Best way to store currency values in C++
The best way to handle currency is to use an integer value for the smallest unit of the currency, i.e. cents for dollars/euros, etc. You'll avoid any floating point related precision errors in your code.
With that in mind, the best way to parse strings containing a currency value is to do it manually (with a configurable decimal point character). Split the string at the decimal point, and parse both the first and second part as integer values. Then use construct your combined value from those.