Hi I have made an IOS app that converts binary, hexadecimal and decimal values. It all works fine except for my decimal to binary conversion. Here is what I have. It returns 0s and 1s but far too many. Can anyone tell me why this is or help me with a better method?
NSString *newDec = [display text]; //takes user input from display
NSString *string = #"";
NSUInteger x = newDec;
int i = 0;
while (x > 0) {
string = [[NSString stringWithFormat:#"%u", x&1] stringByAppendingString:string];
x = x>> 1;
++i;
}
display.text = string; //Displays result in ios text box
Try this:
NSUInteger x = [newDec integerValue];
And next time don't ignore the Compiler's "Incompatible pointer to Integer conversion" hint...
Explanation: Afaik, assigning an object to an int, actually assigns the address of the object to that integer, not the content of the string (which is what you want).
Related
I am trying to convert a nsstring with hex values into a float value.
NSString *hexString = #"3f9d70a4";
The float value should be = 1.230.
Some ways I have tried to solve this are:
1.NSScanner
-(unsigned int)strfloatvalue:(NSString *)str
{
float outVal;
NSString *newStr = [NSString stringWithFormat:#"0x%#",str];
NSScanner* scanner = [NSScanner scannerWithString:newStr];
NSLog(#"string %#",newStr);
bool test = [scanner scanHexFloat:&outVal];
NSLog(#"scanner result %d = %a (or %f)",test,outVal,outVal);
return outVal;
}
results:
string 0x3f9d70a4
scanner result 1 = 0x1.fceb86p+29 (or 1067282624.000000)
2.casting pointers
NSNumber * xPtr = [NSNumber numberWithFloat:[(NSNumber *)#"3f9d70a4" floatValue]];
result:3.000000
What you have is not a "hexadecimal float", as is produced by the %a string format and scanned by scanHexFloat: but the hexadecimal representation of a 32-bit floating-point value - i.e. the actual bits.
To convert this back to a float in C requires messing with the type system - to give you access to the bytes that make up a floating-point value. You can do this with a union:
typedef union { float f; uint32_t i; } FloatInt;
This type is similar to a struct but the fields are overlaid on top of each other. You should understand that doing this kind of manipulation requires you understand the storage formats, are aware of endian order, etc. Do not do this lightly.
Now you have the above type you can scan a hexadecimal integer and interpret the resultant bytes as a floating-point number:
FloatInt fl;
NSScanner *scanner = [NSScanner scannerWithString:#"3f9d70a4"];
if([scanner scanHexInt:&fl.i]) // scan into the i field
{
NSLog(#"%x -> %f", fl.i, fl.f); // display the f field, interpreting the bytes of i as a float
}
else
{
// parse error
}
This works, but again consider carefully what you are doing.
HTH
I think a better solutions is a workaround like this :
-(float) getFloat:(NSInteger*)pIndex
{
NSInteger index = *pIndex;
NSData* data = [self subDataFromIndex:&index withLength:4];
*pIndex = index;
uint32_t hostData = CFSwapInt32BigToHost(*(const uint32_t *)[data bytes]);
return *(float *)(&hostData);;
}
Where your parameter is an NSData which rapresents the number in HEX format, and the input parameter is a pointer to the element of NSData.
So basically you are trying to make an NSString to C's float, there's an old fashion way to do that!
NSString* hexString = #"3f9d70a4";
const char* cHexString = [hexString UTF8String];
long l = strtol(cHexString, NULL, 16);
float f = *((float *) &l);
// f = 1.23
for more detail please see this answer
Please forgive the simplicity of the question. I'm completely new to Objective C.
I'd like to know how to concatenate integer and string values and print them to the console.
This is what I'd like for my output:
10 + 20 = 30
In Java I'd write this code to produce the needed results:
System.Out.Println(intVarWith10 + " + " + intVarWith20 + " = " + result);
Objective-C is quite different. How can we concatenate the 3 integers along with the strings in between?
You can use following code
int iFirst,iSecond;
iFirst=10;
iSecond=20;
NSLog(#"%#",[NSString stringWithFormat:#"%d + %d =%d",iFirst,iSecond,(iFirst+iSecond)]);
Take a look at NSString - it has a method stringWithFormat that does what you require. For example:
NSString* yString = [NSString stringWithFormat:#"%d + %d = %d",
intVarWith10, intVarWith20 , result];
You can use C style syntax, with NSLog (If you just need to print)
NSLog(#"%d+%d=%d",intvarWith10,intvarWith20,result);
If you want a string variable holding the value
NSString *str = [NSString stringWithFormat:#"%d+%d=%d",intvarWith10,intvarWith20,result];
You have to create an NSString with format and specify the data type.
Something like this :
NSInteger firstOperand=10;
NSInteger secondOperand=20;
NSInteger result=firstOperand+secondOperand;
NSString *operationString=[NSString stringWithFormat:#"%d + %d = %d",firstOperand,secondOperand,result];
NSLog(#"%#",operationString);
NSString with format follows the C printf syntax
Check below code :
int i = 8;
NSString * tempStr = [NSString stringWithFormat#"Hello %d",i];
NSLog(#"%#",tempStr);
I strongly recommend you this link Objective-C Reference.
The Objective-C int data type can store a positive or negative whole number. The actual size or range of integer that can be handled by the int data type is machine and compiler implementation dependent.
So you can store like this.
int a,b;
a= 10;
b= 10;
then performing operation you need to first understand NSString.
C style character strings are composed of single byte characters and therefore limited in the range of characters that can be stored.
int C = a + b;
NSString *strAnswer = [NSString stringWithFormat:#"Answer %d + %d = %d", a , b, c];
NSLog(#"%#",strAnswer)
Hope this will help you.
I am trying to add a positive/negative button onto a numerical input in a UItextfield, but I cannot get it to function properly. What I want it to do is just add or remove a negative sign from the front of the numerical input. I am able to do that, however I cannot find a method to maintain the original number of decimal places. This is what I have tried:
- (IBAction) negsign
{
float input = [userinput.text floatValue];
float result = ((input * (-1)));
negstring = [NSString stringWithFormat:
#"%f", result];
userinput.text = negstring;
}
With this I get just a string of zeros after, like -23.0000000. I've tried limiting the decimal places by changing to #"%.2f" but I dont want extra zeros for whole integers, or rounding more than 2 decimals places. I just want it to take something like 34.658939 or 23 and make it -34.658939 or -23. Does anyone have a method to do this?
What would work best in your case is the following code:
float input = [userinput.text floatValue];
float result = ((input * (-1)));
NSNumber *resultNum = [NSNumber numberWithFloat:result];
NSString *resultString = [resultObj stringValue];
userinput.text = resultString;
If you're trying to make the number negative instead of reversing the sign, it'd be better if you replace float result = ((input * (-1))); with float result = -ABS(input);
Really, the best way to handle this would be to never convert it from a string in the first place. Just replace the first character as needed like this:
- (IBAction) negsign
{
unichar firstCharacter = [userinput.text characterAtIndex:0];
if (firstCharacter == '-') {
// Change the first character to a + sign.
userinput.text = [userinput.text stringByReplacingCharactersInRange:NSMakeRange(0, 1)
withString:#"+"];
} else if (firstCharacter == '+') {
// Change the first character to a - sign.
userinput.text = [userinput.text stringByReplacingCharactersInRange:NSMakeRange(0, 1)
withString:#"-"];
} else {
// There is no sign so we assume that it is positive.
// Insert the - at the beginning.
userinput.text = [userinput.text stringByReplacingCharactersInRange:NSMakeRange(0, 0)
withString:#"-"];
}
}
I am trying to trim zeros after a decimal point as below but it's not giving desired result.
trig = [currentVal doubleValue];
trig = trig/100;
NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
[formatter setMaximumFractionDigits:0];
display.text = [formatter stringFromNumber:[NSNumber numberWithDouble:trig]];
The number is still being displayed without trimming zeros after the decimal point.
Here currentVal is the number I am entering.
For example if i pass "trig" = 123 (Initially "trig" = 123 after doing trig/100 i want to display 1.23 but it is displaying as 1.23000000).
Sometimes the straight C format specifiers do an easier job than the Cocoa formatter classes, and they can be used in the format string for the normal stringWithFormat: message to NSString.
If your requirement is to not show any trailing zeroes, then the "g" format specifier does the job:
float y = 1234.56789f;
NSString *s = [NSString stringWithFormat:#"%g", y];
Notice that there is no precision information, which means that the printf library will remove the trailing zeroes itself.
There is more information in the docs, which refer to IEEE's docs.
In case this helps someone. I wanted 1 decimal value but no '.0' on the end if the float was '1.0'. Using %g would give scientific notation for longer numbers, following ugliness worked well enough for me as high accuracy wasn't critical.
// Convert to 1 dp string,
NSString* dirtyString = [NSString stringWithFormat: #"%.1f", self.myFloat];
// Convert back to float that is now a maximum of 1 dp,
float myDirtyFloat = [dirtyString floatValue];
// Output the float subtracting the zeros the previous step attached
return [NSString stringWithFormat: #"%g", myDirtyFloat];
This will not display any decimal value after the decimal point:
display.text = [NSString stringWithFormat:#"%1.0f", trig];
This will just trim the zeros after the decimal point:
isplay.text = [NSString stringWithFormat:#"%3.2f", trig];
display.text = [display.text stringByTrimmingCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:[NSString stringWithFormat#"0"]]];
Note, this may leave you with the trailing decimal point. "124." may happen. I guess that some smarter solution will be posted soon.
From the documentation, it looks like setFractionDigits: is only for converting the other way.
The best thing to do is probably to convert your number to an integer before formatting it e.g.
double converted = round(trig); // man round for docs
You can use also the formatting functions of stringWithFormat: of NSString, but then you will lose all the localisation advantages you get with NSNumberFormatter.
This may not be a proper solution where there is NSNumberFormetter Class, But I just did this rather then googling a lot! ;)
Here is an example, if it helps:
-(NSString*) trimZerosAfterDecimalPoint:(NSString*)string_ {
double doubleValue=[string_ doubleValue];
long leftPart=(long)doubleValue;
double rightPart=doubleValue-(double)leftPart;
NSString *rightPartAsStr=[NSString stringWithFormat:#"%f", rightPart];
int i=0;
for (i=rightPartAsStr.length-1; i>=2; i--) {
if ([rightPartAsStr characterAtIndex:i]!='0') {
rightPartAsStr=[rightPartAsStr substringWithRange:NSMakeRange(2, i-1)];
break;
}
}
if (i<2) {
string_=[NSString stringWithFormat:#"%ld", leftPart];
} else {
string_=[NSString stringWithFormat:#"%ld.%#", leftPart, rightPartAsStr];
}
return string_;
}
I just had to do this for one of my programs and heres how I went about it:
- (void) simplify{
int length = (int)[self.calcString length];
for (int i = (int)[self.calcString length]; i > 0; i--) {
if ([self.calcString rangeOfString:#"."].location != NSNotFound) {
NSRange prevChar = NSMakeRange(i-1, 1);
if ([[self.calcString substringWithRange:prevChar] isEqualToString:#"0"]||
[[self.calcString substringWithRange:prevChar] isEqualToString:#"."])
length--;
else
break;
}
self.calcString = [self.calcString substringToIndex:length];
}
}
This works
display.text = [#(trig) stringValue];
it is because of your datatype cannot be formatted is such a manner.
I am trying to convert from an int to a string but I am having trouble. I followed the execution through the debugger and the string 'myT' gets the value of 'sum' but the 'if' statement does not work correctly if the 'sum' is 10,11,12. Should I not be using a primitive int type to store the number? Also, both methods I tried (see commented-out code) fail to follow the true path of the 'if' statement. Thanks!
int x = [my1 intValue];
int y = [my2 intValue];
int sum = x+y;
//myT = [NSString stringWithFormat:#"%d", sum];
myT = [[NSNumber numberWithInt:sum] stringValue];
if(myT==#"10" || myT==#"11" || myT==#"12")
action = #"numGreaterThanNine";
If you just need an int to a string as you suggest, I've found the easiest way is to do as below:
[NSString stringWithFormat:#"%d",numberYouAreTryingToConvert]
You can use literals, it's more compact.
NSString* myString = [#(17) stringValue];
(Boxes as a NSNumber and uses its stringValue method)
The commented out version is the more correct way to do this.
If you use the == operator on strings, you're comparing the strings' addresses (where they're allocated in memory) rather than the values of the strings. This is very occasional useful (it indicates you have the exact same string object), but 99% of the time you want to compare the values, which you do like so:
if([myT isEqualToString:#"10"] || [myT isEqualToString:#"11"] || [myT isEqualToString:#"12"])
== shouldn't be used to compare objects in your if. For NSString use isEqualToString: to compare them.
int val1 = [textBox1.text integerValue];
int val2 = [textBox2.text integerValue];
int resultValue = val1 * val2;
textBox3.text = [NSString stringWithFormat: #"%d", resultValue];
Simply convert int to NSString
use :
int x=10;
NSString *strX=[NSString stringWithFormat:#"%d",x];
Dot grammar maybe more swift!
#(intValueDemo).stringValue
for example
int intValueDemo = 1;
//or
NSInteger intValueDemo = 1;
//So you can use dot grammar
NSLog(#"%#",#(intValueDemo).stringValue);