This question already has answers here:
Difference between decimal, float and double in .NET?
(18 answers)
Closed 9 years ago.
I have a strange issue using double numbers in C# . NET here is my test:
double my_value = 0.49;
the problem is that the variable value shown is instead 0.48999999999999999 I do not need to display 0.49 using Math.Round() function; I need to exactly store this value.
Thank you.
Welcome to floating point precision. Use the decimal type if you want more precision.
decimal my_value = 0.49m;
If you want to learn more on why this is I recommend you read this article - What Every Computer Scientist Should Know About Floating-Point Arithmetic
Use decimal instead, double is floating binary point type.
decimal my_value = 0.49m;
Useful links;
Floating-Point Representation and Precision
What Every Computer Scientist Should Know About Floating-Point Arithmetic
Do not use the double type when you need to use exact values. That is the domain of the decimal type
decimal my_value = 0.49m;
Related
This question already has answers here:
Is floating point math broken?
(31 answers)
Closed 4 months ago.
I have a problem with conversation of double values.
In the picture Project's framework is .NET6 and i tried on .NET5 and i get same value again on x64.
Can you explain this situation to me?
And how can I get the value unchanged on x64?
Thank you.
This is expected behavior: floating point numbers have a limited number of significant digits, and a number that has a finite number of digits in their decimal representation may require infinite digits in their binary representation.
E.g., the decimal 0.1 is, in binary, 0.00011001100110011.... repeating. Storing this in a float or double, the number of digits is truncated.
Floating point numbers behave similar, but not identical to "real" numbers. This is something you should be aware of.
For financial mathematics, in C#, use the decimal type.
Here you find a good "what every developer should know" overview: https://floating-point-gui.de/.
The standard governing the most common (almost ubiquitous) implementation of floating point types is IEEE 754.
This question already has answers here:
Why is floating point arithmetic in C# imprecise?
(3 answers)
decimal vs double! - Which one should I use and when? [duplicate]
(7 answers)
Closed 6 years ago.
double sth = 250 - 249.99;
Console.WriteLine(sth);
Why does this return sth like 0.009994507, instead of 0.01?
Floating point numbers (in this case doubles) cannot represent decimal values exactly. For more info, see this page here
If you need a more accurate representation, use decimal instead.
because when you print the double you print the all double value not just the first x after point digits.
you can use String.Format to print only the first 2 numbers.
double sth = 250.00d - 249.99d;
string sthString = String.Format("{0:0.00}", sth);
Console.WriteLine(sthString);
There are a lot of decimals that have infinite binary representation. What you're experiencing is exactly this case.
For more on this topic see: http://www.exploringbinary.com/why-0-point-1-does-not-exist-in-floating-point/
This question already has answers here:
Is floating point math broken?
(31 answers)
Closed 7 years ago.
AFAIK .NET's default round option is to even, so Math.Round(1.225,2) should give 1.22 but it gives 1.23.
Math.Round(2.225,2) = 2.22
Math.Round(100.225,2) = 100.22
all the values I tried rounds to nearest even but only 1.225 and -1.225 rounds to 1.23 and -1.23.
The main problem is that in float and double, the amount of decimal places is not part of the value, and the precision isn't decimal, but rather, binary. And there's no finite binary number that can represent 1.225 exactly.
So when you do Math.Round(1.225f, 2), you're actually doing something more like Math.Round(1.22500002f, 2) - there's no midpoint rounding involved.
The same problem appears with Math.Round(2.225f, 2) - it's just that the "real" value is slightly smaller than 2.225f, so the result rounds down. But there's still no midpoint rounding involved.
If you need decimal precision, use decimal. Neither float nor double are designed for decimal precision - they're fine for e.g. physics calculations, but not for e.g. accounting.
1.225 can't be represented exactly in floating point, so you're really rounding 1.225000023841858.
This question already has answers here:
Double vs Decimal Rounding in C#
(2 answers)
Closed 7 years ago.
I am doing following equation but the result is not as expected
double dasdas = Math.Abs(3.2 - 1.9);
The result is
1.3000000000000003
However the correct result should be
1.3
What may be the reason of this?
c# 4.5.2
This is because you're using a double - which is a floating point. These by definition this cannot store the exact number.
You need to use Decimal.
Take at look at here and What Every Computer Scientist Should Read About Floating Point
Use decimal:
decimal dasdas = Math.Abs(3.2m - 1.9m);
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Parse a Number from Exponential Notation
Does Decimal.Parse() support scientific notation?
I am trying to convert such values as 1E-08 to a decimal in C# because decimals are the preffered datatype for handling funds yet I get an error upon decimal.Parse() "Input string was not in a correct format." wouldn't converting to float first and then to decimal defeat the purpose?
Yes, converting to float would indeed defeat the purpose. The good thing is, you don't have to do that here!
You can use an overload for Parse that takes a NumberStyles specifier:
decimal d = decimal.Parse("1E-08",
System.Globalization.NumberStyles.AllowExponent);
Of course, if you are merely specifying a hard-coded decimal, you can use the decimal literal format:
decimal d = 1E-08M;
You can try with :-
decimal x = decimal.Parse("1E-08", NumberStyles.Float);