double

问题 I have the number 654987. Its an ID in a database. I want to convert it to a string. The regular Double.ToString(value) makes it into scientific form, 6.54987E5. Something I dont want. Other formatting functions Ive found checks the current locale and adds appropriate thousand separators and such. Since its an ID, I cant accept any formatting at all. How to do it? [Edit] To clarify: Im working on a special database that treats all numeric columns as doubles. Double is the only (numeric) type

问题 In Swift, how can one check if a string is a valid double value? I have been using the following extension from this question (but as a float) but if the value cannot be converted, it simply returns "0": extension String { var doubleValue:Double? { return (self as NSString).doubleValue } } Ideally, I would like it to return nil so it can be caught in an if-let , like so: if let i = str.doubleValue { object.price = i } else { // Tell user the value is invalid } 回答1: It is indeed more efficient

问题 My coworker did this experiment: public class DoubleDemo { public static void main(String[] args) { double a = 1.435; double b = 1.43; double c = a - b; System.out.println(c); } } For this first-grade operation I expected this output: 0.005 But unexpectedly the output was: 0.0050000000000001155 Why does double fails in such a simple operation? And if double is not the datatype for this work, what should I use? 回答1: double is internally stored as a fraction in binary -- like 1/4 + 1/8 + 1/16 +

问题 I am creating for fun, but I still want to approach it seriously, a site which hosts various tests. With these tests I hope to collect statistical data. Some of the data will include the percentage of the completeness of the tests as they are timed. I can easily compute the percentage of the tests but I would like true data to be returned as I store the various different values concerning the tests on completion. Most of the values are, in PHP floats, so my question is, if I want true

问题 This question is unlikely to help any future visitors; it is only relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation that is not generally applicable to the worldwide audience of the internet. For help making this question more broadly applicable, visit the help center. Closed 7 years ago . I think there's a lot for me to learn about data types. Why this happens double result = ((3/8)*100).ToString(); it gives zero .. should be 37,5 ... :(

问题 I need to print doubles so that definite number of symbols (like 8) is allocated for string representation of value. Next words should start at same index from beginning of string in each string. Now I have: value: 0 test value: 0.3333333333333 test value: 0.5 test I need: value: 0 test value: 0.33333333 test value: 0.5 test Test code: double[] ar = new double[] { 0, (double)1 / 3, (double)1 / 2 }; string s = "test"; foreach (var d in ar) { Console.WriteLine($"value: {d} {s}"); } What should

问题 Why does: double dividend = 1.0; double divisor = 3.0; Console.WriteLine(dividend / divisor * divisor); output 1.0, but: decimal dividend = 1; decimal divisor = 3; Console.WriteLine(dividend / divisor * divisor); outputs 0.9999999999999999999999999999 ? I understand that 1/3 can't be computed exactly, so there must be some rounding. But why does Double round the answer to 1.0, but Decimal does not? Also, why does double compute 1.0/3.0 to be 0.33333333333333331? If rounding is used, then

问题 In C#. I have a double (which I've extracted from a database) that has 20 digit precision. In Visual Studio (using QuickWatch) I can see the value of the double to be = 0.00034101243963859839. I want to display this value in a textbox and then have it be the same value when I take it out and convert it back into a double. But I always lose the last two digits I've tried the following: double d = 0.00034101243963859839; string s = d.ToString(); string s2 = d.ToString("F20"); string s3 = d

问题 In our code we have a double that we need to convert to an int. double score = 8.6; int i1 = Convert.ToInt32(score); int i2 = (int)score; Can anyone explain me why i1 != i2 ? The result that I get is that: i1 = 9 and i2 = 8 . 回答1: Because Convert.ToInt32 rounds: Return Value: rounded to the nearest 32-bit signed integer. If value is halfway between two whole numbers, the even number is returned; that is, 4.5 is converted to 4, and 5.5 is converted to 6. ...while the cast truncates: When you