how to check if a double ends in .33

Question

I am writing in swift and I need to carry out code similar to this if myDouble ends in .33 { "carry out code"} How do I run a check on the decimal value of my number while ignoring the whole numbers? Thanks

Wouldn't you need to round it first? 1/3 wouldn't end in .33, it actually never ends theoretically.. — ergonaut, Oct 13 '15 at 00:25
this number is user defined from a text field so I need to add 0.01 to the number if they choose a number ending in .33 before I use the number in the rest of my calculations — ElectricTiger, Oct 13 '15 at 00:29
Yea, your basic logic is flawed... What if the double "ends" in .330000000001 are you saying you wouldn't want to run the code in question? Because frankly, a double will never end in *exactly* .33. The structure of a Double won't allow it. — Daniel T., Oct 13 '15 at 00:29
Either convert it to a string, separate it at the "." and examine the decimal string part. Or this may help if you don't want to use Strings: http://stackoverflow.com/questions/31396301/getting-the-decimal-part-of-a-double-in-swift — myles, Oct 13 '15 at 00:32
Do something like: `if fabs(fabs(myDouble) - floor(fabs(myDouble)) - 0.33) < 0.001`. Adjust `0.001` to whatever accuracy you are looking for. — vacawama, Oct 13 '15 at 00:45

score 2 · Accepted Answer · answered Oct 13 '15 at 00:53

2

let myDouble = 10.0/3  //  3.333333333333333

if String(format: "%.2f", myDouble).hasSuffix(".33") {
    print(true)
}

answered Oct 13 '15 at 00:53

Leo Dabus

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Thank you. This worked perfectly. Short sharp and affective. Exactly what I was hoping to use – ElectricTiger Oct 13 '15 at 21:24

score 0 · Answer 2 · edited Oct 13 '15 at 00:46

0

Just do abs(myDouble - floor(myDouble)), that will get your decimal value. then do any rounding or formatting needed to handle infinite 3's or what not

Make sure you import Foundation, it's required to use floor: import Foundation

edited Oct 13 '15 at 00:46

Charles Truluck

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answered Oct 13 '15 at 00:34

Knight0fDragon

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score 0 · Answer 3 · answered Oct 13 '15 at 00:43

0

let double = 4.3391762
let newDouble = String(format: "%.03f", double)
let thirtyThree = abs(Double(newDouble)! - floor(Double(double))) * 100

floor(thirtyThree)

Probably could be refactored but there's one way.

answered Oct 13 '15 at 00:43

Aaron

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how to check if a double ends in .33

3 Answers3