Why am I getting 0 when subtracting 5.0 from 650.50 using the subtracting() method?
in the following code, adding, multiplying and dividing work fine, but why subtracting doesn't? What am I doing wrong?
See code in IBM's sandbox: http://swift.sandbox.bluemix.net/#/repl/59b1387696a0602d6cb19201
import Foundation
let num1:NSDecimalNumber = 650.50
let num2:NSDecimalNumber = 5.0
let result = num1.adding(num2)
let result2 = num1.subtracting(num2)
let result3 = num1.multiplying(by: num2)
let result4 = num1.dividing(by: num2)
print("Addition: \(result)") // Addition: 655.5
// Why am I getting 0 here and not 645.5?
print("Subtraction: \(result2)") //Subtraction: 0
print("Multiplication: \(result3)") //Multiplication: 3252.5
print("Division: \(result4)") //Division: 130.1
Apples Docs: https://developer.apple.com/documentation/foundation/nsdecimalnumber
This may be because of a specificity of the IBM sandbox related to NSDecimalNumber (indeed many parts of Foundation are still not entirely available on Linux).
Anyway, whatever the bug is, a solution is to use the Swift counterpart to NSDecimalNumber which is Decimal.
Despite the fact that this is supposed to be only a wrapper around NSDecimalNumber, it gives the correct result, even on the IBM platform.
Note that this wrapper doesn't use the NSDecimalNumber methods, it uses Swift operators such as + or *.
import Foundation
let num1: Decimal = 650.50
let num2: Decimal = 5.0
let result = num1 + num2
let result2 = num1 - num2
let result3 = num1 * num2
let result4 = num1 / num2
print("Addition: \(result)")
print("Subtraction: \(result2)")
print("Multiplication: \(result3)")
print("Division: \(result4)")
Gives:
Addition: 655.5
Subtraction: 645.5
Multiplication: 3252.5
Division: 130.1