What are the differences between storing numbers as Double and Decimal in terms of precision and usage?

Double and Decimal are two different formats for storing floating-point numbers, differing in precision and application scope.

• Double is a double-precision floating-point type (64-bit), based on the IEEE 754 standard. It stores numbers in binary format, which can lead to rounding errors when working with decimal fractions. Double is suitable for scientific calculations, graphics, where speed and a wide range are important, but absolute precision is not critical.

• Decimal is a fixed-precision decimal type that stores numbers in decimal format. It provides high accuracy and precise representation of decimal fractions, which is important for financial and accounting applications where rounding errors are unacceptable.

Example:

let doubleValue: Double = 0.1 + 0.2
print(doubleValue) // May output 0.30000000000000004

import Foundation
let decimalValue1 = Decimal(string: "0.1")!
let decimalValue2 = Decimal(string: "0.2")!
let decimalSum = decimalValue1 + decimalValue2
print(decimalSum) // Will output 0.3 exactly

In summary, choose Double for performance and a wide range, Decimal for precise financial calculations.