Swift - Floating-Point Operations

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Introduction

When you add an integer constant to a Double, the resultant type would also be a Double type.

When you add an integer constant to a Float , the resultant type would also be a Float type. 

var sum1 = 5 + num1   //num1 and sum1 are both Double
var sum2 = 5 + num2   //num2 and sum2 are both Float

However, if you try to add Int and Double variables, you will get an error: 

var i4: Int = 123
var f1: Double = 3.14567
var r = i4 + f1          //error

To add two variables of different types, you need to cast the Int variable to Double : 

var r = Double (i4) + f1

When adding an integer to a floating-point number, the result would be a Double value. For example: 

var someNumber = 5 + 3.14

Here, someNumber would be inferred to be a Double.

In Swift, there is no implicit type conversion-you must explicitly convert an to a Float or Double: 

var f:Float
var i:Int = 5
f = i  //error
f = Float (i)

When casting a floating-point value to an integer, the value is always truncated:you will lose its fractional part: 

var floatNum = 3.5
var intNum = Int(floatNum)  //intNum is now 3

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