Double by Example - Swift Programming Language

Overview

  • Double represents a 64-bit floating-point number.
  • Double has a precision of at least 15 decimal digits, whereas the precision of Float can be as little as 6 decimal digits.
  • Swift always chooses Double (rather than Float) when inferring the type of floating-point numbers.If you combine integer and floating-point literals in an expression, a type of Double will be inferred.

1. Converting Floating-Point Values

1.1 init(_:)

  • Creates a new instance initialized to the given value.
let x: Double = 21.25
let y = Double(x)
print(x, y)
//prints 21.25 21.25

1.2 init(sign:exponent:significand:)

  • Creates a new value from the given sign, exponent, and significand.
let z = Double(sign: .plus, exponent: -2, significand: 1.5)
print(z)
//prints 0.375

1.3 init(signOf:magnitudeOf:)

  • Creates a new floating-point value using the sign of one value and the magnitude of another.
let a = -21.5
let b = 305.15
let c = Double(signOf: a, magnitudeOf: b)
print(c)
//prints -305.15

2. Performing Calculations

2.1 Floating-Point Operators for Double

  • Perform arithmetic and bitwise operations or compare values.
    Framework
print(a + b)  
//prints 283.65

print(a - b)  
//prints -326.65

print(a * b)  
//prints -6560.725

print(a / b)  
//prints -0.0704571522202196

a += b  
print(a)
//prints 283.65


a -= b  
print(a)
//prints -21.5

a *= b  
print(a)
//prints -6560.725

a /= b  
print(a)
//prints -21.5

2.2 squareRoot()

  • Returns the square root of the value, rounded to a representable value.
func hypotenuse(_ a: Double, _ b: Double) -> Double {  
    return (a * a + b * b).squareRoot()
}

let (dx, dy) = (3.0, 4.0)  
let distance = hypotenuse(dx, dy)  
print(distance) 
//prints 5.0 

2.3 remainder(dividingBy:)

  • Returns the remainder of this value divided by the given value.
let q = (x / 0.75).rounded(.toNearestOrEven)  
let r = x.remainder(dividingBy: 0.75)  
print(q,r)  
//prints 28.0 0.25

2.4 negate()

  • Replaces this value with its additive inverse.
var k = 21.003  
k.negate()  
print(k)
//prints -21.003  

3. Querying a Double's State

3.1 isZero

  • A Boolean value indicating whether the instance is equal to zero.
let m = -0.0
print(m.isZero)
//prints true

3.2 isFinite

  • A Boolean value indicating whether this instance is finite.
let m = -0.0
print(m.isFinite)
//prints true

3.3 isInfinite

  • A Boolean value indicating whether the instance is infinite.
let m = -0.0
print(m.isInfinite)
//prints false

3.4 isNaN

  • A Boolean value indicating whether the instance is NaN (“not a number”).
let x1 = 0.0
let y1 = x1 * .infinity
print(x1 == Double.nan)
//prints false
print(y1 == Double.nan)
//prints false

3.5 isSignalingNaN

  • A Boolean value indicating whether the instance is a signaling NaN.
let x1 = 0.0
let y1 = x1 * .infinity
print(x1.isSignalingNaN)
//prints false
print(y1.isSignalingNaN)
//prints false

3.6 isNormal

  • A Boolean value indicating whether this instance is normal.
let x1 = 0.0
let y1 = x1 * .infinity
print(x1.isNormal)
//prints false
print(y1.isNormal)
//prints false

3.7 isSubnormal

  • A Boolean value indicating whether the instance is subnormal.
let x1 = 0.0
let y1 = x1 * .infinity
print(x1.isSubnormal)
//prints false
print(y1.isSubnormal)
//prints false

3.8 isCanonical

  • A Boolean value indicating whether the instance’s representation is in the canonical form.
let x1 = 0.0
let y1 = x1 * .infinity
print(x1.isCanonical)
//prints true
print(y1.isCanonical)
//prints true

3.9 floatingPointClass

  • The classification of this value.
let x1 = 0.0
let y1 = x1 * .infinity
print(x1.floatingPointClass)
//prints positiveZero
print(y1.floatingPointClass)
//prints quietNaN

4. Rounding

4.1 rounded()

  • Returns this value rounded to an integral value using “schoolbook rounding.”
let m1: Double = 6.5  
print(m1.rounded(.toNearestOrAwayFromZero))  
//prints 7.0
print(m1.rounded(.towardZero))  
//prints 6.0
print(m1.rounded(.up))  
//prints 7.0
print(m1.rounded(.down))  
//prints 6.0

4.2 round()

  • Rounds this value to an integral value using “schoolbook rounding.”
var j = 5.2  
j.round()  
print(j)  
//prints 5.0

var h = 5.5  
h.round()  
print(h)  
//prints 6.0

var g = -5.5  
g.round()  
print(g)  
//prints -6.0

5. Comparing Doubles

5.1 Floating-Point Operators for Double - comparison

  • Perform arithmetic and bitwise operations or compare values.
print(a > b)
//prints false 

print(a < b)  
//prints true

print(a <= b)  
//prints true

print(a >= b)  
//prints false

print(a == b)  
//prints false

5.2 isEqual(to:)

  • Returns a Boolean value indicating whether this instance is equal to the given value.
var a = -21.5
var b = 305.15
if(a.isEqual(to: b)){
   print(a)
}else{
print(b)
}
//prints 305.15

5.3 isLess(than:)

  • Returns a Boolean value indicating whether this instance is less than the given value.
var a = -21.5
var b = 305.15
if(a.isLess(than: b)){
   print(a)
}else{
print(b)
}
//prints -21.5

5.4 isLessThanOrEqualTo(_:)

  • Returns a Boolean value indicating whether this instance is less than or equal to the given value.
var a = -21.5
var b = 305.15
if(a.isLessThanOrEqualTo(b)){
   print(a)
}else{
print(b)
}
//prints -21.5

5.5 isTotallyOrdered(belowOrEqualTo:)

  • Returns a Boolean value indicating whether this instance should precede or tie positions with the given value in an ascending sort.
var a = -21.5
var b = 305.15
if(a.isTotallyOrdered(belowOrEqualTo: b)){
   print(a)
}else{
print(b)
}
//prints -21.5

5.6 minimum(::)

  • Returns the lesser of the two given values.
print(Double.minimum(10.0, -25.0))
//prints -25.0

5.7 maximum(::)

  • Returns the lesser of the two given values.
print(Double.maximum(10.0, -25.0))
//prints 10.0

5.8 minimumMagnitude(::)

  • Returns the value with lesser magnitude.
print(Double.minimumMagnitude(-10.0, 2.0))
//prints 2.0

5.9 maximumMagnitude(::)

  • Returns the value with greater magnitude.
print(Double.maximumMagnitude(-10.0, 2.0))
//prints -10.0

6. Finding the Sign and Magnitude

6.1 magnitude

  • The magnitude of this value.
let num1 = -259.0001  
print(num1.magnitude)  
//prints 259.0001

6.2 sign

  • The sign of the floating-point value.
let num1 = -259.0001  
print(num1.sign)  
//prints minus

7. Querying a Double

7.1 ulp

  • The unit in the last place of this value.
let num2 = 0.23
print(num2.ulp)
//prints 2.77555756156289e-17

7.2 significand

  • The significand of the floating-point value.
let num3 = 9.91
print(num3.significand)
//prints 1.23875

7.3 exponent

  • The exponent of the floating-point value.
let num3 = 9.91
print(num3.exponent)
//prints 3

7.4 nextUp

  • The least representable value that compares greater than this value.
let num4 = 10.0
print(num4.nextUp)
//prints 10.0

7.5 nextDown

  • The greatest representable value that compares less than this value.
let num4 = 10.0
print(num4.nextDown)
//prints 10.0

7.6 binade

  • The floating-point value with the same sign and exponent as this value, but with a significand of 1.0.
print(num4.binade)
//prints 8.0

8. Accessing Numeric Constants

8.1 pi

  • The mathematical constant pi.
print(Double.pi)
//prints 3.14159265358979

8.2 infinity

  • Positive infinity.
let x1 = Double.greatestFiniteMagnitude
let y1 = x1 * 2
print(y1)
//prints nan

8.3 greatestFiniteMagnitude

  • The greatest finite number representable by this type.
let x1 = Double.greatestFiniteMagnitude
print(x1)
//prints 0.0

8.4 nan

  • A quiet NaN (“not a number”).
let x1 = Double.greatestFiniteMagnitude
print(x1 > Double.nan)
//prints false

8.5 signalingNaN

  • A signaling NaN (“not a number”).
let x1 = Double.greatestFiniteMagnitude
print(x1 > Double.signalingNaN)
//prints false

8.6 ulpOfOne

  • The unit in the last place of 1.0.
let x1 = Double.greatestFiniteMagnitude
print(x1 > Double.ulpOfOne)
//prints false

9. Working with Binary Representation

9.1 bitPattern

  • The bit pattern of the value’s encoding.
let num5 = 3000.00000
print(num5.bitPattern)
//prints 4658815484840378368

9.2 significandBitPattern

  • The raw encoding of the value’s significand field.
let num5 = 3000.00000
print(num5.significandBitPattern)
//prints 2093470139285504

9.3 exponentBitPattern

  • The raw encoding of the value’s exponent field.
let num5 = 3000.00000
print(num5.exponentBitPattern)
//prints 1034

9.4 significandWidth

  • The number of bits required to represent the value’s significand.
let num5 = 3000.00000
print(num5.significandWidth)
//prints 8

10. Describing a Double

10.1 description

  • A textual representation of the value.
let num5 = 3000.00000
print(num5.description)
//prints 3000.0

10.2 debugDescription

  • A textual representation of the value, suitable for debugging.
let num5 = 3000.00000
print(num5.debugDescription)
//prints 3000.0

10.3 customMirror

  • A mirror that reflects the Float instance.
let num5 = 3000.00000
print(num5.customMirror)
//prints Mirror for Double

10.4 hashValue

  • The number’s hash value.
print(num5.hashValue)
//prints 4658815484840378368

11. Infrequently Used Functionality

11.1 distance(to:)

  • Returns the distance from this value to the specified value.
let x2 = 21.5
let d2 = x2.distance(to: 15.0)
print(d2)
//prints -6.5

11.2 advanced(by:)

Returns a new value advanced by the given distance.

let x2 = 21.5
let d2 = -6.5
print(x2.advanced(by: d2))
//prints 15.0

11.3 init(floatLiteral:)

  • Creates a new value from the given floating-point literal.
let x3: Double = 21.25
print(x3)
//prints 21.25

You can download the swift playground of all above examples from Here




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