Koans/Introduction/AboutNumbers.Koans.ps1
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using module PSKoans [Koan(Position = 103)] param() <# Numbers In PowerShell, we can use several different data types to represent numbers. Which type is used depends on what you need. The two most common types are: - Integers Integers represent whole numbers. This is the default numeric data type that PowerShell uses for numbers that don't include a decimal portion. - Doubles Doubles are typically numbers which include decimal places or exponents. This is the default numeric type that PowerShell will use for numbers specified with decimal places or exponents, for example: - 0.5 - 2e3 So 10 will be an integer and 10.0 will be a double, unless a specific type is applied either with a type suffix or a cast, which will be covered in more detail in a later topic. The examples below display some of the differences inherent to the numeric types. #> Describe 'Basic Number Types' { Context 'Double' { It 'can result from an operation involving multiple types of numbers' { <# When doing arithmetic on different types of numbers, PowerShell will automatically convert the less precise or more narrow type to the other kind. #> $Int = 10 $Double = 10.0 'System.____' | Should -Be $Int.GetType().Fullname 'System.____' | Should -Be $Double.GetType().Fullname $Result = $Int * $Double # What type results when you multiply integers and doubles? 'System.____' | Should -Be $Result.GetType().Fullname } } Context 'Integers' { It 'has to be a whole number' { function Get-Number { param( [Parameter(Mandatory)] [int] $Number ) $Number } $Pi = [Math]::PI 'System.____' | Should -be $Pi.GetType().Fullname # What number will return if you pass Pi into an int function? ___ | Should -Be (Get-Number -Number $Pi) } It 'can be a larger number if needed' { <# Integers come in two flavours: - int (Int32) - long (Int64) If an integer value exceeds the limits of the Int32 type, it is automatically expanded to the larger Int64 type. #> # What exactly are the limitations of the [int] type? $MaxValue = [int]::MaxValue $MinValue = [int]::MinValue __ | Should -Be $MaxValue __ | Should -Be $MinValue # If you enter a number larger than that, the type should change. $BigValue = __ $BigValue | Should -BeOfType [long] $BigValue | Should -BeGreaterThan $MaxValue $SmallValue = __ $SmallValue | Should -BeOfType [long] $SmallValue | Should -BeLessThan $MinValue } It 'allows you to request the larger type with a suffix' { <# By specifying the L suffix, a number is forced to use the long type. here are more suffixes available, depending on your PowerShell version. We'll cover those in a later topic. #> 100L | Should -BeOfType [long] $Value = __ $Value | Should -BeOfType [long] [int]::MinValue -le $Value -and $Value -le [int]::MaxValue | Should -BeTrue } } } Describe "Banker's Rounding" { <# The default midpoint rounding method used in PowerShell is called "Rounding to Even," or "Banker's Rounding". Numbers will be rounded to the nearest even integer when rounding from a midpoint (###.5) value. This behaviour stems from the underlying library method [math]::Round() which is documented in more detail here: https://docs.microsoft.com/en-us/dotnet/api/system.math.round#midpoint-values-and-rounding-conventions Alternate overloads of the Round() method are also available if you need to adjust the midpoint rounding method used for a particular use case. #> It 'rounds to the nearest even when cast to integer if it is a midpoint' { # How will these numbers be rounded to integer? ____ | Should -Be ([int]2.5) ____ | Should -Be ([int]3.34) ____ | Should -Be ([int]12.7) ____ | Should -Be ([long]10.61) ____ | Should -Be ([long]5.5) } } |