PowerShell syntax for complex literals (array, hash), custom objects and calculated properties

literals.ps1

# Hash table syntax is @{ name = value; name = value; ... } -- Curly braces and semicolons

$map = @{ key1 = "value1"; key2 = 3.14 }
echo $map.key1      # "value1"
echo $map["key2"]   # 3.14

# Coerce it to a new object
[PSCustomObject] $map

# Btw, you can SELECT a "calculated property" (or synthetic property, if that's how your brain works):
ls | sel -fir 3 | sel Name,LastWriteTime,@{Name="NooProperty";Expr={ $_.LastWriteTime.AddDays(-90) }}

# Array (list) syntax is @( value, value, ...) -- Parens, commas.  
# Type declaration is "[type[]]", where "type" is the type of your array elements.

$list = @( 3.14, "value2" )
echo $list[0]   # 3.14
echo $list[1]   # "value2"

# If you want to BUILD a list:
# (From https://stackoverflow.com/a/33156229/370611)

$outItems = New-Object Collections.Generic.List[Object] # Or, say, Int64 or Int32 or String or whatever
$outItems.Add(1)
$outItems.Add("hi")
$outItems.ToArray()