Parameter type transformation

PowerShell allows us to ignore the idea of variable types in most situations and this is a tremendous productivity boost. When you consider all of the different Common Language Runtime (CLR) types that are used in a typical script it's easy to see why not worrying about naming the types saves a lot of time. Adding in all of the anonymous types (for instance, results of a select-object call), the need for a very liberal typing system is obvious. One example when specifying types is useful, or even critical, is when specifying parameters to a function:

function get-dayofweek{
param($date)
  Write-Output $date.DayOfWeek
}

This function seems like it would work well, but testing it shows that it's not quite right, as shown in the following screenshot:

Since we didn't specify what type the parameter was, the problem was that the constant string '5/27/2014' was passed into the parameter as is, that is, as a string. Since the string didn't have a DayOfWeek property, the...