Question

I am seeing some rather weird behavior with PowerShell, it looks like custom functions might need a ‘parenthesis wrapper’ to evaluate as you might expect them. Given a simple PowerShell function:

function Return-True { return $true } 

and then some sample code to invoke it:

PS C:\> Return-True True PS C:\> Return-True -eq $false True PS C:\> (Return-True) -eq $false False 

Ideas? Comments?

Answer 1

When PowerShell sees the token Return-True it identifies it as a command and until evaluation or end of the statement, everything else is an argument which is passed to the function Return-True.

You can see this in action if you do:

PS > function Return-True { 'The arguments are: $args'; return $true } PS > Return-True -eq $false The arguments are: -eq False True 

That’s why all of the following return ‘True’, because all you are seeing is the result of calling Return-True with various arguments:

PS > Return-True -eq $false True PS > Return-True -ne $false True PS > Return-True -eq $true True PS > Return-True -ne $true True 

Using (Return-True) forces PowerShell to evaluate the function (with no arguments).