Batch equivalent to: $(dirname ${0})/$(basename ${0} .<old_suffix>)<new_suffix>

Actually it is not PowerShell but useful in bat scripts starting PowerShell scripts.

%~dp0%~n0.ps1

If you want to use it in the previous post, you cannot put it in a variable first if the result contains space characters. For some obscure reason. Not connected with this fomula.