Option -e does not work if no file is provided

[Bart Bogaerts]

idp -e "stdoptions.xsb=true"

results in IDP listening to stdin

while

idp -i

DOES work without providing any files...

[Bart Bogaerts]

Related: you cannot pipe to an interactive IDP I would expect a behaviour where you CAN pipe to idp -i and it acts as if everything piped was in a file (i.e.~the main procedure is not executed)

Instead, piping to an interactive idp results in executing everything piped as lua code...

[Broes De Cat]

Reason for invalid: This is the expected behavior. After some thinking, any other behavior would result in more unintuitive behavior. 1) allowing piping with -i by default would be problematic when running idp -i without pipe nor files, which is quite useful. Note that idp -i -I can be used for this! 2) without -i, the system listens to pipes by default if no files are provided. Disabling this would make it less intuitive.