Empty function interpretations

[Bart Bogaerts]

are not allowed.

for example ColorOf<cf> = {}

This is not handy if the interpretations are automaticcaly generated.

[Broes De Cat]

Fixes #246 Reading in an empty interpretation assumed the symbol was a predicate symbol. Now, it is also checked for functions.

→ <<cset e33445e31a47>>

[Broes De Cat]

Refs #246 Added a test on parsing an empty function interpretation.

→ <<cset 6a03956a6754>>

[Bart Bogaerts]

fixed parsing issue: parsing empty interpretations

see #246. This issue was previously fixed in commit e33445e31a47. However, the fix there was only valid for two-valued interpretations. I extended this to threevalued interpretations.

Also: added a test for this behaviour

→ <<cset 5baeb18f5bd1>>