Peekee wrote:
>I am happy unless it rains.
>
>does this mean it is impossible for me to be happy when it is raining?
Another example to ponder:
Murphy CANNOT spend blue VCs UNLESS e is holding a strawberry.
Would that mean that e CAN spend blue VCs in all cases if e is holding
a strawberry? Even if e has no other VCs to spend with eir blue VC?
I also note the usage of "unless" in the present MMI:
4. CAN X ONLY IF Y: Equivalent to "CANNOT X unless Y".
This generalises to
<x> ONLY IF <y> == <not-x> unless <y>
The usual logical meaning of "only if" is an argument-reversed "if", thus
<x> ONLY IF <y> == <y> IF <x> == <not-x> IF <not-y>
which certainly looks like "unless" means "if not" rather than "iff not".
-zefram
