sets: make sure that they work for sets (plus some simplification)

Signed-off-by: Peter Williams <pwil3058@gmail.com>
sets: be explicit about workarounds caused by opCmp signature problem

Signed-off-by: Peter Williams <pwil3058@gmail.com>
grammar: implement the class FIRST() function

Signed-off-by: Peter Williams <pwil3058@gmail.com>