| sk = fs ', is_fskey(sk) ⊦ addclass(class1, fis1 + (sk × val0) ', st) = addclass(class1, fis1, st), fs .class = class1 |
⊦ addclass(class1, fis1 + (fs ' × val0) ', st) = addclass(class1, fis1, st), fs .class = class1
[[CONCRETESIMPRULES : ([CSIMPSEQ : ⊦ is_fskey(fs ')])]]