| ⊦ flatten(val ++ stringval(`')) = val ++ stringval(`'), is_valuelist(val) |
⊦ ¬ is_valuelist(val0) → flatten(val ++ val0) = flatten(val) ++ val0
⊦ ¬ is_valuelist(val) → flatten(val) = val
[[CONCRETESIMPRULES : ([CSIMPSEQ : ⊦ ¬ is_valuelist (stringval(stringvar))], [CSIMPSEQ : ⊦ val ++ val1 = val0 ++ val1 ↔ val = val0])], [EXTRAFMAS : (is_valuelist(stringval(`')))]]