Re. SIMPLE-STRING: hard to say for sure without benchmarking, really.
Oftentimes having both (SIMPLE-ARRAY CHARACTER (*)) and (SIMPLE-ARRAY BASE-CHAR (*)) in their own legs is worth it -- but I'm not really sure if MAP-INTO sees that much use with strings in the first place.
Re. SIMPLE-STRING: hard to say for sure without benchmarking, really.
Oftentimes having both (SIMPLE-ARRAY CHARACTER (*)) and (SIMPLE-ARRAY BASE-CHAR (*)) in their own legs is worth it -- but I'm not really sure if MAP-INTO sees that much use with strings in the first place.