let step k st outs ins =
if st <> T.OO then k st outs ins else
match ins with
+ | "CONCATENATION" :: tl -> k T.OK ("CONCATENATION" :: outs) tl
+ | "APPEND" :: tl -> k T.OK ("CONCATENATION" :: outs) tl
| "LENGTH" :: tl -> k T.OK ("LENGTH" :: outs) tl
| "ITERATED" :: "TAIL" :: tl -> k T.OK ("TAIL" :: "ITERATED" :: outs) tl
+ | "TAIL" :: tl -> k T.OK ("TAIL" :: outs) tl
| "HEAD" :: "AND" :: "TAIL" :: tl -> k T.OK ("TAIL" :: "AND" :: "HEAD" :: outs) tl
| "NAT-LABELED" :: "REFLEXIVE" :: "AND" :: "TRANSITIVE" :: "CLOSURE" :: tl -> k T.OK ("CLOSURE" :: "TRANSITIVE" :: "AND" :: "REFLEXIVE" :: "NAT-LABELED" :: outs) tl
| "LABELLED" :: "TRANSITIVE" :: "CLOSURE" :: tl -> k T.OK ("CLOSURE" :: "TRANSITIVE" :: "LABELLED" :: outs) tl