<PRIVATE
: subseq-range ( seq subseq -- from/f to/f )
- [ find-subseq ] keep '[ dup _ length + ] [ f f ] if* ; inline
+ [ subsequence-starts ] keep '[ dup _ length + ] [ f f ] if* ; inline
: (split1) ( seq subseq snip-quot -- before after )
[ [ subseq-range ] keepd over ] dip [ 2nip f ] if ; inline