;;;; ELT

vector vs list x safe vs unsafe.

When safe, we must test that 0 <= index < (length seq).  Neither NTH nor
AREF does the right thing.



;;;; SUBSEQ

For lists have a fast and a safe version.

For vectors, convert into:
	(replace (make-array (- end start) :element-type ...)
		 sequence :start2 start :end2 end)


;;;; COPY-SEQ

Convert into (subseq seq 0).


;;;; LENGTH

Already delt with.


;;;; REVERSE and NREVERSE

For lists, just do it.

For vectors, have a speed>size transform and pre-compiled functions for:
	simple-vector
	(simple-array * (*))
	vector


;;;; MAKE-SEQUENCE

If the type is constant, try to convert into something else.



;;;; CONCATENATE

For list results, iterrate over all the sequences collecting the results.

For vector results, convert into a make-array followed by lots of replaces.



;;;; MAP

For list results, iterrate collecting the results.

For vector results,


;;;; MAP-INTO


;;;; SOME, EVERY, NOTANY, NOTEVERY


;;;; REDUCE


;;;; FILL

Vector and list transforms, and handle these cases:




;;;; REPLACE


;;;; REMOVE, REMOVE-IF, REMOVE-IF-NOT


;;;; DELETE, DELETE-IF, DELETE-IF-NOT


;;;; REMOVE-DUPLICATES, DELETE-DUPLICATES


;;;; SUBSTITUTE, SUBSTITUTE-IF, SUBSTITUTE-IF-NOT


;;;; NSUBSTITUTE, NSUBSTITUTE-IF, NSUBSTITUTE-IF-NOT


;;;; FIND, FIND-IF, FIND-IF-NOT


;;;; POSITION, POSITION-IF, POSITION-IF-NOT


;;;; COUNT, COUNT-IF, COUNT-IF-NOT


;;;; MISMATCH


;;;; SEARCH