replace

(replace sequence-1 sequence-2 &key start1 end1 start2 end2)

Copies the elements of sequence-2 (bounded by :start2/:end2) into sequence-1 (bounded by :start1/:end1) and returns the result. The number of elements copied is the smaller of the two bounded lengths. A nil :end1/:end2 means the length; a bound outside its sequence -- negative, not an integer, past its length, or a start past its end -- signals a type-error before anything is copied. A vector sequence-1 -- including a string allocated by make-string or make-array :element-type 'character -- is mutated in place and returned, as in CL, so the "allocate a buffer, write into it, return it" idiom works on every backend. A list sequence-1 is likewise rewritten in place, through its cons cells. A string LITERAL is supported as sequence-1 too (the case cl-who needs), but a literal denotes a source constant that is never written on any backend: the copy lands on a fresh string, which comes back as the return value, and sequence-1 itself is left holding the original. When sequence-1 and sequence-2 are the same object and the regions overlap, the result is as if the source region were copied to a temporary first. Available on all backends except --no-gc.