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: prep-car-compare @ car rot @ car 2swap ;

: cell- 1 cells - ;
: str<=  compare dup 0= swap 0< or ; 
: str> compare 0> ;

: partition ( left right -- L1 R1 L2 R2 )
    2dup 2>r				\ retain L1 R2
    dup >r cell-
    begin 2dup < while
	    swap ( right left )
	    begin dup r@ prep-car-compare str<= while  cell+ repeat
	    swap
	    begin dup r@ prep-car-compare str> while cell- repeat
	    2dup < if 2dup exchange then
    repeat
    r> drop
    ( L2 R1 )
    r> swap r> swap 2swap
    ( L1 R1 L2 R2 )
    \ pivot is at R2
    cell- ;