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1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 | ;;;;;; SRFI 43: Vector library -*- Scheme -*-
;;; Taylor Campbell wrote this code; he places it in the public domain.
;; ChangeLog
;;
;; 2007-08-28 yamaken - Imported from
;; http://srfi.schemers.org/srfi-43/vector-lib.scm
;; and adapted to SigScheme
;; 2007-09-08 yamaken - Fix an incorrect error message in check-indices
;;; --------------------
;;; Exported procedure index
;;;
;;; * Constructors
;;; make-vector vector
;;; vector-unfold vector-unfold-right
;;; vector-copy vector-reverse-copy
;;; vector-append vector-concatenate
;;;
;;; * Predicates
;;; vector?
;;; vector-empty?
;;; vector=
;;;
;;; * Selectors
;;; vector-ref
;;; vector-length
;;;
;;; * Iteration
;;; vector-fold vector-fold-right
;;; vector-map vector-map!
;;; vector-for-each
;;; vector-count
;;;
;;; * Searching
;;; vector-index vector-skip
;;; vector-index-right vector-skip-right
;;; vector-binary-search
;;; vector-any vector-every
;;;
;;; * Mutators
;;; vector-set!
;;; vector-swap!
;;; vector-fill!
;;; vector-reverse!
;;; vector-copy! vector-reverse-copy!
;;; vector-reverse!
;;;
;;; * Conversion
;;; vector->list reverse-vector->list
;;; list->vector reverse-list->vector
;;; --------------------
;;; Commentary on efficiency of the code
;;; This code is somewhat tuned for efficiency. There are several
;;; internal routines that can be optimized greatly to greatly improve
;;; the performance of much of the library. These internal procedures
;;; are already carefully tuned for performance, and lambda-lifted by
;;; hand. Some other routines are lambda-lifted by hand, but only the
;;; loops are lambda-lifted, and only if some routine has two possible
;;; loops -- a fast path and an n-ary case --, whereas _all_ of the
;;; internal routines' loops are lambda-lifted so as to never cons a
;;; closure in their body (VECTOR-PARSE-START+END doesn't have a loop),
;;; even in Scheme systems that perform no loop optimization (which is
;;; most of them, unfortunately).
;;;
;;; Fast paths are provided for common cases in most of the loops in
;;; this library.
;;;
;;; All calls to primitive vector operations are protected by a prior
;;; type check; they can be safely converted to use unsafe equivalents
;;; of the operations, if available. Ideally, the compiler should be
;;; able to determine this, but the state of Scheme compilers today is
;;; not a happy one.
;;;
;;; Efficiency of the actual algorithms is a rather mundane point to
;;; mention; vector operations are rarely beyond being straightforward.
;;; --------------------
;;; Utilities
;;; SigScheme: Use native SRFI-8
;;;;; SRFI 8, too trivial to put in the dependencies list.
;;(define-syntax receive
;; (syntax-rules ()
;; ((receive ?formals ?producer ?body1 ?body2 ...)
;; (call-with-values (lambda () ?producer)
;; (lambda ?formals ?body1 ?body2 ...)))))
;;; SigScheme: Define let*-optionals as an alias to let-optionals*
;;;;; Not the best LET*-OPTIONALS, but not the worst, either. Use Olin's
;;;;; if it's available to you.
;;(define-syntax let*-optionals
;; (syntax-rules ()
;; ((let*-optionals (?x ...) ((?var ?default) ...) ?body1 ?body2 ...)
;; (let ((args (?x ...)))
;; (let*-optionals args ((?var ?default) ...) ?body1 ?body2 ...)))
;; ((let*-optionals ?args ((?var ?default) ...) ?body1 ?body2 ...)
;; (let*-optionals:aux ?args ?args ((?var ?default) ...)
;; ?body1 ?body2 ...))))
;;
;;(define-syntax let*-optionals:aux
;; (syntax-rules ()
;; ((aux ?orig-args-var ?args-var () ?body1 ?body2 ...)
;; (if (null? ?args-var)
;; (let () ?body1 ?body2 ...)
;; (error "too many arguments" (length ?orig-args-var)
;; ?orig-args-var)))
;; ((aux ?orig-args-var ?args-var
;; ((?var ?default) ?more ...)
;; ?body1 ?body2 ...)
;; (if (null? ?args-var)
;; (let* ((?var ?default) ?more ...) ?body1 ?body2 ...)
;; (let ((?var (car ?args-var))
;; (new-args (cdr ?args-var)))
;; (let*-optionals:aux ?orig-args-var new-args
;; (?more ...)
;; ?body1 ?body2 ...))))))
(define (nonneg-int? x)
(and (integer? x)
(not (negative? x))))
(define (between? x y z)
(and (< x y)
(<= y z)))
(define (unspecified-value) (if #f #f))
;++ This should be implemented more efficiently. It shouldn't cons a
;++ closure, and the cons cells used in the loops when using this could
;++ be reused.
(define (vectors-ref vectors i)
(map (lambda (v) (vector-ref v i)) vectors))
;;; --------------------
;;; Error checking
;;; Error signalling (not checking) is done in a way that tries to be
;;; as helpful to the person who gets the debugging prompt as possible.
;;; That said, error _checking_ tries to be as unredundant as possible.
;;; I don't use any sort of general condition mechanism; I use simply
;;; SRFI 23's ERROR, even in cases where it might be better to use such
;;; a general condition mechanism. Fix that when porting this to a
;;; Scheme implementation that has its own condition system.
;;; In argument checks, upon receiving an invalid argument, the checker
;;; procedure recursively calls itself, but in one of the arguments to
;;; itself is a call to ERROR; this mechanism is used in the hopes that
;;; the user may be thrown into a debugger prompt, proceed with another
;;; value, and let it be checked again.
;;; Type checking is pretty basic, but easily factored out and replaced
;;; with whatever your implementation's preferred type checking method
;;; is. I doubt there will be many other methods of index checking,
;;; though the index checkers might be better implemented natively.
;;; (CHECK-TYPE <type-predicate?> <value> <callee>) -> value
;;; Ensure that VALUE satisfies TYPE-PREDICATE?; if not, signal an
;;; error stating that VALUE did not satisfy TYPE-PREDICATE?, showing
;;; that this happened while calling CALLEE. Return VALUE if no
;;; error was signalled.
(define (check-type pred? value callee)
(if (pred? value)
value
;; Recur: when (or if) the user gets a debugger prompt, he can
;; proceed where the call to ERROR was with the correct value.
(check-type pred?
(error "erroneous value"
(list pred? value)
`(while calling ,callee))
callee)))
;;; (CHECK-INDEX <vector> <index> <callee>) -> index
;;; Ensure that INDEX is a valid index into VECTOR; if not, signal an
;;; error stating that it is not and that this happened in a call to
;;; CALLEE. Return INDEX when it is valid. (Note that this does NOT
;;; check that VECTOR is indeed a vector.)
(define (check-index vec index callee)
(let ((index (check-type integer? index callee)))
(cond ((< index 0)
(check-index vec
(error "vector index too low"
index
`(into vector ,vec)
`(while calling ,callee))
callee))
((>= index (vector-length vec))
(check-index vec
(error "vector index too high"
index
`(into vector ,vec)
`(while calling ,callee))
callee))
(else index))))
;;; (CHECK-INDICES <vector>
;;; <start> <start-name>
;;; <end> <end-name>
;;; <caller>) -> [start end]
;;; Ensure that START and END are valid bounds of a range within
;;; VECTOR; if not, signal an error stating that they are not, with
;;; the message being informative about what the argument names were
;;; called -- by using START-NAME & END-NAME --, and that it occurred
;;; while calling CALLEE. Also ensure that VEC is in fact a vector.
;;; Returns no useful value.
(define (check-indices vec start start-name end end-name callee)
(let ((lose (lambda things
(apply error "vector range out of bounds"
(append things
`(vector was ,vec)
`(,start-name was ,start)
`(,end-name was ,end)
`(while calling ,callee)))))
(start (check-type integer? start callee))
(end (check-type integer? end callee)))
(cond ((> start end)
;; I'm not sure how well this will work. The intent is that
;; the programmer tells the debugger to proceed with both a
;; new START & a new END by returning multiple values
;; somewhere.
(receive (new-start new-end)
(lose `(,end-name < ,start-name))
(check-indices vec
new-start start-name
new-end end-name
callee)))
((< start 0)
(check-indices vec
(lose `(,start-name < 0))
start-name
end end-name
callee))
((>= start (vector-length vec))
(check-indices vec
(lose `(,start-name >= len)
`(len was ,(vector-length vec)))
start-name
end end-name
callee))
((> end (vector-length vec))
(check-indices vec
start start-name
(lose `(,end-name > len)
`(len was ,(vector-length vec)))
end-name
callee))
(else
(values start end)))))
;;; --------------------
;;; Internal routines
;;; These should all be integrated, native, or otherwise optimized --
;;; they're used a _lot_ --. All of the loops and LETs inside loops
;;; are lambda-lifted by hand, just so as not to cons closures in the
;;; loops. (If your compiler can do better than that if they're not
;;; lambda-lifted, then lambda-drop (?) them.)
;;; (VECTOR-PARSE-START+END <vector> <arguments>
;;; <start-name> <end-name>
;;; <callee>)
;;; -> [start end]
;;; Return two values, composing a valid range within VECTOR, as
;;; extracted from ARGUMENTS or defaulted from VECTOR -- 0 for START
;;; and the length of VECTOR for END --; START-NAME and END-NAME are
;;; purely for error checking.
(define (vector-parse-start+end vec args start-name end-name callee)
(let ((len (vector-length vec)))
(cond ((null? args)
(values 0 len))
((null? (cdr args))
(check-indices vec
(car args) start-name
len end-name
callee))
((null? (cddr args))
(check-indices vec
(car args) start-name
(cadr args) end-name
callee))
(else
(error "too many arguments"
`(extra args were ,(cddr args))
`(while calling ,callee))))))
;;; SigScheme: Defined in module-srfi43.c
;;(define-syntax let-vector-start+end
;; (syntax-rules ()
;; ((let-vector-start+end ?callee ?vec ?args (?start ?end)
;; ?body1 ?body2 ...)
;; (let ((?vec (check-type vector? ?vec ?callee)))
;; (receive (?start ?end)
;; (vector-parse-start+end ?vec ?args '?start '?end
;; ?callee)
;; ?body1 ?body2 ...)))))
;;; (%SMALLEST-LENGTH <vector-list> <default-length> <callee>)
;;; -> exact, nonnegative integer
;;; Compute the smallest length of VECTOR-LIST. DEFAULT-LENGTH is
;;; the length that is returned if VECTOR-LIST is empty. Common use
;;; of this is in n-ary vector routines:
;;; (define (f vec . vectors)
;;; (let ((vec (check-type vector? vec f)))
;;; ...(%smallest-length vectors (vector-length vec) f)...))
;;; %SMALLEST-LENGTH takes care of the type checking -- which is what
;;; the CALLEE argument is for --; thus, the design is tuned for
;;; avoiding redundant type checks.
(define %smallest-length
(letrec ((loop (lambda (vector-list length callee)
(if (null? vector-list)
length
(loop (cdr vector-list)
(min (vector-length
(check-type vector?
(car vector-list)
callee))
length)
callee)))))
loop))
;;; (%VECTOR-COPY! <target> <tstart> <source> <sstart> <send>)
;;; Copy elements at locations SSTART to SEND from SOURCE to TARGET,
;;; starting at TSTART in TARGET.
;;;
;;; Optimize this! Probably with some combination of:
;;; - Force it to be integrated.
;;; - Let it use unsafe vector element dereferencing routines: bounds
;;; checking already happens outside of it. (Or use a compiler
;;; that figures this out, but Olin Shivers' PhD thesis seems to
;;; have been largely ignored in actual implementations...)
;;; - Implement it natively as a VM primitive: the VM can undoubtedly
;;; perform much faster than it can make Scheme perform, even with
;;; bounds checking.
;;; - Implement it in assembly: you _want_ the fine control that
;;; assembly can give you for this.
;;; I already lambda-lift it by hand, but you should be able to make it
;;; even better than that.
(define %vector-copy!
(letrec ((loop/l->r (lambda (target source send i j)
(cond ((< i send)
(vector-set! target j
(vector-ref source i))
(loop/l->r target source send
(+ i 1) (+ j 1))))))
(loop/r->l (lambda (target source sstart i j)
(cond ((>= i sstart)
(vector-set! target j
(vector-ref source i))
(loop/r->l target source sstart
(- i 1) (- j 1)))))))
(lambda (target tstart source sstart send)
(if (> sstart tstart) ; Make sure we don't copy over
; ourselves.
(loop/l->r target source send sstart tstart)
(loop/r->l target source sstart (- send 1)
(+ -1 tstart send (- sstart)))))))
;;; (%VECTOR-REVERSE-COPY! <target> <tstart> <source> <sstart> <send>)
;;; Copy elements from SSTART to SEND from SOURCE to TARGET, in the
;;; reverse order.
(define %vector-reverse-copy!
(letrec ((loop (lambda (target source sstart i j)
(cond ((>= i sstart)
(vector-set! target j (vector-ref source i))
(loop target source sstart
(- i 1)
(+ j 1)))))))
(lambda (target tstart source sstart send)
(loop target source sstart
(- send 1)
tstart))))
;;; (%VECTOR-REVERSE! <vector>)
(define %vector-reverse!
(letrec ((loop (lambda (vec i j)
(cond ((<= i j)
(let ((v (vector-ref vec i)))
(vector-set! vec i (vector-ref vec j))
(vector-set! vec j v)
(loop vec (+ i 1) (- j 1))))))))
(lambda (vec start end)
(loop vec start (- end 1)))))
;;; (%VECTOR-FOLD1 <kons> <knil> <vector>) -> knil'
;;; (KONS <index> <knil> <elt>) -> knil'
(define %vector-fold1
(letrec ((loop (lambda (kons knil len vec i)
(if (= i len)
knil
(loop kons
(kons i knil (vector-ref vec i))
len vec (+ i 1))))))
(lambda (kons knil len vec)
(loop kons knil len vec 0))))
;;; (%VECTOR-FOLD2+ <kons> <knil> <vector> ...) -> knil'
;;; (KONS <index> <knil> <elt> ...) -> knil'
(define %vector-fold2+
(letrec ((loop (lambda (kons knil len vectors i)
(if (= i len)
knil
(loop kons
(apply kons i knil
(vectors-ref vectors i))
len vectors (+ i 1))))))
(lambda (kons knil len vectors)
(loop kons knil len vectors 0))))
;;; (%VECTOR-MAP! <f> <target> <length> <vector>) -> target
;;; (F <index> <elt>) -> elt'
(define %vector-map1!
(letrec ((loop (lambda (f target vec i)
(if (zero? i)
target
(let ((j (- i 1)))
(vector-set! target j
(f j (vector-ref vec j)))
(loop f target vec j))))))
(lambda (f target vec len)
(loop f target vec len))))
;;; (%VECTOR-MAP2+! <f> <target> <vectors> <len>) -> target
;;; (F <index> <elt> ...) -> elt'
(define %vector-map2+!
(letrec ((loop (lambda (f target vectors i)
(if (zero? i)
target
(let ((j (- i 1)))
(vector-set! target j
(apply f j (vectors-ref vectors j)))
(loop f target vectors j))))))
(lambda (f target vectors len)
(loop f target vectors len))))
;;;;;;;;;;;;;;;;;;;;;;;; ***** vector-lib ***** ;;;;;;;;;;;;;;;;;;;;;;;
;;; --------------------
;;; Constructors
;;; (MAKE-VECTOR <size> [<fill>]) -> vector
;;; [R5RS] Create a vector of length LENGTH. If FILL is present,
;;; initialize each slot in the vector with it; if not, the vector's
;;; initial contents are unspecified.
(define make-vector make-vector)
;;; (VECTOR <elt> ...) -> vector
;;; [R5RS] Create a vector containing ELEMENT ..., in order.
(define vector vector)
;;; This ought to be able to be implemented much more efficiently -- if
;;; we have the number of arguments available to us, we can create the
;;; vector without using LENGTH to determine the number of elements it
;;; should have.
;(define (vector . elements) (list->vector elements))
;;; (VECTOR-UNFOLD <f> <length> <initial-seed> ...) -> vector
;;; (F <index> <seed> ...) -> [elt seed' ...]
;;; The fundamental vector constructor. Creates a vector whose
;;; length is LENGTH and iterates across each index K between 0 and
;;; LENGTH, applying F at each iteration to the current index and the
;;; current seeds to receive N+1 values: first, the element to put in
;;; the Kth slot and then N new seeds for the next iteration.
(define vector-unfold
(letrec ((tabulate! ; Special zero-seed case.
(lambda (f vec i len)
(cond ((< i len)
(vector-set! vec i (f i))
(tabulate! f vec (+ i 1) len)))))
(unfold1! ; Fast path for one seed.
(lambda (f vec i len seed)
(if (< i len)
(receive (elt new-seed)
(f i seed)
(vector-set! vec i elt)
(unfold1! f vec (+ i 1) len new-seed)))))
(unfold2+! ; Slower variant for N seeds.
(lambda (f vec i len seeds)
(if (< i len)
(receive (elt . new-seeds)
(apply f i seeds)
(vector-set! vec i elt)
(unfold2+! f vec (+ i 1) len new-seeds))))))
(lambda (f len . initial-seeds)
(let ((f (check-type procedure? f vector-unfold))
(len (check-type nonneg-int? len vector-unfold)))
(let ((vec (make-vector len)))
(cond ((null? initial-seeds)
(tabulate! f vec 0 len))
((null? (cdr initial-seeds))
(unfold1! f vec 0 len (car initial-seeds)))
(else
(unfold2+! f vec 0 len initial-seeds)))
vec)))))
;;; (VECTOR-UNFOLD-RIGHT <f> <length> <initial-seed> ...) -> vector
;;; (F <seed> ...) -> [seed' ...]
;;; Like VECTOR-UNFOLD, but it generates elements from LENGTH to 0
;;; (still exclusive with LENGTH and inclusive with 0), not 0 to
;;; LENGTH as with VECTOR-UNFOLD.
(define vector-unfold-right
(letrec ((tabulate!
(lambda (f vec i)
(cond ((>= i 0)
(vector-set! vec i (f i))
(tabulate! f vec (- i 1))))))
(unfold1!
(lambda (f vec i seed)
(if (>= i 0)
(receive (elt new-seed)
(f i seed)
(vector-set! vec i elt)
(unfold1! f vec (- i 1) new-seed)))))
(unfold2+!
(lambda (f vec i seeds)
(if (>= i 0)
(receive (elt . new-seeds)
(apply f i seeds)
(vector-set! vec i elt)
(unfold2+! f vec (- i 1) new-seeds))))))
(lambda (f len . initial-seeds)
(let ((f (check-type procedure? f vector-unfold-right))
(len (check-type nonneg-int? len vector-unfold-right)))
(let ((vec (make-vector len))
(i (- len 1)))
(cond ((null? initial-seeds)
(tabulate! f vec i))
((null? (cdr initial-seeds))
(unfold1! f vec i (car initial-seeds)))
(else
(unfold2+! f vec i initial-seeds)))
vec)))))
;;; (VECTOR-COPY <vector> [<start> <end> <fill>]) -> vector
;;; Create a newly allocated vector containing the elements from the
;;; range [START,END) in VECTOR. START defaults to 0; END defaults
;;; to the length of VECTOR. END may be greater than the length of
;;; VECTOR, in which case the vector is enlarged; if FILL is passed,
;;; the new locations from which there is no respective element in
;;; VECTOR are filled with FILL.
(define (vector-copy vec . args)
(let ((vec (check-type vector? vec vector-copy)))
;; We can't use LET-VECTOR-START+END, because we have one more
;; argument, and we want finer control, too.
;;
;; Olin's implementation of LET*-OPTIONALS would prove useful here:
;; the built-in argument-checks-as-you-go-along produces almost
;; _exactly_ the same code as VECTOR-COPY:PARSE-ARGS.
(receive (start end fill)
(vector-copy:parse-args vec args)
(let ((new-vector (make-vector (- end start) fill)))
(%vector-copy! new-vector 0
vec start
(if (> end (vector-length vec))
(vector-length vec)
end))
new-vector))))
;;; Auxiliary for VECTOR-COPY.
(define (vector-copy:parse-args vec args)
(if (null? args)
(values 0 (vector-length vec) (unspecified-value))
(let ((start (check-index vec (car args) vector-copy)))
(if (null? (cdr args))
(values start (vector-length vec) (unspecified-value))
(let ((end (check-type nonneg-int? (cadr args)
vector-copy)))
(cond ((>= start (vector-length vec))
(error "start bound out of bounds"
`(start was ,start)
`(end was ,end)
`(vector was ,vec)
`(while calling ,vector-copy)))
((> start end)
(error "can't invert a vector copy!"
`(start was ,start)
`(end was ,end)
`(vector was ,vec)
`(while calling ,vector-copy)))
((null? (cddr args))
(values start end (unspecified-value)))
(else
(let ((fill (caddr args)))
(if (null? (cdddr args))
(values start end fill)
(error "too many arguments"
vector-copy
(cdddr args)))))))))))
;;; (VECTOR-REVERSE-COPY <vector> [<start> <end>]) -> vector
;;; Create a newly allocated vector whose elements are the reversed
;;; sequence of elements between START and END in VECTOR. START's
;;; default is 0; END's default is the length of VECTOR.
(define (vector-reverse-copy vec . maybe-start+end)
(let-vector-start+end vector-reverse-copy vec maybe-start+end
(start end)
(let ((new (make-vector (- end start))))
(%vector-reverse-copy! new 0 vec start end)
new)))
;;; (VECTOR-APPEND <vector> ...) -> vector
;;; Append VECTOR ... into a newly allocated vector and return that
;;; new vector.
(define (vector-append . vectors)
(vector-concatenate:aux vectors vector-append))
;;; (VECTOR-CONCATENATE <vector-list>) -> vector
;;; Concatenate the vectors in VECTOR-LIST. This is equivalent to
;;; (apply vector-append VECTOR-LIST)
;;; but VECTOR-APPEND tends to be implemented in terms of
;;; VECTOR-CONCATENATE, and some Schemes bork when the list to apply
;;; a function to is too long.
;;;
;;; Actually, they're both implemented in terms of an internal routine.
(define (vector-concatenate vector-list)
(vector-concatenate:aux vector-list vector-concatenate))
;;; Auxiliary for VECTOR-APPEND and VECTOR-CONCATENATE
(define vector-concatenate:aux
(letrec ((compute-length
(lambda (vectors len callee)
(if (null? vectors)
len
(let ((vec (check-type vector? (car vectors)
callee)))
(compute-length (cdr vectors)
(+ (vector-length vec) len)
callee)))))
(concatenate!
(lambda (vectors target to)
(if (null? vectors)
target
(let* ((vec1 (car vectors))
(len (vector-length vec1)))
(%vector-copy! target to vec1 0 len)
(concatenate! (cdr vectors) target
(+ to len)))))))
(lambda (vectors callee)
(cond ((null? vectors) ;+++
(make-vector 0))
((null? (cdr vectors)) ;+++
;; Blech, we still have to allocate a new one.
(let* ((vec (check-type vector? (car vectors) callee))
(len (vector-length vec))
(new (make-vector len)))
(%vector-copy! new 0 vec 0 len)
new))
(else
(let ((new-vector
(make-vector (compute-length vectors 0 callee))))
(concatenate! vectors new-vector 0)
new-vector))))))
;;; --------------------
;;; Predicates
;;; (VECTOR? <value>) -> boolean
;;; [R5RS] Return #T if VALUE is a vector and #F if not.
(define vector? vector?)
;;; (VECTOR-EMPTY? <vector>) -> boolean
;;; Return #T if VECTOR has zero elements in it, i.e. VECTOR's length
;;; is 0, and #F if not.
(define (vector-empty? vec)
(let ((vec (check-type vector? vec vector-empty?)))
(zero? (vector-length vec))))
;;; (VECTOR= <elt=?> <vector> ...) -> boolean
;;; (ELT=? <value> <value>) -> boolean
;;; Determine vector equality generalized across element comparators.
;;; Vectors A and B are equal iff their lengths are the same and for
;;; each respective elements E_a and E_b (element=? E_a E_b) returns
;;; a true value. ELT=? is always applied to two arguments. Element
;;; comparison must be consistent wtih EQ?; that is, if (eq? E_a E_b)
;;; results in a true value, then (ELEMENT=? E_a E_b) must result in a
;;; true value. This may be exploited to avoid multiple unnecessary
;;; element comparisons. (This implementation does, but does not deal
;;; with the situation that ELEMENT=? is EQ? to avoid more unnecessary
;;; comparisons, but I believe this optimization is probably fairly
;;; insignificant.)
;;;
;;; If the number of vector arguments is zero or one, then #T is
;;; automatically returned. If there are N vector arguments,
;;; VECTOR_1 VECTOR_2 ... VECTOR_N, then VECTOR_1 & VECTOR_2 are
;;; compared; if they are equal, the vectors VECTOR_2 ... VECTOR_N
;;; are compared. The precise order in which ELT=? is applied is not
;;; specified.
(define (vector= elt=? . vectors)
(let ((elt=? (check-type procedure? elt=? vector=)))
(cond ((null? vectors)
#t)
((null? (cdr vectors))
(check-type vector? (car vectors) vector=)
#t)
(else
(let loop ((vecs vectors))
(let ((vec1 (check-type vector? (car vecs) vector=))
(vec2+ (cdr vecs)))
(or (null? vec2+)
(and (binary-vector= elt=? vec1 (car vec2+))
(loop vec2+)))))))))
(define (binary-vector= elt=? vector-a vector-b)
(or (eq? vector-a vector-b) ;+++
(let ((length-a (vector-length vector-a))
(length-b (vector-length vector-b)))
(letrec ((loop (lambda (i)
(or (= i length-a)
(and (< i length-b)
(test (vector-ref vector-a i)
(vector-ref vector-b i)
i)))))
(test (lambda (elt-a elt-b i)
(and (or (eq? elt-a elt-b) ;+++
(elt=? elt-a elt-b))
(loop (+ i 1))))))
(and (= length-a length-b)
(loop 0))))))
;;; --------------------
;;; Selectors
;;; (VECTOR-REF <vector> <index>) -> value
;;; [R5RS] Return the value that the location in VECTOR at INDEX is
;;; mapped to in the store.
(define vector-ref vector-ref)
;;; (VECTOR-LENGTH <vector>) -> exact, nonnegative integer
;;; [R5RS] Return the length of VECTOR.
(define vector-length vector-length)
;;; --------------------
;;; Iteration
;;; (VECTOR-FOLD <kons> <initial-knil> <vector> ...) -> knil
;;; (KONS <knil> <elt> ...) -> knil' ; N vectors -> N+1 args
;;; The fundamental vector iterator. KONS is iterated over each
;;; index in all of the vectors in parallel, stopping at the end of
;;; the shortest; KONS is applied to an argument list of (list I
;;; STATE (vector-ref VEC I) ...), where STATE is the current state
;;; value -- the state value begins with KNIL and becomes whatever
;;; KONS returned at the respective iteration --, and I is the
;;; current index in the iteration. The iteration is strictly left-
;;; to-right.
;;; (vector-fold KONS KNIL (vector E_1 E_2 ... E_N))
;;; <=>
;;; (KONS (... (KONS (KONS KNIL E_1) E_2) ... E_N-1) E_N)
(define (vector-fold kons knil vec . vectors)
(let ((kons (check-type procedure? kons vector-fold))
(vec (check-type vector? vec vector-fold)))
(if (null? vectors)
(%vector-fold1 kons knil (vector-length vec) vec)
(%vector-fold2+ kons knil
(%smallest-length vectors
(vector-length vec)
vector-fold)
(cons vec vectors)))))
;;; (VECTOR-FOLD-RIGHT <kons> <initial-knil> <vector> ...) -> knil
;;; (KONS <knil> <elt> ...) -> knil' ; N vectors => N+1 args
;;; The fundamental vector recursor. Iterates in parallel across
;;; VECTOR ... right to left, applying KONS to the elements and the
;;; current state value; the state value becomes what KONS returns
;;; at each next iteration. KNIL is the initial state value.
;;; (vector-fold-right KONS KNIL (vector E_1 E_2 ... E_N))
;;; <=>
;;; (KONS (... (KONS (KONS KNIL E_N) E_N-1) ... E_2) E_1)
;;;
;;; Not implemented in terms of a more primitive operations that might
;;; called %VECTOR-FOLD-RIGHT due to the fact that it wouldn't be very
;;; useful elsewhere.
(define vector-fold-right
(letrec ((loop1 (lambda (kons knil vec i)
(if (negative? i)
knil
(loop1 kons (kons i knil (vector-ref vec i))
vec
(- i 1)))))
(loop2+ (lambda (kons knil vectors i)
(if (negative? i)
knil
(loop2+ kons
(apply kons i knil
(vectors-ref vectors i))
vectors
(- i 1))))))
(lambda (kons knil vec . vectors)
(let ((kons (check-type procedure? kons vector-fold-right))
(vec (check-type vector? vec vector-fold-right)))
(if (null? vectors)
(loop1 kons knil vec (- (vector-length vec) 1))
(loop2+ kons knil (cons vec vectors)
(- (%smallest-length vectors
(vector-length vec)
vector-fold-right)
1)))))))
;;; (VECTOR-MAP <f> <vector> ...) -> vector
;;; (F <elt> ...) -> value ; N vectors -> N args
;;; Constructs a new vector of the shortest length of the vector
;;; arguments. Each element at index I of the new vector is mapped
;;; from the old vectors by (F I (vector-ref VECTOR I) ...). The
;;; dynamic order of application of F is unspecified.
(define (vector-map f vec . vectors)
(let ((f (check-type procedure? f vector-map))
(vec (check-type vector? vec vector-map)))
(if (null? vectors)
(let ((len (vector-length vec)))
(%vector-map1! f (make-vector len) vec len))
(let ((len (%smallest-length vectors
(vector-length vec)
vector-map)))
(%vector-map2+! f (make-vector len) (cons vec vectors)
len)))))
;;; (VECTOR-MAP! <f> <vector> ...) -> unspecified
;;; (F <elt> ...) -> element' ; N vectors -> N args
;;; Similar to VECTOR-MAP, but rather than mapping the new elements
;;; into a new vector, the new mapped elements are destructively
;;; inserted into the first vector. Again, the dynamic order of
;;; application of F is unspecified, so it is dangerous for F to
;;; manipulate the first VECTOR.
(define (vector-map! f vec . vectors)
(let ((f (check-type procedure? f vector-map!))
(vec (check-type vector? vec vector-map!)))
(if (null? vectors)
(%vector-map1! f vec vec (vector-length vec))
(%vector-map2+! f vec (cons vec vectors)
(%smallest-length vectors
(vector-length vec)
vector-map!)))
(unspecified-value)))
;;; (VECTOR-FOR-EACH <f> <vector> ...) -> unspecified
;;; (F <elt> ...) ; N vectors -> N args
;;; Simple vector iterator: applies F to each index in the range [0,
;;; LENGTH), where LENGTH is the length of the smallest vector
;;; argument passed, and the respective element at that index. In
;;; contrast with VECTOR-MAP, F is reliably applied to each
;;; subsequent elements, starting at index 0 from left to right, in
;;; the vectors.
(define vector-for-each
(letrec ((for-each1
(lambda (f vec i len)
(cond ((< i len)
(f i (vector-ref vec i))
(for-each1 f vec (+ i 1) len)))))
(for-each2+
(lambda (f vecs i len)
(cond ((< i len)
(apply f i (vectors-ref vecs i))
(for-each2+ f vecs (+ i 1) len))))))
(lambda (f vec . vectors)
(let ((f (check-type procedure? f vector-for-each))
(vec (check-type vector? vec vector-for-each)))
(if (null? vectors)
(for-each1 f vec 0 (vector-length vec))
(for-each2+ f (cons vec vectors) 0
(%smallest-length vectors
(vector-length vec)
vector-for-each)))))))
;;; (VECTOR-COUNT <predicate?> <vector> ...)
;;; -> exact, nonnegative integer
;;; (PREDICATE? <index> <value> ...) ; N vectors -> N+1 args
;;; PREDICATE? is applied element-wise to the elements of VECTOR ...,
;;; and a count is tallied of the number of elements for which a
;;; true value is produced by PREDICATE?. This count is returned.
(define (vector-count pred? vec . vectors)
(let ((pred? (check-type procedure? pred? vector-count))
(vec (check-type vector? vec vector-count)))
(if (null? vectors)
(%vector-fold1 (lambda (index count elt)
(if (pred? index elt)
(+ count 1)
count))
0
(vector-length vec)
vec)
(%vector-fold2+ (lambda (index count . elts)
(if (apply pred? index elts)
(+ count 1)
count))
0
(%smallest-length vectors
(vector-length vec)
vector-count)
(cons vec vectors)))))
;;; --------------------
;;; Searching
;;; (VECTOR-INDEX <predicate?> <vector> ...)
;;; -> exact, nonnegative integer or #F
;;; (PREDICATE? <elt> ...) -> boolean ; N vectors -> N args
;;; Search left-to-right across VECTOR ... in parallel, returning the
;;; index of the first set of values VALUE ... such that (PREDICATE?
;;; VALUE ...) returns a true value; if no such set of elements is
;;; reached, return #F.
(define (vector-index pred? vec . vectors)
(vector-index/skip pred? vec vectors vector-index))
;;; (VECTOR-SKIP <predicate?> <vector> ...)
;;; -> exact, nonnegative integer or #F
;;; (PREDICATE? <elt> ...) -> boolean ; N vectors -> N args
;;; (vector-index (lambda elts (not (apply PREDICATE? elts)))
;;; VECTOR ...)
;;; Like VECTOR-INDEX, but find the index of the first set of values
;;; that do _not_ satisfy PREDICATE?.
(define (vector-skip pred? vec . vectors)
(vector-index/skip (lambda elts (not (apply pred? elts)))
vec vectors
vector-skip))
;;; Auxiliary for VECTOR-INDEX & VECTOR-SKIP
(define vector-index/skip
(letrec ((loop1 (lambda (pred? vec len i)
(cond ((= i len) #f)
((pred? (vector-ref vec i)) i)
(else (loop1 pred? vec len (+ i 1))))))
(loop2+ (lambda (pred? vectors len i)
(cond ((= i len) #f)
((apply pred? (vectors-ref vectors i)) i)
(else (loop2+ pred? vectors len
(+ i 1)))))))
(lambda (pred? vec vectors callee)
(let ((pred? (check-type procedure? pred? callee))
(vec (check-type vector? vec callee)))
(if (null? vectors)
(loop1 pred? vec (vector-length vec) 0)
(loop2+ pred? (cons vec vectors)
(%smallest-length vectors
(vector-length vec)
callee)
0))))))
;;; (VECTOR-INDEX-RIGHT <predicate?> <vector> ...)
;;; -> exact, nonnegative integer or #F
;;; (PREDICATE? <elt> ...) -> boolean ; N vectors -> N args
;;; Right-to-left variant of VECTOR-INDEX.
(define (vector-index-right pred? vec . vectors)
(vector-index/skip-right pred? vec vectors vector-index-right))
;;; (VECTOR-SKIP-RIGHT <predicate?> <vector> ...)
;;; -> exact, nonnegative integer or #F
;;; (PREDICATE? <elt> ...) -> boolean ; N vectors -> N args
;;; Right-to-left variant of VECTOR-SKIP.
(define (vector-skip-right pred? vec . vectors)
(vector-index/skip-right (lambda elts (not (apply pred? elts)))
vec vectors
vector-index-right))
(define vector-index/skip-right
(letrec ((loop1 (lambda (pred? vec i)
(cond ((negative? i) #f)
((pred? (vector-ref vec i)) i)
(else (loop1 pred? vec (- i 1))))))
(loop2+ (lambda (pred? vectors i)
(cond ((negative? i) #f)
((apply pred? (vectors-ref vectors i)) i)
(else (loop2+ pred? vectors (- i 1)))))))
(lambda (pred? vec vectors callee)
(let ((pred? (check-type procedure? pred? callee))
(vec (check-type vector? vec callee)))
(if (null? vectors)
(loop1 pred? vec (- (vector-length vec) 1))
(loop2+ pred? (cons vec vectors)
(- (%smallest-length vectors
(vector-length vec)
callee)
1)))))))
;;; (VECTOR-BINARY-SEARCH <vector> <value> <cmp> [<start> <end>])
;;; -> exact, nonnegative integer or #F
;;; (CMP <value1> <value2>) -> integer
;;; positive -> VALUE1 > VALUE2
;;; zero -> VALUE1 = VALUE2
;;; negative -> VALUE1 < VALUE2
;;; Perform a binary search through VECTOR for VALUE, comparing each
;;; element to VALUE with CMP.
(define (vector-binary-search vec value cmp . maybe-start+end)
(let ((cmp (check-type procedure? cmp vector-binary-search)))
(let-vector-start+end vector-binary-search vec maybe-start+end
(start end)
(let loop ((start start) (end end) (j #f))
(let ((i (quotient (+ start end) 2)))
(if (or (= start end) (and j (= i j)))
#f
(let ((comparison
(check-type integer?
(cmp (vector-ref vec i) value)
`(,cmp for ,vector-binary-search))))
(cond ((zero? comparison) i)
((positive? comparison) (loop start i i))
(else (loop i end i))))))))))
;;; (VECTOR-ANY <pred?> <vector> ...) -> value
;;; Apply PRED? to each parallel element in each VECTOR ...; if PRED?
;;; should ever return a true value, immediately stop and return that
;;; value; otherwise, when the shortest vector runs out, return #F.
;;; The iteration and order of application of PRED? across elements
;;; is of the vectors is strictly left-to-right.
(define vector-any
(letrec ((loop1 (lambda (pred? vec i len len-1)
(and (not (= i len))
(if (= i len-1)
(pred? (vector-ref vec i))
(or (pred? (vector-ref vec i))
(loop1 pred? vec (+ i 1)
len len-1))))))
(loop2+ (lambda (pred? vectors i len len-1)
(and (not (= i len))
(if (= i len-1)
(apply pred? (vectors-ref vectors i))
(or (apply pred? (vectors-ref vectors i))
(loop2+ pred? vectors (+ i 1)
len len-1)))))))
(lambda (pred? vec . vectors)
(let ((pred? (check-type procedure? pred? vector-any))
(vec (check-type vector? vec vector-any)))
(if (null? vectors)
(let ((len (vector-length vec)))
(loop1 pred? vec 0 len (- len 1)))
(let ((len (%smallest-length vectors
(vector-length vec)
vector-any)))
(loop2+ pred? (cons vec vectors) 0 len (- len 1))))))))
;;; (VECTOR-EVERY <pred?> <vector> ...) -> value
;;; Apply PRED? to each parallel value in each VECTOR ...; if PRED?
;;; should ever return #F, immediately stop and return #F; otherwise,
;;; if PRED? should return a true value for each element, stopping at
;;; the end of the shortest vector, return the last value that PRED?
;;; returned. In the case that there is an empty vector, return #T.
;;; The iteration and order of application of PRED? across elements
;;; is of the vectors is strictly left-to-right.
(define vector-every
(letrec ((loop1 (lambda (pred? vec i len len-1)
(or (= i len)
(if (= i len-1)
(pred? (vector-ref vec i))
(and (pred? (vector-ref vec i))
(loop1 pred? vec (+ i 1)
len len-1))))))
(loop2+ (lambda (pred? vectors i len len-1)
(or (= i len)
(if (= i len-1)
(apply pred? (vectors-ref vectors i))
(and (apply pred? (vectors-ref vectors i))
(loop2+ pred? vectors (+ i 1)
len len-1)))))))
(lambda (pred? vec . vectors)
(let ((pred? (check-type procedure? pred? vector-every))
(vec (check-type vector? vec vector-every)))
(if (null? vectors)
(let ((len (vector-length vec)))
(loop1 pred? vec 0 len (- len 1)))
(let ((len (%smallest-length vectors
(vector-length vec)
vector-every)))
(loop2+ pred? (cons vec vectors) 0 len (- len 1))))))))
;;; --------------------
;;; Mutators
;;; (VECTOR-SET! <vector> <index> <value>) -> unspecified
;;; [R5RS] Assign the location at INDEX in VECTOR to VALUE.
(define vector-set! vector-set!)
;;; (VECTOR-SWAP! <vector> <index1> <index2>) -> unspecified
;;; Swap the values in the locations at INDEX1 and INDEX2.
(define (vector-swap! vec i j)
(let ((vec (check-type vector? vec vector-swap!)))
(let ((i (check-index vec i vector-swap!))
(j (check-index vec j vector-swap!)))
(let ((x (vector-ref vec i)))
(vector-set! vec i (vector-ref vec j))
(vector-set! vec j x)))))
;;; (VECTOR-FILL! <vector> <value> [<start> <end>]) -> unspecified
;;; [R5RS+] Fill the locations in VECTOR between START, whose default
;;; is 0, and END, whose default is the length of VECTOR, with VALUE.
;;;
;;; This one can probably be made really fast natively.
(define vector-fill!
(let ((%vector-fill! vector-fill!)) ; Take the native one, under
; the assumption that it's
; faster, so we can use it if
; there are no optional
; arguments.
(lambda (vec value . maybe-start+end)
(if (null? maybe-start+end)
(%vector-fill! vec value) ;+++
(let-vector-start+end vector-fill! vec maybe-start+end
(start end)
(do ((i start (+ i 1)))
((= i end))
(vector-set! vec i value)))))))
;;; (VECTOR-COPY! <target> <tstart> <source> [<sstart> <send>])
;;; -> unspecified
;;; Copy the values in the locations in [SSTART,SEND) from SOURCE to
;;; to TARGET, starting at TSTART in TARGET.
(define (vector-copy! target tstart source . maybe-sstart+send)
(let* ((target (check-type vector? target vector-copy!))
(tstart (check-index target tstart vector-copy!)))
(let-vector-start+end vector-copy! source maybe-sstart+send
(sstart send)
(let* ((source-length (vector-length source))
(lose (lambda (argument)
(error "vector range out of bounds"
argument
`(while calling ,vector-copy!)
`(target was ,target)
`(target-length was ,(vector-length target))
`(tstart was ,tstart)
`(source was ,source)
`(source-length was ,source-length)
`(sstart was ,sstart)
`(send was ,send)))))
(cond ((< sstart 0)
(lose '(sstart < 0)))
((< send 0)
(lose '(send < 0)))
((> sstart send)
(lose '(sstart > send)))
((>= sstart source-length)
(lose '(sstart >= source-length)))
((> send source-length)
(lose '(send > source-length)))
(else
(%vector-copy! target tstart
source sstart send)))))))
;;; (VECTOR-REVERSE-COPY! <target> <tstart> <source> [<sstart> <send>])
(define (vector-reverse-copy! target tstart source . maybe-sstart+send)
(let* ((target (check-type vector? target vector-reverse-copy!))
(tstart (check-index target tstart vector-reverse-copy!)))
(let-vector-start+end vector-reverse-copy source maybe-sstart+send
(sstart send)
(let* ((source-length (vector-length source))
(lose (lambda (argument)
(error "vector range out of bounds"
argument
`(while calling ,vector-reverse-copy!)
`(target was ,target)
`(target-length was ,(vector-length target))
`(tstart was ,tstart)
`(source was ,source)
`(source-length was ,source-length)
`(sstart was ,sstart)
`(send was ,send)))))
(cond ((< sstart 0)
(lose '(sstart < 0)))
((< send 0)
(lose '(send < 0)))
((> sstart send)
(lose '(sstart > send)))
((>= sstart source-length)
(lose '(sstart >= source-length)))
((> send source-length)
(lose '(send > source-length)))
((and (eq? target source)
(= sstart tstart))
(%vector-reverse! target tstart send))
((and (eq? target source)
(or (between? sstart tstart send)
(between? tstart sstart
(+ tstart (- send sstart)))))
(error "vector range for self-copying overlaps"
vector-reverse-copy!
`(vector was ,target)
`(tstart was ,tstart)
`(sstart was ,sstart)
`(send was ,send)))
(else
(%vector-reverse-copy! target tstart
source sstart send)))))))
;;; (VECTOR-REVERSE! <vector> [<start> <end>]) -> unspecified
;;; Destructively reverse the contents of the sequence of locations
;;; in VECTOR between START, whose default is 0, and END, whose
;;; default is the length of VECTOR.
(define (vector-reverse! vec . start+end)
(let-vector-start+end vector-reverse! vec start+end
(start end)
(%vector-reverse! vec start end)))
;;; --------------------
;;; Conversion
;;; (VECTOR->LIST <vector> [<start> <end>]) -> list
;;; [R5RS+] Produce a list containing the elements in the locations
;;; between START, whose default is 0, and END, whose default is the
;;; length of VECTOR, from VECTOR.
(define vector->list
(let ((%vector->list vector->list))
(lambda (vec . maybe-start+end)
(if (null? maybe-start+end) ; Oughta use CASE-LAMBDA.
(%vector->list vec) ;+++
(let-vector-start+end vector->list vec maybe-start+end
(start end)
;(unfold (lambda (i) ; No SRFI 1.
; (< i start))
; (lambda (i) (vector-ref vec i))
; (lambda (i) (- i 1))
; (- end 1))
(do ((i (- end 1) (- i 1))
(result '() (cons (vector-ref vec i) result)))
((< i start) result)))))))
;;; (REVERSE-VECTOR->LIST <vector> [<start> <end>]) -> list
;;; Produce a list containing the elements in the locations between
;;; START, whose default is 0, and END, whose default is the length
;;; of VECTOR, from VECTOR, in reverse order.
(define (reverse-vector->list vec . maybe-start+end)
(let-vector-start+end reverse-vector->list vec maybe-start+end
(start end)
;(unfold (lambda (i) (= i end)) ; No SRFI 1.
; (lambda (i) (vector-ref vec i))
; (lambda (i) (+ i 1))
; start)
(do ((i start (+ i 1))
(result '() (cons (vector-ref vec i) result)))
((= i end) result))))
;;; (LIST->VECTOR <list> [<start> <end>]) -> vector
;;; [R5RS+] Produce a vector containing the elements in LIST, which
;;; must be a proper list, between START, whose default is 0, & END,
;;; whose default is the length of LIST. It is suggested that if the
;;; length of LIST is known in advance, the START and END arguments
;;; be passed, so that LIST->VECTOR need not call LENGTH to determine
;;; the the length.
;;;
;;; This implementation diverges on circular lists, unless LENGTH fails
;;; and causes - to fail as well. Given a LENGTH* that computes the
;;; length of a list's cycle, this wouldn't diverge, and would work
;;; great for circular lists.
(define list->vector
(let ((%list->vector list->vector))
(lambda (lst . maybe-start+end)
;; Checking the type of a proper list is expensive, so we do it
;; amortizedly, or let %LIST->VECTOR or LIST-TAIL do it.
(if (null? maybe-start+end) ; Oughta use CASE-LAMBDA.
(%list->vector lst) ;+++
;; We can't use LET-VECTOR-START+END, because we're using the
;; bounds of a _list_, not a vector.
(let*-optionals maybe-start+end
((start 0)
(end (length lst))) ; Ugh -- LENGTH
(let ((start (check-type nonneg-int? start list->vector))
(end (check-type nonneg-int? end list->vector)))
((lambda (f)
(vector-unfold f (- end start) (list-tail lst start)))
(lambda (index l)
(cond ((null? l)
(error "list was too short"
`(list was ,lst)
`(attempted end was ,end)
`(while calling ,list->vector)))
((pair? l)
(values (car l) (cdr l)))
(else
;; Make this look as much like what CHECK-TYPE
;; would report as possible.
(error "erroneous value"
;; We want SRFI 1's PROPER-LIST?, but it
;; would be a waste to link all of SRFI
;; 1 to this module for only the single
;; function PROPER-LIST?.
(list list? lst)
`(while calling
,list->vector))))))))))))
;;; (REVERSE-LIST->VECTOR <list> [<start> <end>]) -> vector
;;; Produce a vector containing the elements in LIST, which must be a
;;; proper list, between START, whose default is 0, and END, whose
;;; default is the length of LIST, in reverse order. It is suggested
;;; that if the length of LIST is known in advance, the START and END
;;; arguments be passed, so that REVERSE-LIST->VECTOR need not call
;;; LENGTH to determine the the length.
;;;
;;; This also diverges on circular lists unless, again, LENGTH returns
;;; something that makes - bork.
(define (reverse-list->vector lst . maybe-start+end)
(let*-optionals maybe-start+end
((start 0)
(end (length lst))) ; Ugh -- LENGTH
(let ((start (check-type nonneg-int? start reverse-list->vector))
(end (check-type nonneg-int? end reverse-list->vector)))
((lambda (f)
(vector-unfold-right f (- end start) (list-tail lst start)))
(lambda (index l)
(cond ((null? l)
(error "list too short"
`(list was ,lst)
`(attempted end was ,end)
`(while calling ,reverse-list->vector)))
((pair? l)
(values (car l) (cdr l)))
(else
(error "erroneous value"
(list list? lst)
`(while calling ,reverse-list->vector)))))))))
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