how to remove all elements from an array
in [Lisp]
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From: Joshua Taylor on 6 Mar 2010 13:26 Slobodan Blazeski wrote: > On Mar 6, 7:14 pm, Slobodan Blazeski <slobodan.blaze...(a)gmail.com> > wrote: >> On Mar 6, 7:09 pm, Ron Garret <rNOSPA...(a)flownet.com> wrote: >> >> >> >>> In article >>> <7d69ae1c-2467-4298-974e-6fc98e646...(a)t23g2000yqt.googlegroups.com>, >>> Slobodan Blazeski <slobodan.blaze...(a)gmail.com> wrote: >>>> I have an array defined as: >>>> (make-array 0 :element-type 'string :fill-pointer 0 >>>> :adjustable t) >>>> After adding some elements I want to know how to clear it , i.e. >>>> remove all elements from it? >>>> thanks >>>> Slobodan >>> ? (setf v (make-array 0 :element-type 'string :fill-pointer 0 >>> :adjustable t)) >>> #() >>> ? (dotimes (i 10) (vector-push-extend i v)) >>> ;Compiler warnings : >>> ; In an anonymous lambda form at position 16: Undeclared free variable >>> V >>> NIL >>> ? v >>> #(0 1 2 3 4 5 6 7 8 9) >>> ? (setf (fill-pointer v) 0) >>> 0 >>> ? v >>> #() >>> ? >> I've thought about that but does just setf-ing the fill pointer >> releases the storage space? >> >> Slobodan > > CL> (setf v (make-array 0 :element-type 'string :fill-pointer 0 > :adjustable t)) > #() > CL> (dotimes (i 10) (vector-push-extend i v)) > > NIL > CL> (array-dimensions v) > (15) > CL> (setf (fill-pointer v) 0) > 0 > CL> (array-dimensions v) > (15) > > > To answer my own questions at least on sbcl answer is no. > > Slobodan Ah, my other post isn't as useful for you then. You're probably looking for ADJUST-ARRAY. CL-USER 29 > *v* #() CL-USER 30 > (array-total-size *v*) 16 CL-USER 31 > (adjust-array *v* 0) #() CL-USER 32 > (array-total-size *v*) 0 //JT
From: Slobodan Blazeski on 6 Mar 2010 13:28 On Mar 6, 7:26 pm, Joshua Taylor <tay...(a)cs.rpi.edu> wrote: > Slobodan Blazeski wrote: > > On Mar 6, 7:14 pm, Slobodan Blazeski <slobodan.blaze...(a)gmail.com> > > wrote: > >> On Mar 6, 7:09 pm, Ron Garret <rNOSPA...(a)flownet.com> wrote: > > >>> In article > >>> <7d69ae1c-2467-4298-974e-6fc98e646...(a)t23g2000yqt.googlegroups.com>, > >>> Slobodan Blazeski <slobodan.blaze...(a)gmail.com> wrote: > >>>> I have an array defined as: > >>>> (make-array 0 :element-type 'string :fill-pointer 0 > >>>> :adjustable t) > >>>> After adding some elements I want to know how to clear it , i.e. > >>>> remove all elements from it? > >>>> thanks > >>>> Slobodan > >>> ? (setf v (make-array 0 :element-type 'string :fill-pointer 0 > >>> :adjustable t)) > >>> #() > >>> ? (dotimes (i 10) (vector-push-extend i v)) > >>> ;Compiler warnings : > >>> ; In an anonymous lambda form at position 16: Undeclared free variable > >>> V > >>> NIL > >>> ? v > >>> #(0 1 2 3 4 5 6 7 8 9) > >>> ? (setf (fill-pointer v) 0) > >>> 0 > >>> ? v > >>> #() > >>> ? > >> I've thought about that but does just setf-ing the fill pointer > >> releases the storage space? > > >> Slobodan > > > CL> (setf v (make-array 0 :element-type 'string :fill-pointer 0 > > :adjustable t)) > > #() > > CL> (dotimes (i 10) (vector-push-extend i v)) > > > NIL > > CL> (array-dimensions v) > > (15) > > CL> (setf (fill-pointer v) 0) > > 0 > > CL> (array-dimensions v) > > (15) > > > To answer my own questions at least on sbcl answer is no. > > > Slobodan > > Ah, my other post isn't as useful for you then. You're probably looking > for ADJUST-ARRAY. > > CL-USER 29 > *v* > #() > > CL-USER 30 > (array-total-size *v*) > 16 > > CL-USER 31 > (adjust-array *v* 0) > #() > > CL-USER 32 > (array-total-size *v*) > 0 > > //JT That's exactly what I was looking for. thanks Slobodan
From: Joshua Taylor on 6 Mar 2010 13:31 Slobodan Blazeski wrote: > On Mar 6, 7:26 pm, Joshua Taylor <tay...(a)cs.rpi.edu> wrote: >> Slobodan Blazeski wrote: >>> On Mar 6, 7:14 pm, Slobodan Blazeski <slobodan.blaze...(a)gmail.com> >>> wrote: >>>> On Mar 6, 7:09 pm, Ron Garret <rNOSPA...(a)flownet.com> wrote: >>>>> In article >>>>> <7d69ae1c-2467-4298-974e-6fc98e646...(a)t23g2000yqt.googlegroups.com>, >>>>> Slobodan Blazeski <slobodan.blaze...(a)gmail.com> wrote: >>>>>> I have an array defined as: >>>>>> (make-array 0 :element-type 'string :fill-pointer 0 >>>>>> :adjustable t) >>>>>> After adding some elements I want to know how to clear it , i.e. >>>>>> remove all elements from it? >>>>>> thanks >>>>>> Slobodan >>>>> ? (setf v (make-array 0 :element-type 'string :fill-pointer 0 >>>>> :adjustable t)) >>>>> #() >>>>> ? (dotimes (i 10) (vector-push-extend i v)) >>>>> ;Compiler warnings : >>>>> ; In an anonymous lambda form at position 16: Undeclared free variable >>>>> V >>>>> NIL >>>>> ? v >>>>> #(0 1 2 3 4 5 6 7 8 9) >>>>> ? (setf (fill-pointer v) 0) >>>>> 0 >>>>> ? v >>>>> #() >>>>> ? >>>> I've thought about that but does just setf-ing the fill pointer >>>> releases the storage space? >>>> Slobodan >>> CL> (setf v (make-array 0 :element-type 'string :fill-pointer 0 >>> :adjustable t)) >>> #() >>> CL> (dotimes (i 10) (vector-push-extend i v)) >>> NIL >>> CL> (array-dimensions v) >>> (15) >>> CL> (setf (fill-pointer v) 0) >>> 0 >>> CL> (array-dimensions v) >>> (15) >>> To answer my own questions at least on sbcl answer is no. >>> Slobodan >> Ah, my other post isn't as useful for you then. You're probably looking >> for ADJUST-ARRAY. >> >> CL-USER 29 > *v* >> #() >> >> CL-USER 30 > (array-total-size *v*) >> 16 >> >> CL-USER 31 > (adjust-array *v* 0) >> #() >> >> CL-USER 32 > (array-total-size *v*) >> 0 >> >> //JT > That's exactly what I was looking for. > > thanks > Slobodan Glad it helps. I also realized that if you use ADJUST-ARRAY without changing the fill-pointer first, you'll want to give the fill-pointer argument to adjust-array, too. E.g., see the error in the following (and the fixed call immediately following it): CL-USER > *v* #(0 1 2 3 4 5 6 7 8 9) CL-USER > (adjust-array *v* 0) Error: 10 is an illegal fill-pointer. 1 (abort) Return to level 0. 2 Return to top loop level 0. Type :b for backtrace or :c <option number> to proceed. Type :bug-form "<subject>" for a bug report template or :? for other options. CL-USER : 1 > :a CL-USER > (adjust-array *v* 0 :fill-pointer 0) #()
From: Pascal Costanza on 7 Mar 2010 06:48 On 06/03/2010 19:23, Joshua Taylor wrote: > Ron Garret wrote: >> In article >> <7d69ae1c-2467-4298-974e-6fc98e6460b6(a)t23g2000yqt.googlegroups.com>, >> Slobodan Blazeski <slobodan.blazeski(a)gmail.com> wrote: > >> [...] >>> After adding some elements I want to know how to clear it , i.e. >>> remove all elements from it? > > [...] >> ? (setf (fill-pointer v) 0) >> 0 >> ? v >> #() >> ? > > Two things to be aware of are (i) that changing the fill pointer doesn't > deallocate the memory used by the vector (which probably doesn't matter > all that much) and (ii) there are still references to the elements in > places past the fill pointer: > > > CL-USER > > (defparameter *v* (make-array 0 :fill-pointer 0 :adjustable t > :initial-element 0)) > *V* > > CL-USER > > (dotimes (i 10) > (vector-push-extend i *v*)) > NIL > > CL-USER 12 > (aref *v* 5) > 5 > > CL-USER 13 > > (setf (fill-pointer *v*) 0) > 0 > > CL-USER 14 > > (aref *v* 5) > 5 > > > This can keep objects from being garbage collected in situations where > you might have expected them to be (after all you did say "/remove/ all > elements from it", not just "make the vector have length 0 again". As > such, it's not a bad idea to set the array contents to NIL (or whatever > you like) before setting the fill pointer to 0. E.g., > > > CL-USER > > (dotimes (i 10) > (vector-push-extend i *v*)) > NIL > > CL-USER > > *v* > #(0 1 2 3 4 5 6 7 8 9) > > CL-USER > > (map-into *v* (constantly nil)) > #(NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL) (fill *v* nil) is probably better. Pascal -- My website: http://p-cos.net Common Lisp Document Repository: http://cdr.eurolisp.org Closer to MOP & ContextL: http://common-lisp.net/project/closer/
From: Joshua Taylor on 7 Mar 2010 14:33
Pascal Costanza wrote: > On 06/03/2010 19:23, Joshua Taylor wrote: >> CL-USER > >> (map-into *v* (constantly nil)) >> #(NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL) > > (fill *v* nil) is probably better. Much better indeed---good catch! |