I noticed that when using remove,remove-if etc. functions on an adjustable array or an array with a fill-pointer, the result is an array _without_ a fill-pointer and that is not adjustable.
Why is this?
And is there a way to remove elements from (the interior of a) fill-pointer array and still have a fill-pointer array as the result without defining a new fill-pointer-remove-if function or redefining remove-if etc. ?
> I noticed that when using remove,remove-if etc. functions on an > adjustable array or an array with a fill-pointer, the result is an > array _without_ a fill-pointer and that is not adjustable.
> Why is this?
Because the standard requires it:
Section 17.1:
"A sequence function is a function defined by this specification or added as an extension by the implementation that operates on one or more sequences. Whenever a sequence function must construct and return a new vector, it always returns a simple vector. Similarly, any strings constructed will be simple strings."
I wrote: >> I noticed that when using remove,remove-if etc. functions on an >> adjustable array or an array with a fill-pointer, the result is an >> array _without_ a fill-pointer and that is not adjustable.
>> Why is this?
> Because the standard requires it:
Atually, this isn't right. It's possible that arrays with fill pointers or adjustable arrays are also simple, but they typically aren't in Lisps implemented on stock hardware.
* joac...@arti.vub.ac.be | I noticed that when using remove,remove-if etc. functions on an | adjustable array or an array with a fill-pointer, the result is an array | _without_ a fill-pointer and that is not adjustable. | | Why is this?
Because you ask for a new sequence with the `removeŽ version.
Perhaps you should investigate the `deleteŽ versions?
-- Erik Naggum, Oslo, Norway
Act from reason, and failure makes you rethink and study harder. Act from faith, and failure makes you blame someone and push harder.
* joachim wrote: > "What are fill-pointer arrays for if you can only implement a stack > with them and not e.g. remove elements?"
Well, the classic answer would be some kind of buffer object. Say I'm reading chunks of data into a buffer, and I don't know how big they are, but I know there's some maximum size (or maybe, if the size is bigger than I've allowed for I'm willing to use ADJUST-ARRAY to allocate a bigger buffer). I want to reuse the buffer, but I don't want to have to keep passing around the information that only the first n elements of this thing actually have useful data. So I use a fill pointer to tell me that.
However, going back to your original question, I think you may be confused about what REMOVE &co do - they are nondestructive functions, so they aren't allowed to alter the arrays that are their arguments. DELETE &co are allowed to be destructive, but don't have to be so.
