On Thu, 6 May 2010, spir ☣ wrote:
Hello,
Where can one find information on types like dynamic array? Also, on funcs
or procs that apply on them, like setLength & copy. If the answers to the
following questions are somewhere, just tell me...
* Can one rely on the fact that setLength keeps existing data (in the range of
the new size), both when up- and down-sizing? Or do my trials work only because
the pointed memory has not yet been overwritten?
Yes, one can rely on this.
* How is resizing actually performed (is the data moved to a newly allocated
area)?
This is an implementation detail which should be of no concern to the user.
* Does copy onto a dynamic array automatically resize (setLength), even if the
target is greater than needed? (I would like no.)
* Can one set the first index where to copy on the target array? (eg to join 2
arrays into a greater one, or to extend an existing one that has free space at
tail)
* Can one use copy from/to a *static* array? (If no, why not?)
What does 'copy onto' mean in these questions ?
* What other differences with static array, if any? (Aside the fact that one
does not need to explicitely reallocate and copy on resizing.)
A dynamic array is reference counted.
Thus
A:=B;
Does not actually copy the entire array, it just lets B point to the same
memory area where the array data is stored and increases the reference count.
With static arrays
A:=B;
Will actually create a copy.
For Christmas:
* Can one add or remove an element --at the end? (And have the array behave
accordingly.)
No.
* Can one add or remove an element --anywhere? (And have the array behave
accordingly.)
No.
If the answers to last 2 questions is "only every 29th of februar", how
can one have a "flexible" array? Is there something like that in stock?
Would you implement it on top of dynamic array, or rather from scratch on
top of static array (since the "dynamicity" does not seem very helpful)?
If you want a flexible array, use TList or TFPList or TCollection from the
classes unit.
Michael.
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