According documentation a proper use of the Adel() function, is:
ADEL(<aTarget>, <nPosition>) --> aTarget
where <nPosition> is the <aTarget> array element being deleted.
However, function ADEL() does interesting, -yet unexpected at least for
me, things when it's invoked with a "slightly fuzzy" way shown in the
sample below:
8<---------------------------------------------------------------------------------
#define CRLF HB_OSNewLine()
PROCEDURE MAIN()
LOCAL aArray := {"one", "two", "three", "four", "five"}
? "TestProg: " + HB_ARGV()+ " [testing adel() function]"
?
"============================================================================"
?
? "--- Our array before adel()'s touch.. --> "
AEVAL( aArray, {|ele| QQOUT(HB_ValToExp(ele) + " ")} )
?
? "CASE_1 : ADEL(aArray, .T. .OR. .F.) --> "
ADEL(aArray, .T. .OR. .F.) // to adel() or to not adel()?
AEVAL( aArray, {|ele| QQOUT(HB_ValToExp(ele) + " ")} )
?
? "CASE_2 : ADEL(aArray, 'Guess what element you'll nullify* now?') --> "
ADEL(aArray, "Guess what element you'll nullify now?") // RTFM
AEVAL( aArray, {|ele| QQOUT(HB_ValToExp(ele) + " ")} )
?
? "CASE_3 : ADEL(aArray, 2^66) --> "
ADEL(aArray, 2^66) // can arrays grow up so much ??
AEVAL( aArray, {|ele| QQOUT(HB_ValToExp(ele) + " ")} )
?
? "CASE_4 : ADEL(aArray) --> "
ADEL(aArray) // do you mean, delete entire array?
AEVAL( aArray, {|ele| QQOUT(HB_ValToExp(ele) + " ")} )
?
? "CASE_4b : ADEL(ADEL(aArray)) --> "
?? ADEL(ADEL(aArray)) // now that you've learned the art of adeleting...
?
AEVAL( aArray, {|ele| QQOUT(HB_ValToExp(ele) + " ")} )
?
Wait
RETURN
--------------------------------------------------------------------------------->8
In cases 1 & 2 one would expect the runtime mechanism to throw an error
because of the erroneous value types passed.
In case 3 a "boundary error" might be more appropriate/alarming.
And in Case 4 either:
- an entire array deletion could be more connotative expected or
- a runtime error due to lack of the 2nd mandatory arg.
Having the Adel() in all the above case to delete the first array
element is quite unreasonable, primarily because such an action is
undocumented. To be fair this is not a Harbour only "feature". Clipper
behaves exactly the same here!
And while talking about adel() i think the name ADEL is rather
misleading, since the function does NOT actually delete elements,
but rather nullifies them, and you have to use asize()[*] to achieve
what you probably wanted to do. Perhaps ANUL() would be a more precise name
but i think it's a little late now to rename it <g>.
__________________________________________________________________
[*] I am aware of HB_ADEL() function, that accepts a 3rd parameter
(boolean) by which you can eventually "adjust" the array size without
the need of calling asize(). This is a good thing. The "bad" things are
that HB_adel() stands in the shade of adel() (due to lack of
documentation) while the above remarks about ADEL() apply also for
HB_ADEL too.
---
Pete
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