hp prime - programming with lists

[giancarlo]

Hello,
Today i was playing with lists in programs and in particular list of strings. Please tell me if i am wrong with explorations.

1) sort(list) doesn't work with strings. Items are unchanged after 'sort'. 'Sort' does work with numbers.

2) i am not able to delete an item of a list in my program. I was trying to remove a string from a list in vain. Since i wasn't able to remove it, i assigned an empty value "" to it. Do you know which command there is to remove an item from a list? I could write a program to do it in case it doesn't exist.

3) i read somewhere in this forum that the way to assign a string to a variable via a Input() command was to define the variable and assign a value to it like:
local X2:="";
input (x2, "my title","my variable");
The result is not very useful. I can see an empty string into the variable entry field but i cannot use it because i edit the command line so i have to manually add the string "" and then entry my text.

4) I defined an input() of a string in a "repeat... until..." loop. When i run into this loop the first time i can entry the string but starting from the second loop, when i see the input screen of the string, i can still see the value i entered during the first run. Did you encouter the same issue?

Thanks

Giancarlo

P.s. please answers to my points referring to the point numbers i indicated. The reading will be easier.

[Marcus von Cube, Germany]

ad 2: remove(what,list) removes the item 'what' from a list. To be precise, 'what' is either a boolean function to identify list items to remove or the value to remove. 'what' is not the position! A workaround could be to replace the item in question by a special value and then use remove() to remove all occurrences of the marker from the list.

[Patrice]

1+2) Here is a couple utilities about list handling in a programming point of view. The name come from the language Clipper (xBase)

with examples at the end

EXPORT AAdd(Lst, Val_)  // add element at end of list

BEGIN

RETURN CONCAT(Lst, {Val_});

END;

EXPORT AIns(Lst, Pos_, Val_)  // insert element in list

BEGIN

IF Pos_ == 1 THEN RETURN CONCAT({Val_}, Lst); END;

IF Pos_ > SIZE(Lst) THEN RETURN CONCAT(Lst, {Val_}); END;

RETURN CONCAT(CONCAT(Sub(Lst, 1, Pos_-1), {Val_}), Sub(Lst, Pos_, (SIZE(Lst))));

END;

EXPORT ADel(Lst, Pos_)  // delete element of list

BEGIN

LOCAL Tmp;

IF Pos_ == 1 THEN

  IF SIZE(Lst) == 1 THEN Tmp:= {};

  ELSE Tmp:= SUB(Lst,2,SIZE(Lst)); END;

ELSE

  IF Pos_ == SIZE(Lst) THEN Tmp:= SUB(Lst,1,SIZE(Lst)-1);

  ELSE Tmp:= CONCAT(Sub(Lst, 1, Pos_-1), Sub(Lst, Pos_+1, (SIZE(Lst))));

  END;

END;

RETURN Tmp;

END;

EXPORT ADelTail(Lst)  // delete last element of list

BEGIN

IF SIZE(Lst) == 1 THEN RETURN {};

ELSE RETURN SUB(Lst,1,SIZE(Lst)-1); END;

END;

EXPORT ASize(Lst, NewSize)  // resize list

BEGIN

LOCAL Tmp;

IF NewSize == 0 THEN Tmp:= {}; END;

IF SIZE(Lst) > NewSize THEN Tmp:= SUB(Lst,1, NewSize); END;

IF SIZE(Lst) == NewSize THEN Tmp:= Lst; END;

IF SIZE(Lst) < NewSize THEN Tmp:= CONCAT(Lst, MAKELIST(0, A, SIZE(Lst)+1, NewSize)); END;

RETURN Tmp;

END;

EXPORT ATail(Lst)  // Last element of list

BEGIN

RETURN Lst(SIZE(Lst));

END;

EXPORT ASort(Lst, Col)  // Sort a list of lists

BEGIN

LOCAL Scan, Tmp, Pos, Db, Fn, Ml;

IF SIZE(Lst) > 0 THEN

  Tmp:= {Lst(1)};

  FOR Scan FROM 2 TO SIZE(Lst) DO

    IF Lst(Scan,Col) < Tmp(1,Col) THEN Tmp:= AIns(Tmp, 1, Lst(Scan)); ELSE

      IF Lst(Scan,Col) >= Tmp(SIZE(Tmp),Col) THEN Tmp:= AAdd(Tmp, Lst(Scan)); ELSE

        Db:= 2; Fn:= SIZE(Tmp)-1;

        WHILE Db <= Fn DO

          Ml:= IP((Db+Fn)/2);

          IF Tmp(Ml,Col) <= Lst(Scan,Col) THEN Db:= Ml+1;

          ELSE Fn:= Ml-1; END;

        END;

        Tmp:= AIns(Tmp, Db, Lst(Scan));

      END;

    END;

  END;

ELSE

  Tmp:= {};

END;

RETURN Tmp;

END;

EXPORT TestList()

BEGIN

LOCAL Cnt, List;

List:= {};

FOR Cnt FROM 1 TO 15 DO

  List:= AAdd(List, Cnt);

  MSGBOX(ATail(List)+":"+STRING(List));

END;

List:= MAKELIST(A, A, 1, 15, 1);

FOR Cnt FROM 1 TO 15 DO

  List:= ADel(List, 1);

  MSGBOX(List);

END;

List:= MAKELIST(A, A, 1, 15, 1);

FOR Cnt FROM 1 TO 10 DO

  List:= ADel(List, 3);

  MSGBOX(List);

END;

List:= MAKELIST(A, A, 1, 15, 1);

FOR Cnt FROM 1 TO 15 DO

  List:= ADelTail(List);

  MSGBOX(List);

END;

END;

[giancarlo]

Hello Markus and Patrice,
Thank you very much for your answer. I am goign to work on this today and let you know the result(s).

Regarding point 4). Running a loop with an input() command in it is obvious that the local variable maintain the last value entered at each iteration of the loop. Anyway i solved the issue, assigning a "" value at the end of each iteration.

At this point only question 3 remains unsolved. Any idea on how to input() a string in a clean way? This is what i tried:

EXPORT PROVA()
BEGIN

LOCAL X1:="";
INPUT(X1,"titolo","stringa: ");

END

As said at the first post of this thread, i assigned to my local variable an empty string "". When i execute the program, i can see the two "" in the variable entry field at the top of the screen but i use the command line to fill my data and i have to write my string in brackets again.
At this point there is no need to preassign a string if you can't use its predefined brakets ("").

Thanks for any hint in this field.

Giancarlo from cappuccino state