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Languages :: Pascal :: array deletion
By: digitaltree U.S.A.  Date: 26/04/2003 00:00:00  English  Points: 25 Status: Answered
Quality : Excellent
hi
I need this program to do multiple deletions but its only doing one .
what do I need to do with the procedure purge?



PROGRAM SortingofArray;

Const
amax = 12;

TYPE
ArrayIndex = 1..amax;
LetterList = RECORD
count: 0..amax;
alpha: ARRAY[ArrayIndex] OF char;
END;
VAR
F :LetterList ; n: integer; m:char;

PROCEDURE LoadArray( var C : LetterList; x: integer);
var Index: ArrayIndex;
BEGIN
writeln ('Enter ',x, ' characters:');
with C DO BEGIN
Count := x;
FOR Index := 1 to Count DO
readln(alpha[Index]);
writeln;
END; END;

PROCEDURE PrintArray( D:LetterList );
VAR
i: integer; Index: ArrayIndex;
BEGIN
with D DO BEGIN
writeln('Count: ',count);
write(' ');
FOR i :=1 TO amax DO
write(i:4);
writeln;
write('alpha ');
FOR Index := 1 TO Count DO
write(alpha[Index]:4);
writeln;
END; END;

PROCEDURE Purge(var Letters: LetterList; ToPurge: char);
var
i ,k : integer; Index: ArrayIndex;

begin
k:=0;
with Letters DO BEGIN
For index := 1 to count do
if alpha[index] = ToPurge then
begin
k:=k+1;
For index := index to count do
alpha[index]:=alpha[index+k]; end;
Count:=Count-k;
END; End;

BEGIN
Writeln ('Enter number of character that would be loaded: ');
readln(n);
LoadArray(F,n);
PrintArray(F);
writeln;
write('Enter letter to purge: ');
readln(m);
Purge(F,m);
PrintArray(F);
readln;
End.
By: VGR Date: 26/04/2003 17:07:00 English  Type : Comment
that's because when you suppress a charcater, count computed at the beginnign of the loop has stayed the same and gets incremented, while the deletion wxould have suggested to treat again the character of the same index.

I hope I'm clear.

the loop is badly written with a for, given :
-count of the for varies during iteration
-you use for index:=index to ... something that is not encouraged

do you want it rewritten ?
By: VGR Date: 26/04/2003 17:15:00 English  Type : Answer
here it is :

-------------------- results
Enter number of character that would be loaded:
5
Enter 5 characters:
A
B
B
C
B

Count: 5
1 2 3 4 5 6 7 8 9 10 11 12
alpha A B B C B

Enter letter to purge: B
Count: 2
1 2 3 4 5 6 7 8 9 10 11 12
alpha A C


------------------ source code
PROCEDURE Purge(var Letters: LetterList; ToPurge: char);
var i ,k : integer; Index, index2: ArrayIndex;

begin
index:=1;
With Letters Do
While (index<=count) Do
Begin
if alpha[index] = ToPurge then
begin
For index2 := index to count do alpha[index2]:=alpha[index2+1];
Dec(count);
end { For }
Else Inc(index);
End; { While, With }
End; { Purge Procedure }
By: VGR Date: 26/04/2003 17:16:00 English  Type : Comment
the "{ For }" in line "end { For }" is an old comment I had put in your code. Ignore it.

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