Array not reading elements

[Sukuna]

Hello,
I am experimenting with this https://castle-engine.io/modern_pascal guide to modern Pascal. I am not happy with it by the way and am searching for other online material on Pascal, should be a tutorial.

When I write elements for my array they are not squared, instead the numbers from 1 to 10 are squared.

Code: Pascal  [Select][+][-]

1. program Project1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. uses
6.   {$IFDEF UNIX}
7.   cthreads,
8.   {$ENDIF}
9.   Classes
10.   { you can add units after this };
11.             var
12.               x:integer;
13.                 MyArray:array[1..10]of integer = (88,82,89,80,29,20,28,21,22,20);
14. begin
15.  
16.  
17.   for x:=1 to 10 do
18.   begin
19.     MyArray[x] := x*x;
20.     writeln('Square of array elements is: ',MyArray[x]);
21.   end;
22.  
23.   for x:= Low(MyArray) to High(MyArray) do
24.   writeln('Square is: ',MyArray[x]);
25.   readln;
26. end.
27.  

[Thaddy]

Try:

Code: Pascal  [Select][+][-]

1. {$mode objfpc}
2. var
3.   x:integer;
4.   MyArray:array[1..10]of integer = (88,82,89,80,29,20,28,21,22,20);
5. begin
6.  
7.  
8.   for x in myarray do
9.   begin
10.     MyArray[x] := x*x;
11.       writeln('Square of array elements is: ',MyArray[x]);
12.   end;
13.  
14.   for x in myarray do
15.     writeln('Square is: ',MyArray[x]);
16.   readln;
17. end.

The reason is that x has double meaning in your code.
In my example x has single meaning, the value, not the value AND the index! It is also "Modern Pascal".

(The modern pascal guide you refer to has only one really big flaw: a complete misunderstanding of interfaces and the differences between COM and CORBA, ignore that chapter, it is a known shortcoming, there are better guides, many)

[Martin_fr]

Code: Pascal  [Select][+][-]

1.   MyArray[x] := x*x;

Squares "x", which in the original code is 1 to 10

Code: Pascal  [Select][+][-]

1.   for x:=1 to 10 do

Should be

Code: Pascal  [Select][+][-]

1.   MyArray[x] := MyArray[x]*MyArray[x];

[Nimbus]

Or

Code: Pascal  [Select][+][-]

1. MyArray[x] := Sqr(MyArray[x]);

as the System unit has built-in function for squaring numbers
https://www.freepascal.org/docs-html/rtl/system/sqr.html

[Sukuna]

Try:

Code: Pascal  [Select][+][-]

1. {$mode objfpc}
2. var
3.   x:integer;
4.   MyArray:array[1..10]of integer = (88,82,89,80,29,20,28,21,22,20);
5. begin
6.  
7.  
8.   for x in myarray do
9.   begin
10.     MyArray[x] := x*x;
11.       writeln('Square of array elements is: ',MyArray[x]);
12.   end;
13.  
14.   for x in myarray do
15.     writeln('Square is: ',MyArray[x]);
16.   readln;
17. end.

The reason is that x has double meaning in your code.
In my example x has single meaning, the value, not the value AND the index! It is also "Modern Pascal".

(The modern pascal guide you refer to has only one really big flaw: a complete misunderstanding of interfaces and the differences between COM and CORBA, ignore that chapter, it is a known shortcoming, there are better guides, many)

Could you mention the other guides?

[Sukuna]

Code: Pascal  [Select][+][-]

1.   MyArray[x] := x*x;

Squares "x", which in the original code is 1 to 10

Code: Pascal  [Select][+][-]

1.   for x:=1 to 10 do

Should be

Code: Pascal  [Select][+][-]

1.   MyArray[x] := MyArray[x]*MyArray[x];

Thank you, I understood this now.

[Sukuna]

I have another issue now. The first for - to loop gives just the highest number squared, not all 10 elements.
If I use this code only 9801 is printed on the console for the first loop, the second one prints all 10. How could I change this?

Code: Pascal  [Select][+][-]

1. rogram Project1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. uses
6.   {$IFDEF UNIX}
7.   cthreads,
8.   {$ENDIF}
9.   Classes
10.   { you can add units after this };
11.  
12. var
13.   x:integer;
14.  
15.   MyArray : array[1..10] of integer = (88,89,80,82,20,29,28,22,90,99);
16. begin
17.  
18.   for x := 1 to 10 do
19.   MyArray[x] := MyArray[x]*MyArray[x];
20.   writeln('The number squared is: ',MyArray[x]);
21.  
22.   for x := Low(MyArray) to High(MyArray) do
23.   writeln('The number squared is: ',MyArray[x]);
24.  
25.   readln;
26. end.  

[Khrys]

You need to use  begin  and  end  to group multiple statements together:

Code: Pascal  [Select][+][-]

1. for x := 1 to 10 do begin
2.   MyArray[x] := MyArray[x]*MyArray[x];
3.   writeln('The number squared is: ',MyArray[x]);
4. end;