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I have a code written in Pascal. I have a record type called recordPembeli and I have an array[1..x] of recordPembeli. The x in this array will be the length of the data which the user determines in the body of program readln(x).

Here is the program:

program iniSesiDua;
uses crt;

type
    recordPembeli = record
        nama : string[5];
        jumlahPembelian : integer;
    end;

var
    x : integer
    dataPembelian : array[1..x] of recordPembeli;

begin
    clrscr;

    write('Masukkan jumlah pembeli : ');readln(x);

    readln;

end.

I try it and it says :

Warning: Variable "x" does not seem to be initialized

Error: Can't evaluate constant expression

Can I even determine the length of the data by user input in array of record or is it forbidden?

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3 Answers 3

Reset to default
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Can I even determine the length of the data by user input in array of records...?

Yes you can, but the array must be dynamic, which means that the number of elements is not defined at compile time, but at run time:

var
  x: integer;
  dataPembelian: array of recordPembeli; // dynamic array, no size
  
begin
  write('Masukkan jumlah pembeli : ');readln(x); // Get length from user
  SetLength(dataPembelian, x);                   // create the records in the array

Note that the indexing of the array elements starts from 0.

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1 Comment

Oh, I see. So there's a method called SetLength to set the length of the array and first I need to declare the array as a dynamic array. Thank you! ^^
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The bounds of an array (unless it is a dynamic array) must be a compile time constant.

You are using a variable, and one that hasn't been initialized at that.

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Sorry, I don't know if there is a dynamic array before. Thank you! ^^
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The variable determining the length x and the array’s declaration cannot be in the same block. You will need to use a nested block like this:

program iniSesiDua(input, output);
    type
        recordPembeli = record
                nama: string(5);
                jumlahPembelian: integer;
            end;
    
    var
        x: integer;
    
    procedure readAndProcessPembelin;
    var
        dataPembelian: array[1..x] of recordPembeli;
    begin
        { You read and process data here. }
    end;
    
    { === MAIN =============================================== }
    begin
        write('Masukkan jumlah pembeli : ');
        readLn(x);
        readAndProcessPembelin
    end.

Non-constant subrange bounds are an extension of ISO standard 10206 “Extended Pascal”. Your error messages seem like to have been emitted by the FPC (Free Pascal Compiler). This processor does not support Extended Pascal (yet). There you are forced to use an alternative data type, e. g. a linked list or more conveniently “dynamic” arrays.

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2 Comments

So there's 2 solution, right? The first is to create a Procedure and put my code in it and the second is to use a dynamic array. Thank you! ^^
There are several solutions. The important thing here is to grasp that x and your array[1..x] of recordPembeli cannot be in the same block (in var sections belonging to one begin…end), because the compiler cannot decide yet how much space, how much memory dataPembelian is supposed to occupy. Once you define x, i. e. make an assignment via readLn, it becomes possible to say how large an array[1..x] of recordPembeli will be. The/A standard method is shown above, yet in Delphi/Free Pascal you will need to explicitly announce this using setLength with “dynamic arrays”.

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