Slices in Pascal

program Slices;

uses
  SysUtils;

type
  TStringArray = array of string;

procedure PrintArray(const arr: TStringArray; const prefix: string);
var
  i: Integer;
begin
  Write(prefix, ' [');
  for i := Low(arr) to High(arr) do
  begin
    if i > Low(arr) then
      Write(' ');
    Write(arr[i]);
  end;
  WriteLn(']');
end;

var
  s: TStringArray;
  c: TStringArray;
  l: TStringArray;
  t: TStringArray;
  twoD: array of TStringArray;
  i, j: Integer;

begin
  // Dynamic arrays in Pascal are similar to slices in concept.
  // An uninitialized dynamic array is empty and has length 0.
  WriteLn('uninit: ', Length(s) = 0);

  // To create an empty dynamic array with non-zero length, use SetLength.
  SetLength(s, 3);
  PrintArray(s, 'emp:');
  WriteLn('len: ', Length(s), ' cap: ', Length(s));

  // We can set and get elements just like with regular arrays.
  s[0] := 'a';
  s[1] := 'b';
  s[2] := 'c';
  PrintArray(s, 'set:');
  WriteLn('get: ', s[2]);

  // Length returns the length of the dynamic array as expected.
  WriteLn('len: ', Length(s));

  // To add elements to a dynamic array, we can use SetLength
  // and then assign values to the new elements.
  SetLength(s, Length(s) + 1);
  s[High(s)] := 'd';
  SetLength(s, Length(s) + 2);
  s[High(s) - 1] := 'e';
  s[High(s)] := 'f';
  PrintArray(s, 'apd:');

  // To copy a dynamic array, we can use the Copy function.
  c := Copy(s);
  PrintArray(c, 'cpy:');

  // Pascal doesn't have a built-in slice operator, but we can
  // use Copy to achieve similar functionality.
  l := Copy(s, 2, 3);
  PrintArray(l, 'sl1:');

  l := Copy(s, 0, 5);
  PrintArray(l, 'sl2:');

  l := Copy(s, 2, Length(s) - 2);
  PrintArray(l, 'sl3:');

  // We can declare and initialize a dynamic array in a single line.
  t := TStringArray.Create('g', 'h', 'i');
  PrintArray(t, 'dcl:');

  // Pascal doesn't have a built-in equality function for arrays,
  // so we'd need to implement our own if needed.

  // Dynamic arrays can be used to create multi-dimensional structures.
  SetLength(twoD, 3);
  for i := 0 to 2 do
  begin
    SetLength(twoD[i], i + 1);
    for j := 0 to i do
      twoD[i][j] := IntToStr(i + j);
  end;

  Write('2d: [');
  for i := 0 to 2 do
  begin
    if i > 0 then
      Write(' ');
    PrintArray(twoD[i], '');
  end;
  WriteLn(']');
end.

This Pascal code demonstrates concepts similar to Go’s slices using dynamic arrays. Here are some key points:

Pascal uses dynamic arrays (array of Type) which are similar to slices in Go.
SetLength is used to create or resize dynamic arrays, similar to make in Go.
Pascal doesn’t have a built-in append function, so we manually resize the array and assign new values.
The Copy function in Pascal can be used to achieve functionality similar to Go’s slice operations.
Pascal doesn’t have a built-in way to compare arrays for equality, so you’d need to implement this yourself if needed.
Multi-dimensional dynamic arrays are possible in Pascal, similar to slices of slices in Go.

Note that Pascal’s dynamic arrays are not exactly the same as Go’s slices in terms of underlying implementation and performance characteristics, but they serve a similar purpose in providing dynamically-sized array-like structures.

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Slices in Pascal