Data commit

Task/Array-concatenation/Delphi/array-concatenation-1.delphi

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+// This example works on stuff as old as Delphi 5 (maybe older)
+// Modern Delphi / Object Pascal has both
+//   • generic types
+//   • the ability to concatenate arrays with the '+' operator
+// So I could just say:
+//   myarray := [1] + [2, 3];
+// But if you do not have access to the latest/greatest, then:
+{$apptype console}
+
+type
+  // Array types must be declared in order to return them from functions
+  // They can also be used with open array parameters.
+  TArrayOfString = array of string;
+
+function Concat( a, b : array of string ): TArrayOfString; overload;
+{
+  Every array type needs its own 'Concat' function:
+    function Concat( a, b : array of integer ): TArrayOfInteger; overload;
+    function Concat( a, b : array of double  ): TArrayOfDouble;  overload;
+    etc
+  Also, dynamic and open array types ALWAYS start at 0. No need to complicate indexing here.
+}
+var
+  n : Integer;
+begin
+  SetLength( result, Length(a)+Length(b) );
+  for n := 0 to High(a) do result[          n] := a[n];
+  for n := 0 to High(b) do result[Length(a)+n] := b[n]
+end;
+
+// Example time!
+function Join( a : array of string; sep : string = ' ' ): string;
+var
+  n : integer;
+begin
+  if Length(a) > 0 then result := a[0];
+  for n := 1 to High(a) do result := result + sep + a[n]
+end;
+
+var
+  names : TArrayOfString;
+begin
+  // Here we use the open array parameter constructor as a convenience
+  names := Concat( ['Korra', 'Asami'], ['Bolin', 'Mako'] );
+  WriteLn( Join(names) );
+
+  // Also convenient: open array parameters are assignment-compatible with our array type!
+  names := Concat( names, ['Varrick', 'Zhu Li'] );
+  WriteLn( #13#10, Join(names, ', ') );
+
+  names := Concat( ['Tenzin'], names );
+  Writeln( #13#10, Join(names, #13#10 ) );
+end.

Task/Array-concatenation/Delphi/array-concatenation-2.delphi

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+type
+  TReturnArray = array of integer; //you need to define a type to be able to return it
+
+function ConcatArray(a1,a2:array of integer):TReturnArray;
+var
+  i,r:integer;
+begin
+  { Low(array) is not necessarily 0 }
+  SetLength(result,High(a1)-Low(a1)+High(a2)-Low(a2)+2); //BAD idea to set a length you won't release, just to show the idea!
+  r:=0; //index on the result may be different to indexes on the sources
+  for i := Low(a1) to High(a1) do begin
+    result[r] := a1[i];
+    Inc(r);
+  end;
+  for i := Low(a2) to High(a2) do begin
+    result[r] := a2[i];
+    Inc(r);
+  end;
+end;
+
+procedure TForm1.Button1Click(Sender: TObject);
+var
+  a1,a2:array of integer;
+  r1:array of integer;
+  i:integer;
+begin
+  SetLength(a1,4);
+  SetLength(a2,3);
+  for i := Low(a1) to High(a1) do
+    a1[i] := i;
+  for i := Low(a2) to High(a2) do
+    a2[i] := i;
+  TReturnArray(r1) := ConcatArray(a1,a2);
+  for i := Low(r1) to High(r1) do
+    showMessage(IntToStr(r1[i]));
+  Finalize(r1); //IMPORTANT!
+  ShowMessage(IntToStr(High(r1)));
+end;