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Delete<T> class method

Project: Array Utilities Unit

Unit: DelphiDabbler.Lib.ArrayUtils

Record: TArrayUtils

Applies to: ~>0.1

class procedure Delete<T>(var A: TArray<T>; const AIndex: Integer);
  overload; static;

class procedure Delete<T>(var A: TArray<T>;
  const AIndices: array of Integer);
  overload; static;

Description

Deletes the element or elements at one or more indices in an array.

Parameters:

  • A - Array from which the elements are to be deleted. The array is updated in place.

  • AIndex - Index of a single element to be deleted. (First overload only.)

    If A is empty, if AIndex < 0 or if AIndex ≥ Length(A) then no deletion takes place and A is unchanged.

  • AIndices - An integer array containing the indices of the elements to be deleted. (Second overload only.)

    If any index < 0 or ≥ Length(A) then that index is ignored.

    Duplicate indices are ignored.

    If A is empty then no deletion takes place and A is unchanged.

Examples

Example #1

This example demonstrates the overload of Delete<T> that deletes a single element an array.

procedure Delete_Eg1;
var
  A, Expected: TArray<Integer>;
begin
  A := TArray<Integer>.Create(1, 2, 3, 4, 5);

  // delete middle item
  TArrayUtils.Delete<Integer>(A, 2);
  Expected := TArray<Integer>.Create(1, 2, 4, 5);
  Assert(TArrayUtils.Equal<Integer>(Expected, A));

  // delete first item
  TArrayUtils.Delete<Integer>(A, 0);
  Expected := TArray<Integer>.Create(2, 4, 5);
  Assert(TArrayUtils.Equal<Integer>(Expected, A));

  // delete last item
  TArrayUtils.Delete<Integer>(A, 2);
  Expected := TArray<Integer>.Create(2, 4);
  Assert(TArrayUtils.Equal<Integer>(Expected, A));

  // delete invalid index < 0
  TArrayUtils.Delete<Integer>(A, -1);
  Expected := TArray<Integer>.Create(2, 4);
  Assert(TArrayUtils.Equal<Integer>(Expected, A));

  // delete invalid index = Length(A)
  TArrayUtils.Delete<Integer>(A, Length(A));
  Expected := TArray<Integer>.Create(2, 4);
  Assert(TArrayUtils.Equal<Integer>(Expected, A));
end;

Example #2

This second example shows the use of the Delete<T> overload that deletes a elements at multiple indices.

procedure Delete_Eg2;
var
  A, Expected: TArray<Integer>;
begin
  // Delete indices 0, 2, 4 and 9. We also throw in some duplicate and out of
  // range indices to show that they are ignored.
  A := TArray<Integer>.Create(0, 1, 2, 3, 4, 5, 6, 7, 8, 9);
  // the following function is identical to calling
  // TArrayUtils.Delete<Integer>(A, [0, 2, 4, 9]);
  TArrayUtils.Delete<Integer>(A, [0, 26, 2, -1, 9, 4, 9, 9, 26]);
  Expected := TArray<Integer>.Create(1, 3, 5, 6, 7, 8);
  Assert(TArrayUtils.Equal<Integer>(Expected, A));
end;

See Also