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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;
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.
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;
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;