Partitioning — Take / Skip

Partitioning operators slice a sequence without creating intermediate arrays.

Take

Take(N) returns the first N elements:

var LResult := TColligoArray<Integer>.From([1, 2, 3, 4, 5])
  .Take(3)
  .ToArray;
// Result: [1, 2, 3]

TakeWhile

TakeWhile keeps elements as long as the predicate holds, then stops:

var LResult := TColligoArray<Integer>.From([1, 2, 3, 4, 5])
  .TakeWhile(function(const X: Integer): Boolean begin Result := X < 4 end)
  .ToArray;
// Result: [1, 2, 3]

Indexed variant passes the element index:

// function TakeWhile(const APredicate: TFunc<T, Integer, Boolean>): IColligoEnumerable<T>;

TakeLast

TakeLast(N) returns the last N elements (buffers the full sequence):

var LResult := TColligoArray<Integer>.From([1, 2, 3, 4, 5])
  .TakeLast(2)
  .ToArray;
// Result: [4, 5]

Skip

Skip(N) discards the first N elements:

var LResult := TColligoArray<Integer>.From([1, 2, 3, 4, 5])
  .Skip(2)
  .ToArray;
// Result: [3, 4, 5]

SkipWhile

SkipWhile discards elements as long as the predicate holds, then returns the rest:

var LResult := TColligoArray<Integer>.From([1, 2, 3, 4, 5])
  .SkipWhile(function(const X: Integer): Boolean begin Result := X < 3 end)
  .ToArray;
// Result: [3, 4, 5]

Indexed variant:

// function SkipWhile(const APredicate: TFunc<T, Integer, Boolean>): IColligoEnumerable<T>;

SkipLast

SkipLast(N) returns all elements except the last N:

var LResult := TColligoArray<Integer>.From([1, 2, 3, 4, 5])
  .SkipLast(2)
  .ToArray;
// Result: [1, 2, 3]

ElementAt / ElementAtOrDefault

Access an element by index (zero-based):

var LValue := TColligoArray<string>.From(['a', 'b', 'c']).ElementAt(1);
// LValue = 'b'

var LSafe := TColligoArray<string>.From(['a', 'b']).ElementAtOrDefault(5);
// LSafe = '' (default string)

Pagination pattern

Combine Skip and Take for pagination:

const PageSize = 10;

procedure LoadPage(const APage: Integer; const AAll: TArray<TRecord>);
var
  LPage: IFluentArray<TRecord>;
begin
  LPage := TColligoArray<TRecord>.From(AAll)
    .Skip(APage * PageSize)
    .Take(PageSize)
    .ToArray;
end;