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OccurrencesOf<T> class method

Project: Array Utilities Unit

Unit: DelphiDabbler.Lib.ArrayUtils

Record: TArrayUtils

Applies to: ~>0.1

class function OccurrencesOf<T>(const AItem: T; const A: array of T;
  const AEqualityComparer: TEqualityComparison<T>): Integer;
  overload; static;

class function OccurrencesOf<T>(const AItem: T; const A: array of T;
  const AEqualityComparer: IEqualityComparer<T>): Integer;
  overload; static;

class function OccurrencesOf<T>(const AItem: T;
  const A: array of T): Integer;
  overload; static;

Description

Returns the number of elements of an array that are equal to a given value.

Parameters:

Returns:

Examples

Example #1

Using an equality comparer function:

procedure OccurrencesOf_Eg1;
var
  A: TArray<Integer>;
  EqComparerFn: TEqualityComparison<Integer>;
begin
  A := TArray<Integer>.Create(1, 2, 3, 4, 2, 3, 2);
  EqComparerFn := function(const Left, Right: Integer): Boolean
    begin
      Result := Left = Right;
    end;
  Assert(TArrayUtils.OccurrencesOf<Integer>(2, A, EqComparerFn) = 3);
  Assert(TArrayUtils.OccurrencesOf<Integer>(5, A, EqComparerFn) = 0);
end;

Example #2

Using an equality comparer object:

procedure OccurrencesOf_Eg2;
var
  A: TArray<string>;
  EqComparerObj: IEqualityComparer<string>;
begin
  A := TArray<string>.Create('A', 'B', 'C', 'd', 'c', 'a');
  EqComparerObj := TDelegatedEqualityComparer<string>.Create(
    SameText,
    function(const Value: string): Integer
    begin
      // only do this if you KNOW the hash function won't be called
      Result := 0;
    end
  );
  Assert(TArrayUtils.OccurrencesOf<string>('C', A, EqComparerObj) = 2);
  Assert(TArrayUtils.OccurrencesOf<string>('x', A, EqComparerObj) = 0);
end;

See Also