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Project: Array Utilities Unit
Unit: DelphiDabbler.Lib.ArrayUtils
Record: TArrayUtils
Applies to: ~>0.1
class function EqualStart<T>(const ALeft, ARight: array of T;
const ACount: Integer; const AEqualityComparer: TEqualityComparison<T>):
Boolean;
overload; static;
class function EqualStart<T>(const ALeft, ARight: array of T;
const ACount: Integer; const AEqualityComparer: IEqualityComparer<T>):
Boolean;
overload; static;
class function EqualStart<T>(const ALeft, ARight: array of T;
const ACount: Integer): Boolean;
overload; static;
Checks if a given number of elements at the start two arrays, both with elements of the same type, have the same contents, in the same order.
Parameters:
ALeft - The first array to be compared.
ARight - The second array to be compared.
ACount - The number of bytes to be compared. Must be a positive number.
AEqualityComparer - An optional function or object that is used to test the equality of two values. Used to check equality of array elements.
If AEqualityComparer is provided it must be one of:
If the parameter is omitted then the default equality comparer defined by Delphi’s TEqualityComparer<T>.Default method is used.
Returns:
True if ALeft and ARight begin with the same ACount elements or False if not.Precondition:
1. An EAssertionFailed exception is raised otherwise.Using a comparer function:
procedure EqualStart_Eg1;
var
A, B: TArray<Integer>;
EqComparerFn: TEqualityComparison<Integer>;
begin
A := TArray<Integer>.Create(1, 2, 3);
B := TArray<Integer>.Create(1, 2, 5, 6);
EqComparerFn := function(const Left, Right: Integer): Boolean
begin
Result := Left = Right;
end;
Assert(TArrayUtils.EqualStart<Integer>(A, B, 1, EqComparerFn) = True);
Assert(TArrayUtils.EqualStart<Integer>(A, B, 2, EqComparerFn) = True);
Assert(TArrayUtils.EqualStart<Integer>(A, B, 3, EqComparerFn) = False);
end;
Using a comparer object:
procedure EqualStart_Eg2;
var
A, B: TArray<string>;
EqComparerObj: IEqualityComparer<string>;
begin
A := TArray<string>.Create('a', 'b', 'c');
B := TArray<string>.Create('a', 'b');
EqComparerObj := TDelegatedEqualityComparer<string>.Create(
SameStr,
function (const Value: string): Integer
begin
// This is only safe because the hash function isn't called by EqualStart
Result := 0;
end
);
Assert(TArrayUtils.EqualStart<string>(A, B, 2, EqComparerObj) = True);
Assert(TArrayUtils.EqualStart<string>(A, B, 3, EqComparerObj) = False);
end;