Delphi語言學習6-函數參數(3)

7.數組參數

//這樣做是錯的
procedure Sort(A: array[1..10] of Integer)  // syntax error<
//這樣做是對的
type TDigits = array[1..10] of Integer;
procedure Sort(A: TDigits);
//例如
type
  TDynamicArray = array of Integer;
  procedure p(Value: TDynamicArray);
  begin
    Value[0] := 1;
  end;
  procedure Run;
var
    a: TDynamicArray;
begin
  SetLength(a, 1);
  a[0] := 0;
  p(a);
  Writeln(a[0]); // Prints '1'
end;
//Open Array Parameters
procedure Clear(var A: array of Real);
var
   I: Integer;
begin
   for I := 0 to High(A) do A[I] := 0;
end;
function Sum(const A: array of Real): Real;
var
  I: Integer;
  S: Real;
begin
  S := 0;
  for I := 0 to High(A) do S := S + A[I];
  Sum := S;
end;
//Variant Open Array Parameters
function MakeStr(const Args: array of const): string;
var
  I: Integer;
begin
  Result := '';
  for I := 0 to High(Args) do
     with Args[I] do
        case VType of
            vtInteger:  Result := Result + IntToStr(VInteger);
            vtBoolean:  Result := Result + BoolToStr(VBoolean);
            vtChar:     Result := Result + VChar;
            vtExtended: Result := Result + FloatToStr(VExtended^);
            vtString:   Result := Result + VString^;
            vtPChar:    Result := Result + VPChar;
            vtObject:   Result := Result + VObject.ClassName;
            vtClass:    Result := Result + VClass.ClassName;
            vtAnsiString:  Result := Result + string(VAnsiString);
            vtCurrency:    Result := Result + CurrToStr(VCurrency^);
            vtVariant:     Result := Result + string(VVariant^);
            vtInt64:       Result := Result + IntToStr(VInt64^);
  end;
end;
//調用方式
MakeStr(['test', 100, ' ', True, 3.14159, TForm])

8.默認參數

1）默認參數的定義和使用

procedure FillArray(A: array of Integer; Value: Integer = 0);
//使用，兩種方式都可以
FillArray(MyArray);
FillArray(MyArray, 0);

2)注意

//這樣定義是錯的
function MyFunction(X, Y: Real = 3.5): Real;  // syntax error
//這樣定義是對的
function MyFunction(X: Real = 3.5; Y: Real = 3.5): Real;