declares a procedure called
TakeAnything
that accepts a parameter of any type. When you call such a routine,
you cannot pass it a numeral or untyped numeric constant.
Within a procedure or function body, untyped parameters are incompatible with every type. To operate on an untyped
parameter, you must cast it. In general, the compiler cannot verify that operations on untyped parameters are valid.
The following example uses untyped parameters in a function called
Equal
that compares a specified number of
bytes of any two variables.
function Equal(var Source, Dest; Size: Integer): Boolean;
type
TBytes = array[0..MaxInt - 1] of Byte;
var
N : Integer;
begin
N := 0;
while (N < Size) and (TBytes(Dest)[N] = TBytes(Source)[N]) do
Inc(N);
Equal := N = Size;
end;
Given the declarations
type
TVector = array[1..10] of Integer;
TPoint = record
X, Y: Integer;
end;
var
Vec1, Vec2: TVector;
N: Integer;
P: TPoint;
you could make the following calls to
Equal
:
Equal(Vec1, Vec2, SizeOf(TVector)); // compare Vec1 to Vec2
Equal(Vec1, Vec2, SizeOf(Integer) * N); // compare first N elements of Vec1 and Vec2
Equal(Vec1[1], Vec1[6], SizeOf(Integer) * 5); // compare first 5 to last 5 elements of Vec1
Equal(Vec1[1], P, 4); // compare Vec1[1] to P.X and Vec1[2] to P.Y
Dostları ilə paylaş: 
