Quick start manual

4-16 Delphi Language Guide
Expressions
Variable typecasts
You can cast any variable to any type, provided their sizes are the same and you do
not mix integers with reals. (To convert numeric types, rely on standard functions
like Int and Trunc.) Examples of variable typecasts include
Char(I)
Boolean(Count)
TSomeDefinedType(MyVariable)
Variable typecasts can appear on either side of an assignment statement. Thus
var MyChar: char;
ƒ
Shortint(MyChar) := 122;
assigns the character z (ASCII 122) to MyChar.
You can cast variables to a procedural type. For example, given the declarations
type Func = function(X: Integer): Integer;
var
F: Func;
P: Pointer;
N: Integer;
you can make the following assignments.
F := Func(P); { Assign procedural value in P to F }
Func(P) := F; { Assign procedural value in F to P }
@F := P; { Assign pointer value in P to F }
P := @F; { Assign pointer value in F to P }
N := F(N); { Call function via F }
N := Func(P)(N); { Call function via P }
Variable typecasts can also be followed by qualifiers, as illustrated in the following
example.
type
TByteRec = record
Lo, Hi: Byte;
end;
TWordRec = record
Low, High: Word;
end;
PByte = ^Byte;
var
B: Byte;
W: Word;
L: Longint;
P: Pointer;
begin
W := $1234;
B := TByteRec(W).Lo;
TByteRec(W).Hi := 0;
L := $01234567;
W := TWordRec(L).Low;
B := TByteRec(TWordRec(L).Low).Hi;
B := PByte(L)^;
end;