13.1.1 Assignments

Assignments give a value to a variable, replacing any previous value the variable might have had:


--                 -|-             -----  ----        ----------
  assignment statement |-vafurniacbtileonre ifdeenretnificeer-| -+:==  -| expression
                                      ---= --|
                                      - *=  -|
                                      - /=  -|

In addition to the standard Pascal assignment operator (:=), which simply replaces the value of the variable with the value resulting from the expression on the right of the := operator, Free Pascal supports some C-style constructions. All available constructs are listed in table (13.1).

Table 13.1: Allowed C constructs in Free Pascal

Assignment Result

a += b Adds b to a, and stores the result in a.
a -= b Subtracts b from a, and stores the result in a.
a *= b Multiplies a with b, and stores the result in a.
a /= b Divides a through b, and stores the result in a.

For these constructs to work, the -Sc command-line switch must be specified.

Remark: These constructions are just for typing convenience, they don’t generate different code. Here are some examples of valid assignment statements:

X := X+Y;  
X+=Y;      { Same as X := X+Y, needs -Sc command line switch}  
X/=2;      { Same as X := X/2, needs -Sc command line switch}  
Done := False;  
Weather := Good;  
MyPi := 4* Tan(1);

Keeping in mind that the dereferencing of a typed pointer results in a variable of the type the pointer points to, the following are also valid assignments:

  L : ^Longint;  
  P : PPChar;  

Note the double dereferencing in the second assignment.