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     function Pred (i: ordinal_type): ordinal_type;


     function Pred (i: ordinal_type; j: and_integer_type): ordinal_type;

or, with extended syntax (--extended-syntax or {$X+}),

     function Pred (p: Pointer_type): Pointer_type;


     function Pred (p: Pointer_type; j: and_integer_type): Pointer_type;


Returns the predecessor of the ordinal_type value i, or, if the second argument j is given, its jth predecessor. For integer values i, this is i - 1 (or i - j). (No, Pred does not work faster than plain subtraction. Both are optimized the same way, often to a single machine instruction.)

If extended syntax is on, the argument may also be a pointer value. In this case, the address is decremented by the size of the variable pointed to, or, if j is given, by j times the size of the variable pointed to. If p points to an element of an array, the returned pointer will point to the (jth) previous element of the array.

Conforming to

The Pred function is defined in ISO 7185 Pascal. The optional second parameter is defined in ISO 10206 Extended Pascal. Application of Pred to pointers is defined in Borland Pascal. The combination of the second argument with application to pointers is a GNU Pascal extension.


     program PredDemo;
       Metasyntactical = (foo, bar, baz);
       m: Metasyntactical;
       c: Char;
       a: array [1 .. 7] of Integer;
       p: ^Integer;
       m := Pred (bar);     { foo }
       c := Pred ('Z', 2);  { 'X' }
       a[1] := 42;
       a[4] := Pred (a[1]);     { 41 }
       a[5] := Pred (a[4], 3);  { 38 }
       p := @a[5];
       p := Pred (p);     { now p points to a[4] }
       p := Pred (p, 3);  { now p points to a[1] }

See also

Succ, Dec, Pointer Arithmetics.