System.Dec Function

Decrements a variable by 1 or N.

Pascal

procedure Dec(var X); overload;
procedure Dec(var X; N: Longint); overload;

C++

Dec( X);
Dec( X, Longint N);

File

System

Description

In Delphi code, Dec subtracts one or N from a variable.

X is a variable of an ordinal type (including Int64), or a pointer type if the extended syntax is enabled.

N is an integer-type expression.

X decrements by 1, or by N if N is specified; that is, Dec(X) corresponds to the statement X := X - 1, and Dec(X, N) corresponds to the statement X := X - N. On some platforms, Dec may generate optimized code, especially useful in tight loops.

If X is a pointer type, it decrements X by N times the size of the type pointed to. Thus, given

Copy Code

type
  PMyType = ^TMyType;

and

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var
  P: PMyType;

the statement Dec(P) decrements P by SizeOf(TMyType).

Warning: Do not use Dec on ordinal-type properties if the property uses a write procedure.