Delphi in a Nutshell

Name

Or Keyword

Syntax

Boolean expression or Boolean expression
Integer expression or Integer expression

Description

The or operator performs a logical or if the operands are of Boolean type or a bitwise or if the operators are integers. Integer operands can be of any integer type, including Int64. A logical or is False only if both operands are False and is True if either operand is True.

Tips and Tricks

• Unlike standard Pascal, if the left-hand operand is True, Delphi does not evaluate the right-hand operand because the result must be True. You can avoid this shortcut operation and return to standard Pascal with the $BoolEval or $B compiler directives.

• An integer or operates on each bit of its operands, setting the result bit to 1 if either operand has a 1 bit, and sets a bit to if both operands have bits. If one operand is smaller than the other, Delphi extends the smaller operand with in the leftmost bits. The result is the size of the largest operand.

Examples

var
  I, J: Integer;
  S: string;
begin
  I := $25;
  J := $11;
  WriteLn(I or J); // Writes 53 (which is $35)
...
  // The short-circuit behavior of OR in the next example prevents
  // Delphi from referring to the nonexistent string element at
  // the end of the string, in case the string is empty.
  if (Length(S) = 0) or (S[Length(S)] <> '\') then
    S := S + '\';

See Also

And Keyword, Boolean Type, ByteBool Type, LongBool Type, Not Keyword, Shl Keyword, Shr Keyword, WordBool Type, Xor Keyword, $B Compiler Directive, $BoolEval Compiler Directive ...