Delphi in a Nutshell

Chapter 7. Operators

This chapter describes the symbolic operators, their precedence and semantics. Chapter 5, describes the named operators in depth, but not the symbolic operators, because it’s hard to alphabetize symbols. This chapter describes the symbolic operators in depth.

Delphi defines the following operators. Each line lists the operators with the same precedence; operator precedence is highest at the start of the list and lowest at the bottom:

@ not ^ + - (unary operators)

* / div mod and shl shr as

+ - or xor

> < >= <= <> = in is

A Variant can be a string, number, Boolean, or other value. If an expression mixes Variant and non-Variant operands, Delphi converts all operands to Variant. If the Variant types do not match, Delphi casts one or both operands as needed for the operation, and produces a Variant result. See the Variant type in Chapter 5 for more information about Variant type casts.

Unary Operators

@ operator

Returns the address of its operand. The address of a variable or ordinary subroutine is a Pointer, or if the $T or $TypedAddress compiler directive is used, a typed pointer (e.g., PInteger).

The address of a method has two parts: a code pointer and a data pointer, so you can assign a method address only to a variable of the appropriate type, and not to a generic Pointer variable. If you take the address of a method using a class reference instead of an object reference, the @ operator returns just the code pointer. For example:

Ptr := @TObject.Free;