expression

An expression is a non-productive rule that resolves by calculation into a value. They consist of at least one operand, and additional operands may be linked via non-unary operators. An operand may be

• a literal value of any type,
• a variable or constant referred to by its identifier, or
• a function call.

Examples of expressions are:

• x + 5
• 'Z'
• response <> 42

Expressions, and parts thereof, can be classified by their result type. Usually primarily arithmetic and logic expressions are distinguished. An arithmetic expression results in a numeric value. A logic expression results in a Boolean value.

remarks

With compiler directive {$extendedSyntax on} a function call as an expression can appear as a statement, too. This is useful if the function triggers side-effects, but the return value is not needed.

see also

• article „expression“ in Wikipedia, the free online encyclopedia
• Tutorial: Boolean expressions
• Tutorial: How to use tFPExpressionParser (if an expression entered by the user shall be interpreted)

---

From the Free Pascal wiki, page "expression", as it stood on 2023-01-25 after a change by Kai Burghardt, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's Licensing page. If you have concerns about this material, message the admin.