4gl expressions

4gl expression is a sequence of operands, operators, and parentheses treated by 4gl as a single value.

The notion of a 4gl expression is closely related to the notion of a 4gl data type. Data types characterize general categories of values. Expressions define specific data values.

4gl expressions can be used as arguments in

• other expressions
• statements
• functions
• operands
• form specifications

Data type returned by a 4gl expression depends on the syntax of this expression and the context in which it is used. Depending on the data type of the returned value, 4gl expressions can be divided into 3 major categories:

 

Numeric expressions return values of any numeric data type.

Includes

• Number expressions that return values of any of the number data types:

  with a fixed point – DECIMAL(p,s) / DEC(p,s) / NUMERIC(p,s), MONEY(p,s)

  with a floating point – DECIMAL(p) / DEC(p) / NUMERIC(p), FLOAT / DOUBLE PRECISION, SMALLFLOAT / REAL

• Integer expressions that return values of INTEGER/INT, BIGINT, SMALLINT, and TINYINT data type
• Boolean expressions that return TRUE, FALSE (or NULL in some contexts).

Character expressions return a character string of CHAR, NCHAR, VARCHAR, NVARCHAR, LVARVHAR, or STRING, data type

Time Expressions return a value that belongs to INTERVAL, DATE, or DATETIME data type

 

In this online documentation, we use the term 4GL expression to refer any of these expression types or all of them together.