Assignment Operator

The rules language uses the equal sign (=) as the assignment operator.

The following chart shows which fields and values with the following semantic data types can be assigned to each other. In each case, the semantic data type of the result is the semantic data type of the left operand, unless the left operand is a local variable. If the left operand is a local variable, the semantic data type of the result is the semantic type of the right operand. Y indicates a valid operation.


	COUNT	DATE	IDENTIFIER	LOGICAL	QUANTITY	STRING	Typeless
COUNT	Y		Y			Y	Y
DATE		Y				Y	Y
IDENTIFIER	Y		Y			Y	Y
LOGICAL				Y			Y
QUANTITY					Y	Y	Y
STRING	Y	Y	Y		Y	Y	Y
Typeless	Y	Y	Y	Y	Y	Y	Y


	An assignment of a string field to a date field can cause unexpected results if the default date format of your installation contains a two-digit year, for example, YYDDD or YYWW.

Types of Assignment Statements

Use assignment statements to assign values to fields or to local variables. There are two kinds of assignment statements:

•

Simple assignment

•

Assignment-by-name

Syntax of Assignment Statements

Simple Assignment of a Value

In simple assignment, a single value is assigned to a field of a table or to a local variable.

Syntax

<assignment target> ::=

Examples

Two examples of simple assignment statements are:

CARS.PRICE = (PRICES.BASE + PRICES.SHIPPING)* TAXES.RETAIL;

AMOUNT = PRINCIPAL * (1 + INTEREST) ** YEARS;

Assigning Values by Name

In assignment-by-name, the field values of the table on the right are assigned to identically named fields of the table on the left. The field names are replaced with the asterisk symbol (*) for both the source and target tables.

Syntax

<table reference>.* =<table reference>.*

<table reference>.* = NULL

Example

INPUTORDERS.* = ORDERS.* ;

Assignment Relationship

One use of assignment-by-name assigns the values of fields of a screen table to fields of a data table, or vice versa. The following illustrates the assignment relationship between the screen fields in the screen table INPUTORDERS and the fields in the ORDERS table, as viewed in a user’s application:

Initializing All the Fields of a Table

Assignment-by-name is a convenient way to initialize all the fields of a table. For example:

ORDERS.* = NULL;

This statement initializes all the fields in the ORDERS table to null values.