Boolean expressions in forms

Some form item definitions can include boolean expressions with a form file specific syntax.

Syntax

[(] bool-expr {AND|OR} bool-expr [)] [...]

where bool-expr is:

[NOT]
{ field-tag
    {  =  expression
    |  <> expression
    |  != expression
    |  <= expression
    |  >= expression
    |  <  expression
    |  >  expression
    |  IS [NOT] NULL
    |  [NOT] BETWEEN expression AND expression
    |  [NOT] MATCHES "string"
    |  [NOT] LIKE "string"
    }
}

field-tag is the name of the current field tag in form line with the attribute definition.
expression can be the a character string, numeric or date-time literal.

Usage

Some form specification file attributes such as COLOR WHERE require a boolean expression. These boolean expressions are different from the language boolean expressions, and have a limited syntax which is specific to the form files.

When a field-tag is used in the boolean expression, the runtime system replaces field-tag at runtime with the current value in the screen field and evaluates the expression.

Example

EDIT f001 = item.price,
     COLOR=RED
          WHERE f001 >= 100 AND f001 < 1000;