Effect Of Parentheses On Compound Logical Expressions - Tandem ENFORM 058057 Reference Manual

ENFORM Language Elements
Logical Expressions
Effect of Parentheses on
Compound Logical
Expressions
3–26
string-literal
is the pattern of characters or numbers to which the field is being compared.
String-literal must be enclosed in quotation marks.
m,n
is two integers separated by comma indicating that at least m characters but
not more than n characters must precede or follow string-literal when it is
found in a field value.
-
is a dash indicating any number of characters (0 thru 255) can precede or
follow string-literal when it is found as a field value. Specification of a dash
indicates you do not care about the contents of this part of the field.
value-range
is a range of values with the form: value-1 THRU value-2
A logical expression can be simple or compound. A simple logical expression consists
of one condition. A compound logical expression uses the boolean operators AND,
OR, and NOT to operate over two or more logical expressions.
Using the boolean operators AND, OR, and NOT has the following effect on the
evaluation of the logical expression:
When you precede a condition with the boolean operator NOT, the result of the
expression is evaluated as true if the condition is evaluated as false.
When you join two or more conditions with the boolean operator AND, the result
of the expression is evaluated as true only if all the conditions are evaluated as
true.
When you join two or more conditions with the boolean operator OR, the result of
the expression is evaluated as true if any of the conditions are evaluated as true.
Compound logical expressions are evaluated in this order:
1. Conditions within parentheses are evaluated first.
2. Conditions preceded by the boolean operator NOT are evaluated second.
3. Conditions joined with the boolean operator AND are evaluated third.
4. Conditions joined with the boolean operator OR are evaluated last.
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