R/List Logical Operator Precedence (Functions/Subroutines/Programs)

Synopsis:  The R/List logical AND operator has a higher precedence than the OR operator.  When in doubt, use parenthesis.

A problem was reported using reduce where the results were incorrect.  The syntax was something like:

… WITH <field-a> EQ <val-1> EQ <val-2> AND WITH <field-b> EQ <val-3> …

A simpler statement would process correctly:

… WITH <field-a> EQ <val-1> AND WITH <field-b> EQ <val-3> …

The reason is operator precedence.  The first is compiled as:

<field-a> = <val-1> OR <field-a> EQ <val-2> AND <field-b> EQ <val-3>

Which has a precedence of:

(<field-a> = <val-1>) OR (<field-a> EQ <val-2> AND <field-b> EQ <val-3>)

… since OR is lower than AND in precedence.  This is different from Arev (at least some versions) which would compile it as:

(<field-a> = <val-1> OR <field-a> EQ <val-2>) AND (<field-b> EQ <val-3>)

Since there was no OR in the simpler statement, it processed as expected.

Reducing using the following statement should yield the correct results:

… ( WITH <field-a> EQ <val-1> EQ <val-2> ) AND WITH <field-b> EQ <val-3> …

As an example, the first works and the second brings back "junk":

run rlist "LIST SYSREPOS JUSTLEN 50 WITH TYPEID = 'OIEVENT' AND WITH CLASSID = 'CLICK' BY @ID", 1

run rlist "LIST SYSREPOS JUSTLEN 50 WITH TYPEID = 'OIEVENT' = 'OIEVENTEXE' AND WITH CLASSID = 'CLICK' BY @ID", 1

And the corrected version of the second:

run rlist "LIST SYSREPOS JUSTLEN 50 ( WITH TYPEID = 'OIEVENT' = 'OIEVENTEXE' ) AND WITH CLASSID = 'CLICK' BY @ID", 1