Goals may be combined using the forms `%and`

and `%or`

to form compound goals. (For `%not`

, see sec 8.2.)
Eg,

(%which (x) (%and (%member x '(1 2 3)) (%< x 3)))

gives solutions for `x`

that satisfy both the
argument goals of the `%and`

.
Ie, `x`

should both be a member of `'(1 2 3)`

*and* be less than `3`

. The first
solution is

([x 1])

Typing `(%more)`

gives another solution:

([x 2])

There are no more solutions, because `[x 3]`

satisfies
the first but not the second goal.

Similarly, the query

(%which (x) (%or (%member x '(1 2 3)) (%member x '(3 4 5))))

lists all `x`

that are members of either list.

([x 1]) (%more) =>([x 2]) (%more) =>([x 3]) (%more) =>([x 3]) (%more) =>([x 4]) (%more) =>([x 5])

(Yes, `([x 3])`

is listed twice.)

We can rewrite the predicate `%computer‑literate`

from sec 2.2 using `%and`

and `%or`

:

(define %computer-literate (%rel (person) [(person) (%or (%and (%knows person 'TeX) (%knows person 'Scheme)) (%and (%knows person 'TeX) (%knows person 'Prolog)))]))

Or, more succinctly:

(define %computer-literate (%rel (person) [(person) (%and (%knows person 'TeX) (%or (%knows person 'Scheme) (%knows person 'Prolog)))]))

We can even dispense with the `%rel`

altogether:

(define %computer-literate (lambda (person) (%and (%knows person 'TeX) (%or (%knows person 'Scheme) (%knows person 'Prolog)))))

This last looks like a conventional Scheme predicate definition, and is arguably the most readable format for a Scheme programmer.