form—a form.
results—the values resulting from the evaluation of
the last form, or the symbols nil or t.
The macro and evaluates each form one at a time from left to right.
As soon as any form evaluates to nil, and returns
nil without evaluating the remaining forms. If all forms
but the last evaluate to true values, and returns the results
produced by evaluating the last form.
If no forms are supplied, (and) returns t.
and passes back multiple values from the last subform
but not from subforms other than the last.
(if (and (>= n 0)
(< n (length a-simple-vector))
(eq (elt a-simple-vector n) 'foo))
(princ "Foo!"))
The above expression prints Foo! if element n of a-simple-vector
is the symbol foo, provided also that n is indeed a valid index
for a-simple-vector. Because and guarantees
left-to-right testing
of its parts, elt is not called if n is out of range.
(setq temp1 1 temp2 1 temp3 1) → 1 (and (incf temp1) (incf temp2) (incf temp3)) → 2 (and (eql 2 temp1) (eql 2 temp2) (eql 2 temp3)) → true (decf temp3) → 1 (and (decf temp1) (decf temp2) (eq temp3 'nil) (decf temp3)) → NIL (and (eql temp1 temp2) (eql temp2 temp3)) → true (and) → T
cond, every, if, or (Macro), when
(and form) ≡ (let () form) (and form1 form2 ...) ≡ (when form1 (and form2 ...))