ToC DocOverview CGDoc RelNotes Index PermutedIndex
Allegro CL

ANSI Common Lisp   6 Iteration   6.1 The LOOP Facility   6.1.8 Examples of Miscellaneous Loop Features

### 6.1.8.1 Examples of clause grouping

```;; Group conditional clauses.
(loop for i in '(1 324 2345 323 2 4 235 252)
when (oddp i)
do (print i)
and collect i into odd-numbers
and do (terpri)
else                              ; I is even.
collect i into even-numbers
finally
(return (values odd-numbers even-numbers)))
1

2345

323

235
(1 2345 323 235), (324 2 4 252)

;; Collect numbers larger than 3.
(loop for i in '(1 2 3 4 5 6)
when (and (> i 3) i)
collect it)                      ; IT refers to (and (> i 3) i).
(4 5 6)

;; Find a number in a list.
(loop for i in '(1 2 3 4 5 6)
when (and (> i 3) i)
return it)
4

;; The above example is similar to the following one.
(loop for i in '(1 2 3 4 5 6)
thereis (and (> i 3) i))
4

;; Nest conditional clauses.
(let ((list '(0 3.0 apple 4 5 9.8 orange banana)))
(loop for i in list
when (numberp i)
when (floatp i)
collect i into float-numbers
else                                  ; Not (floatp i)
collect i into other-numbers
else                                    ; Not (numberp i)
when (symbolp i)
collect i into symbol-list
else                                  ; Not (symbolp i)
do (error "found a funny value in list ~S, value ~S~%" list i)
finally (return (values float-numbers other-numbers symbol-list))))
(3.0 9.8), (0 4 5), (APPLE ORANGE BANANA)

;; Without the END preposition, the last AND would apply to the
;; inner IF rather than the outer one.
(loop for x from 0 to 3
do (print x)
if (zerop (mod x 2))
do (princ " a")
and if (zerop (floor x 2))
do (princ " b")
end
and do (princ " c"))
0  a b c
1
2  a c
3
NIL
```

© Franz Inc. 1998-2017 - File last updated 01-11-2017