These clauses cause the loop to accumulate information about the
specified Lisp form. The accumulated result is returned
from the loop unless overridden, say, by a
This clause collects the values of form into a list. Several
collect appear elsewhere in this manual.
collecting is a synonym for
likewise for the other accumulation clauses.
This clause collects lists of values into a result list using
This clause collects lists of values into a result list by destructively modifying the lists rather than copying them.
This clause concatenates the values of the specified form into a string. (It and the following clause are extensions to standard Common Lisp.)
This clause concatenates the values of the specified form into a vector.
This clause counts the number of times the specified form
evaluates to a non-
This clause accumulates the sum of the values of the specified form, which must evaluate to a number.
This clause accumulates the maximum value of the specified form,
which must evaluate to a number. The return value is undefined if
maximize is executed zero times.
This clause accumulates the minimum value of the specified form.
Accumulation clauses can be followed by ‘into var’ to
cause the data to be collected into variable var (which is
let-bound during the loop) rather than an
unnamed temporary variable. Also,
into accumulations do
not automatically imply a return value. The loop must use some
explicit mechanism, such as
finally return, to return
the accumulated result.
It is valid for several accumulation clauses of the same type to accumulate into the same place. From Steele:
(cl-loop for name in '(fred sue alice joe june) for kids in '((bob ken) () () (kris sunshine) ()) collect name append kids) ⇒ (fred bob ken sue alice joe kris sunshine june)