Hi Alexandrians,
Clojure has a function that I occasionally find useful, reductions. It's like
reduce, only it returns not the last value of calling the two-arg function, but
a list consisting of the first element of the input sequence, followed by the
result of calling the two-arg with the first and second elements of the input
sequence, then the result of calling the two-arg function with the previous
result and the third element, and so on... e.g.:
CL-USER> (reductions #'+ '(1 2 3 4))
(1 3 6 10)
Here's the code. There are probably better ways to do this, but this is at
least portable and simple. I think this would be a useful addition to
alexandria.
(defun reductions (function sequence &rest args)
(let ((l (list (first sequence))))
(apply #'reduce
(lambda (a b)
(let ((val (funcall function a b)))
(push val l)
val))
sequence
args)
(nreverse l)))
thanks,
Cyrus
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