How to create a list of consecutive numbers in Common Lisp?
In other words, what is the equivalent of Python's
range function in Common Lisp?
range(2, 10, 2) returns
[2, 4, 6, 8], with first and last arguments being optional. I couldn't find the idiomatic way to create a sequence of numbers, though Emacs Lisp has
Range could be emulated using loop macro, but i want to know the accepted way to generate a sequence of numbers with start and end points and step.
Related: Analog of Python's range in Scheme
There is no built-in way of generating a sequence of numbers, the canonical way of doing so is to do one of:
An example implementation would be (this only accepts counting "from low" to "high"):
(defun range (max &key (min 0) (step 1)) (loop for n from min below max by step collect n))
This allows you to specify an (optional) minimum value and an (optional) step value.
To generate odd numbers:
(range 10 :min 1 :step 2)
alexandria implements scheme's iota:
(ql:quickload :alexandria) (alexandria:iota 4 :start 2 :step 2) ;; (2 4 6 8)