Extend LOOP BEING THE ELEMENTS OF extension

[Michał "phoe" Herda]

http://www.lispworks.com/documentation/lcl50/loop/loop-50.html mentions further extensions to LOOP ... BEING THE ELEMENTS OF iteration path, for example:

;; Print the characters in a string, which is also a vector.
> (loop for x being the elements of "abcde" from 2
        do (print x))
#\c
#\d
#\e
NIL

This example currently fails on SBCL due to `FROM 2` not being expected in this LOOP context.

[Douglas Katzman (dougk)]

A loop extension would make sense only when there is no portable way to iterate on a thing.
This loop has a portable equivalent of:
(loop with v = "abcde" for i from 2 below (length v)
      for x = (aref v i) do (print x))

Quicklisp has a bunch of extensible iteration macros to choose from.

[Stas Boukarev (stassats)]

there's no portable way of iterating on sequences.