Rainer Joswig  <joswig@lisp.de> wrote:
+---------------
| If you use DEFPARAMETER (and top-level variables) NEVER (!!!)
| use variable names like s, i, x, and so on. DEFPARAMETER
| declares a variable special and that would mean
| that local (!!!) variables with those names will be
| special, too! Convention is to use something like *s*. 
+---------------

That's why I (nearly) always use my DEFLEX macro[1] for such
top-level manually-typed variables -- it uses DEFINE-SYMBOL-MACRO
to redirect to a (related) constructed *...* name so that the
top-level variable *can* be lexically re-bound:

    > (deflex foo 11)

    FOO
    > (defparameter *bar* 22)

    *BAR*
    > (defun top-vars () (list foo *bar*))

    TOP-VARS
    > (let ((foo 33)
	    (*bar* 44))
        (list* :local foo *bar* :global (top-vars)))

    (:LOCAL 33 44 :GLOBAL 11 44)
    > 

It prevents a lot of accidents while still allowing the
convenience of names like FOO, BAR, X, Y, Z, I, J, K, S, etc.

[Though you still have to avoid names like "T"!  ;-}  ]


-Rob

[1] See <URL:news:H8Odna8j0qXvt7LbnZ2dnUVZ_viunZ2d@speakeasy.net>
    (barely a month ago) for my latest version, along with a
    pointer to a required patch to CMUCL-19c or earlier for
    symbol-macro handling in MACROEXPAND-1.

-----
Rob Warnock			<rpw3@rpw3.org>
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