I think this is a bug in SBCL, and should be reported with its maintainers. Pascal On 10 Jun 2011, at 16:53, Tamas K Papp wrote:

Hi,

I tried to save a supplied-p parameter from a BOA constructor like this:

(defstruct (delayed-iseq (:constructor iseq (start-or-end &optional (end 0 end?) (by 1) strict-direction?))) "Delayed index sequence evaluation." start-or-end end end? by strict-direction?)

but SBCL complained that end? was not used. After rereading the CLHS page for defstruct, I am still not 100% sure why this is. My intepretation is that END? is an argument like any other, but probably I am not getting something.

Anyhow, instead I used

(defstruct delayed-iseq "Delayed index sequence evaluation." start-or-end end end? by strict-direction?)

(defun iseq (start-or-end &optional (end 0 end?) (by 1) strict-direction?) (make-delayed-iseq :start-or-end start-or-end :end end :end? end? :by by :strict-direction? strict-direction?))

Is there a way to do it in a single defstruct definition?

Best,

Tamas

PS.: (eq end nil) is different from when it is not supplied, hence the need to save end?.

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