Is there any way to specify a slot-option for a struct slot without having to give it a default value? This can be of benefit e.g. when defining a base structure from which other structures would inherit, specifying the :types or :read-only without giving an initial value would look nicer i think.
The following structure definition leads to an error since the initial value is missing:
(defstruct s
(x :type number :read-only t)
)
No. One (of many) difference between defstruct and defclass is that all structure slots always have a value, and not specifying the default is equivalent to specifying nil default.
Note that
The restriction against issuing a warning for type mismatches between a slot-initform and the corresponding slot's
:typeoption is necessary because a slot-initform must be specified in order to specify slot options; in some cases, no suitable default may exist.
In your case, I recommend:
(defstruct s
(x (error "x is required") :type number :read-only t))
in which case (make-s) will signal an error, while (make-s :x 10) will work.
