Re: force initialization of a datatype?

[Stephen Leake]

Dmitry Gutov <address@hidden> writes:

> On 11/04/2015 06:28 PM, Stephen Leake wrote:
>
>> (defun make-path-iterator (<user args>)
>>    (let ((result (vector 'cl-struct-path-iterator <slot values>)))
>>      <code to check the user args and set the slots in `result'>
>>      ))
>>
>> This code compiles and runs correctly, but I'm wondering if it is
>> acceptable style. Is there a better way to accomplish this for
>> cl-defstruct?
>
> Using `vector' looks wrong. I'm not too familiar with constructor
> syntax, but you can process each slot value before an instance gets
> constructed. See the example with &aux in
> http://www.gnu.org/software/emacs/manual/html_node/cl/Structures.html,
> or package-desc-from-define in package.el.

Thanks for the pointers.

> I'm not sure whether you can use a keyword argument with the same name
> as the slot, and convert the passed in value. That's something to try.

This works:

(cl-defstruct (path-iterator
               (:constructor nil)
               (:constructor make-path-iterator
                (user-path &aux (path (path-iter-to-truename user-path))))
               (:conc-name path-iter-)
               (:copier nil))
  path ;; user-path converted to absolute directory file truenames.

(defun path-iter-to-truename (path)
...)

However, `xref-find-definitions' doesn't find `make-path-iterator', and
there's no place to put a doc string for `make-path-iterator'.

I'll see if I can fix `xref-find-definitions'.

-- 
-- Stephe