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* derrida
`DERRIDA` is a library for destructuring common "object-like" structures in Common Lisp.
More specifically, it provides forms that act like `WITH-SLOTS` for "object-like" or "map-like" data structure.
It provides forms for digging into association lists, property lists,
and struct instances and CLOS class instances.
** Examples
*** Property Lists
#+begin_src lisp
(let ((pl
(list 'name \"colin\" :age 40 :|currentJob| :crumb-bum)))
(with-plist (name (age :age) (job :|currentJob|)) pl
(setf age (1+ age))
(format t \"~a the ~a had a birthday, and is now ~a years old~%\"
name job age)
pl))
#+end_src
The above would print out:
: colin the CRUMB-BUM had a birthday, and is now 41 years old
And would return
: (NAME \"colin\" :AGE 41 :|currentJob| :CRUMB-BUM)"
*** Nested Property Lists
#+begin_src lisp
> (defvar *pl* '(:x (:a 10) :y (:b 20))
*PL*
> (with-keypaths ((a :x :a)
(b :y :b)
(d :y :d)) *pl*
(incf a)
(setf d (* a b)))
220
> *pl*
(:X (:A 11) :Y (:D 220 :B 20))"
#+end_src
*** Nested Instances
#+begin_src lisp
> (defclass point () ((x :initform 0) (y :initform 0)))
#<STANDARD-CLASS DERRIDA::POINT>
> (defclass in-space ()
((location :initform (make-instance 'point))))
#<STANDARD-CLASS DERRIDA::IN-SPACE>
> (defvar *thing* (make-instance 'in-space))
*THING*
> (with-slot-paths
((x 'location 'x)
(y 'location 'y)) *thing*
(setf x 10
y -30))
-30
> (describe (slot-value *thing* 'location))
#<POINT {100781DB53}>
[standard-object]
Slots with :INSTANCE allocation:
X = 10
Y = -30"
#+end_src
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