;;;; hyperquirks.lisp

(in-package #:hyperquirks)

;;; MACROS

(defmacro defvarf (var &optional val doc)
  `(progn
     (defvar ,var nil ,doc)
     (setf ,var ,val)))

(defmacro imperative (&body body)
   "Evaluate expressins in BODY in sequence. Expressions that look
 like (:= VAR1 EXPR1 ...) will expand into a LET* form whose bindings
 are valid for the rest of the BODY

 E.g.

 (imperative 
   (format t \"Welcome to IMPERATIVE\") 
   (terpri)
   (:= x 10 z (+ x 20))
   (format t \"X = ~a, Z = ~a~%\" x z)
   (:= y (+ z 20))
   (format t \"Y = ~a~%\" y)
   (list x y z))

 would evaluate to:

 Welcome to IMPERATIVE    ;; <-- printed to stdout
 X = 10, Z = 30
 Y = 50
 
(10 50 30)     ;; <-- return value

IMPERATIVE introduces an implicit, anonymous BLOCK, and hence can be
returned from.
 "
   (labels ((binding-form-p (form)
              (and (consp form)
                   (keywordp (first form))
                   (eql := (first form))))
            (collect-bindings (bindings)
              (loop for (var expr . more) on bindings by #'cddr
                    collect (list var expr)))
            (expander (body)
              (cond
                ((null body) body)
                ((binding-form-p (first body))
                 (list (list* 'let* (collect-bindings (rest (first body)))
                              (expander (rest body)))))
                (t
                 (cons (first body)
                       (expander (rest body)))))))
     `(block () ,@(expander body))))

(defmacro >> ((ob) &rest accessors)
  "Chain access to OB. "
  (let* ((tmpvar
           (gensym))
         (block-name
           (gensym))
         (body
           (loop for a in accessors
                 when (symbolp a)
                   collect `(setf ,tmpvar (funcall ',a ,tmpvar))
                 else
                   collect `(setf ,tmpvar (funcall ,a ,tmpvar)))))
    `(block ,block-name
         (let ((,tmpvar ,ob))
           ,@body))))


(defmacro ?> ((ob &optional default (test 'null)) &rest accessors)
  "Chain access to OB, returning DEFAULT the first time TEST returns null.
E.g. 


> (let ((num-tree '(1 (2 3 (4 5) 6))))
    (?> (num-tree) second third fourth))
NIL

> (let ((num-tree '(1 (2 3 (4 5) 6))))
    (?> (num-tree) second third first))
4
"
  (let* ((tmpvar
           (gensym "TEMP"))
         (block-name
           (gensym "BLOCK"))
         (body
           (loop for a in accessors
                 collect `(when (funcall ',test ,tmpvar)
                            (return-from ,block-name ,default))
                 when (symbolp a)
                   collect `(setf ,tmpvar (funcall ',a ,tmpvar))
                 else
                   collect `(setf ,tmpvar (funcall ,a ,tmpvar)))))
    `(block ,block-name
         (let ((,tmpvar ,ob))
           ,@body))))


(defmacro imperative-cond (&body clauses)
  "Like cond except the first form of every clause is a binding form
alá IMPERATIVE. 

E.g. 

(imperative-cond 
   ((:= x (and (zerop (random 2)) 10)
        y 11)
    (list :x x :y y))
   (t
     12))


That would bind x and y in the first clause, check both both are non
nil, and if they are, return the evaluated body, in this case (list :x x :y y)

Otherwise 12 would be returned."

  (let ((imperative-body 
          (loop for (bindings . body) in clauses
                for vars = (unless (eq t bindings)
                             (loop for (var _ . more) on (rest bindings) by #'cddr
                                   collect var))
                collect bindings
                collect `(when (and ,@vars) (return (progn ,@body))))))
    `(imperative ,@imperative-body)))



(defmacro with-plist (vars plist &body body)
  "Extract some properties from a property list, bind them to a variable
with the same name as the property, and execute the body.

PLIST is any expression that evaluates to a propety list. 

E.g. 

(let ((me (list :name \"colin\" 'age 40 :occupation :slacker)))
   (with-plist (name age occupation) me
      (format t \"My name is ~a, and I am a ~a year old ~a~%\" 
        name age occupation)))

Will print out:
My name is colin, and I am a 40 year old SLACKER

Notice that the keys in the PLIST can be eitehr keywords or symbols in
some other package.
"
  (let* ((plist-var
           (gensym))
         (bindings
           (loop for var in vars
                 for keyword-var = (intern (symbol-name var) 'keyword)
                 collect `(,var (or (getf ,plist-var ,keyword-var)
                                    (getf ,plist-var ',var))))))
    `(let ((,plist-var ,plist))
       (let ,bindings
         ,@body))))


(defmacro with-leaves (leaf-var tree &body body)
  "Binds each atom in TREE to LEAF-VAR and then executes BODY."
  (let ((tree-var (gensym))
        (ignore-var (gensym)))
    `(let ((,tree-var ,tree))
       (tree-equal ,tree-var ,tree-var
                   :test (lambda (,leaf-var ,ignore-var)
                           (declare (ignore ,ignore-var))
                           ,@body
                           t)))))



;;; LIST FUNCTIONS

(defun group (n xs &optional default)
  "Group a list XS into consequtive sublists of size N, using the
DEFAULT to fill in any remainder in the case the length of XS is not
neatly divisible by N."
  (loop for l on xs by (lambda (l) (nthcdr n l))
        when (<= n (length l))
          collect (subseq l 0 n)
        else
          collect (append l (loop repeat (- n (length l)) collect default))))


;;; STRING FUNCTIONS

(defun tabulate
    (objects line-width col-count
     &key
       (default-fill #\space)
       (stream t)
       (object-formatter "~a"))
"Print a table of OBJECTS to STREAM. The table will be LINE-WIDTH
chracters wide and each line will have COL-COUNT columns. 

The objects are formatted with the format string OBJECT-FORMATTER,
which defaults to ~a. DEFAULT-FILL is used to fill in blanks in the
table."
  (let ((row-format
          (apply 'concatenate 'string
                 "~" (prin1-to-string line-width) "<"
                 (loop for i from 1 to col-count
                       collect object-formatter
                       when (< i col-count)
                         collect "~;"
                       else
                         collect "~>~%"))))
    (dolist (g (group col-count objects default-fill))
      (apply #'format stream row-format g))))