mdw@git.distorted.org.uk Git - lisp/blob - mdw-base.lisp

   1 ;;; -*-lisp-*-
   2 ;;;
   3 ;;; $Id$
   4 ;;;
   5 ;;; Basic definitions
   6 ;;;
   7 ;;; (c) 2005 Mark Wooding
   8 ;;;
   9
  10 ;;;----- Licensing notice ---------------------------------------------------
  11 ;;;
  12 ;;; This program is free software; you can redistribute it and/or modify
  13 ;;; it under the terms of the GNU General Public License as published by
  14 ;;; the Free Software Foundation; either version 2 of the License, or
  15 ;;; (at your option) any later version.
  16 ;;;
  17 ;;; This program is distributed in the hope that it will be useful,
  18 ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ;;; GNU General Public License for more details.
  21 ;;;
  22 ;;; You should have received a copy of the GNU General Public License
  23 ;;; along with this program; if not, write to the Free Software Foundation,
  24 ;;; Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  25
  26 ;;;--------------------------------------------------------------------------
  27 ;;; Package things.
  28
  29 (defpackage #:mdw.base
  30   (:use #:common-lisp)
  31   #+cmu (:import-from #:extensions #:fixnump))
  32
  33 (in-package #:mdw.base)
  34
  35 ;;;--------------------------------------------------------------------------
  36 ;;; Useful types.
  37
  38 (export 'unsigned-fixnum)
  39 (deftype unsigned-fixnum ()
  40   "Unsigned fixnums; useful as array indices and suchlike."
  41   `(mod ,most-positive-fixnum))
  42
  43 ;;;--------------------------------------------------------------------------
  44 ;;; Some simple macros to get things going.
  45
  46 (export 'compile-time-defun)
  47 (defmacro compile-time-defun (name args &body body)
  48   "Define a function which can be used by macros during the compilation
  49    process."
  50   `(eval-when (:compile-toplevel :load-toplevel :execute)
  51      (defun ,name ,args ,@body)))
  52
  53 (export 'show)
  54 (defmacro show (x)
  55   "Debugging tool: print the expression X and its values."
  56   (let ((tmp (gensym)))
  57     `(let ((,tmp (multiple-value-list ,x)))
  58        (fresh-line)
  59        (pprint-logical-block (*standard-output* nil :per-line-prefix ";; ")
  60          (format t
  61                  "~S = ~@_~:I~:[#<no values>~;~:*~{~S~^ ~_~}~]"
  62                  ',x
  63                  ,tmp))
  64        (terpri)
  65        (values-list ,tmp))))
  66
  67 (export 'stringify)
  68 (defun stringify (str)
  69   "Return a string representation of STR.  Strings are returned unchanged;
  70    symbols are converted to their names (unqualified!).  Other objects are
  71    converted to their print representations."
  72   (typecase str
  73     (string str)
  74     (symbol (symbol-name str))
  75     (t (princ-to-string str))))
  76
  77 (export 'functionify)
  78 (defun functionify (func)
  79   "Convert the function-designator FUNC to a function."
  80   (declare (type (or function symbol) func))
  81   (etypecase func
  82     (function func)
  83     (symbol (symbol-function func))))
  84
  85 (export 'mappend)
  86 (defun mappend (function list &rest more-lists)
  87   "Apply FUNCTION to corresponding elements of LIST and MORE-LISTS, yielding
  88    a list.  Return the concatenation of all the resulting lists.  Like
  89    mapcan, but nondestructive."
  90   (apply #'append (apply #'mapcar function list more-lists)))
  91
  92 (export 'listify)
  93 (compile-time-defun listify (x)
  94   "If X is a (possibly empty) list, return X; otherwise return (list X)."
  95   (if (listp x) x (list x)))
  96
  97 (compile-time-defun do-fix-pair (x y defaultp)
  98   "Helper function for fix-pair and pairify."
  99   (flet ((singleton (x) (values x (if defaultp y x))))
 100     (cond ((atom x) (singleton x))
 101           ((null (cdr x)) (singleton (car x)))
 102           ((atom (cdr x)) (values (car x) (cdr x)))
 103           ((cddr x) (error "Too many elements for a pair."))
 104           (t (values (car x) (cadr x))))))
 105
 106 (export 'fix-pair)
 107 (compile-time-defun fix-pair (x &optional (y nil defaultp))
 108   "Return two values extracted from X.  It works as follows:
 109      (A) -> A, Y
 110      (A B) -> A, B
 111      (A B . C) -> error
 112      (A . B) -> A, B
 113      A -> A, Y
 114    where Y defaults to A if not specified."
 115   (do-fix-pair x y defaultp))
 116
 117 (export 'pairify)
 118 (compile-time-defun pairify (x &optional (y nil defaultp))
 119   "As for fix-pair, but returns a list instead of two values."
 120   (multiple-value-call #'list (do-fix-pair x y defaultp)))
 121
 122 (export 'whitespace-char-p)
 123 (defun whitespace-char-p (ch)
 124   "Return whether CH is a whitespace character or not."
 125   (case ch
 126     (#.(loop for i below char-code-limit
 127              for ch = (code-char i)
 128              unless (with-input-from-string (in (string ch))
 129                       (peek-char t in nil))
 130              collect ch)
 131        t)
 132     (t nil)))
 133
 134 (export 'defconstant*)
 135 (defmacro defconstant* (name value &key doc test)
 136   "Define a constant, like `defconstant'.  The TEST is an equality test used
 137    to decide whether to override the current definition, if any."
 138   (let ((temp (gensym)))
 139     `(eval-when (:compile-toplevel :load-toplevel :execute)
 140        (let ((,temp ,value))
 141          (unless (and (boundp ',name)
 142                       (funcall ,(or test ''eql) (symbol-value ',name) ,temp))
 143            (defconstant ,name ,value ,@(and doc (list doc))))
 144          ',name))))
 145
 146 (export 'slot-uninitialized)
 147 (declaim (ftype (function nil ()) slot-unitialized))
 148 (defun slot-uninitialized ()
 149   "A function which signals an error.  Can be used as an initializer form in
 150    structure definitions without doom ensuing."
 151   (error "No initializer for slot."))
 152
 153 (export 'parse-body)
 154 (compile-time-defun parse-body (body &key (allow-docstring-p t))
 155   "Given a BODY (a list of forms), parses it into three sections: a
 156    docstring, a list of declarations (forms beginning with the symbol
 157    `declare') and the body forms.  The result is returned as three lists
 158    (even the docstring), suitable for interpolation into a backquoted list
 159    using `@,'.  If ALLOW-DOCSTRING-P is nil, docstrings aren't allowed at
 160    all."
 161   (let ((doc nil) (decls nil))
 162     (do ((forms body (cdr forms))) (nil)
 163       (let ((form (and forms (car forms))))
 164         (cond ((and allow-docstring-p (not doc) (stringp form) (cdr forms))
 165                (setf doc form))
 166               ((and (consp form)
 167                     (eq (car form) 'declare))
 168                (setf decls (append decls (cdr form))))
 169               (t (return (values (and doc (list doc))
 170                                  (and decls (list (cons 'declare decls)))
 171                                  forms))))))))
 172
 173 (export 'with-parsed-body)
 174 (defmacro with-parsed-body
 175     ((bodyvar declvar &optional (docvar (gensym) docp)) form &body body)
 176   "Parse FORM into a body, declarations and (maybe) a docstring; bind BODYVAR
 177    to the body, DECLVAR to the declarations, and DOCVAR to (a list
 178    containing) the docstring, and evaluate BODY."
 179   `(multiple-value-bind
 180        (,docvar ,declvar ,bodyvar)
 181        (parse-body ,form :allow-docstring-p ,docp)
 182      ,@(if docp nil `((declare (ignore ,docvar))))
 183      ,@body))
 184
 185 (export 'fixnump)
 186 #-cmu
 187 (progn
 188   (declaim (inline fixnump))
 189   (defun fixnump (object)
 190     "Answer non-nil if OBJECT is a fixnum, or nil if it isn't."
 191     (typep object 'fixnum)))
 192
 193 ;;;--------------------------------------------------------------------------
 194 ;;; Generating symbols.
 195
 196 (export 'with-gensyms)
 197 (defmacro with-gensyms (syms &body body)
 198   "Everyone's favourite macro helper."
 199   `(let (,@(mapcar (lambda (sym) `(,sym (gensym ,(symbol-name sym))))
 200                    (listify syms)))
 201      ,@body))
 202
 203 (export 'let*/gensyms)
 204 (defmacro let*/gensyms (binds &body body)
 205   "A macro helper.  BINDS is a list of binding pairs (VAR VALUE), where VALUE
 206    defaults to VAR.  The result is that BODY is evaluated in a context where
 207    each VAR is bound to a gensym, and in the final expansion, each of those
 208    gensyms will be bound to the corresponding VALUE."
 209   (labels ((more (binds)
 210              (let ((tmp (gensym "TMP")) (bind (car binds)))
 211                `((let ((,tmp ,(cadr bind))
 212                        (,(car bind) (gensym ,(symbol-name (car bind)))))
 213                    `(let ((,,(car bind) ,,tmp))
 214                       ,,@(if (cdr binds)
 215                              (more (cdr binds))
 216                              body)))))))
 217     (if (null binds)
 218         `(progn ,@body)
 219         (car (more (mapcar #'pairify (listify binds)))))))
 220
 221 ;;;--------------------------------------------------------------------------
 222 ;;; Some simple yet useful control structures.
 223
 224 (export 'nlet)
 225 (defmacro nlet (name binds &body body)
 226   "Scheme's named let."
 227   (multiple-value-bind (vars vals)
 228       (loop for bind in binds
 229             for (var val) = (pairify bind nil)
 230             collect var into vars
 231             collect val into vals
 232             finally (return (values vars vals)))
 233     `(labels ((,name ,vars
 234                 ,@body))
 235        (,name ,@vals))))
 236
 237 (export 'while)
 238 (defmacro while (cond &body body)
 239   "If COND is false, evaluate to nil; otherwise evaluate BODY and try again."
 240   `(loop (unless ,cond (return)) (progn ,@body)))
 241
 242 (export 'until)
 243 (defmacro until (cond &body body)
 244   "If COND is true, evaluate to nil; otherwise evaluate BODY and try again."
 245   `(loop (when ,cond (return)) (progn ,@body)))
 246
 247 (compile-time-defun do-case2-like (kind vform clauses)
 248   "Helper function for `case2' and `ecase2'."
 249   (with-gensyms (scrutinee argument)
 250     `(multiple-value-bind (,scrutinee ,argument) ,vform
 251        (declare (ignorable ,argument))
 252        (,kind ,scrutinee
 253          ,@(mapcar (lambda (clause)
 254                      (destructuring-bind
 255                          (cases (&optional varx vary) &rest forms)
 256                          clause
 257                        `(,cases
 258                          ,@(if varx
 259                                (list `(let ((,(or vary varx) ,argument)
 260                                             ,@(and vary
 261                                                    `((,varx ,scrutinee))))
 262                                         ,@forms))
 263                                forms))))
 264                    clauses)))))
 265
 266 (export 'caase2)
 267 (defmacro case2 (vform &body clauses)
 268   "VFORM is a form which evaluates to two values, SCRUTINEE and ARGUMENT.
 269    The CLAUSES have the form (CASES ([[SCRUVAR] ARGVAR]) FORMS...), where a
 270    standard `case' clause has the form (CASES FORMS...).  The `case2' form
 271    evaluates the VFORM, and compares the SCRUTINEE to the various CASES, in
 272    order, just like `case'.  If there is a match, then the corresponding
 273    FORMs are evaluated with ARGVAR bound to the ARGUMENT and SCRUVAR bound to
 274    the SCRUTINEE (where specified).  Note the bizarre defaulting behaviour:
 275    ARGVAR is less optional than SCRUVAR."
 276   (do-case2-like 'case vform clauses))
 277
 278 (export 'ecase2)
 279 (defmacro ecase2 (vform &body clauses)
 280   "Like `case2', but signals an error if no clause matches the SCRUTINEE."
 281   (do-case2-like 'ecase vform clauses))
 282
 283 (export 'setf-default)
 284 (defmacro setf-default (&rest specs &environment env)
 285   "Like setf, but only sets places which are currently nil.
 286
 287    The arguments are an alternating list of PLACEs and DEFAULTs.  If a PLACE
 288    is nil, the DEFAULT is evaluated and stored in the PLACE; otherwise the
 289    default is /not/ stored.  The result is the (new) value of the last
 290    PLACE."
 291   (labels ((doit (specs)
 292              (cond ((null specs) nil)
 293                    ((null (cdr specs))
 294                     (error "Odd number of arguments for SETF-DEFAULT."))
 295                    (t
 296                     (let ((place (car specs))
 297                           (default (cadr specs))
 298                           (rest (cddr specs)))
 299                       (multiple-value-bind
 300                           (vars vals store-vals writer reader)
 301                           (get-setf-expansion place env)
 302                         `(let* ,(mapcar #'list vars vals)
 303                            (or ,reader
 304                                (multiple-value-bind ,store-vals ,default
 305                                  ,writer))
 306                            ,@(and rest (list (doit rest))))))))))
 307     (doit specs)))
 308
 309 ;;;--------------------------------------------------------------------------
 310 ;;; Capturing places as symbols.
 311
 312 (defmacro %place-ref (getform setform newtmp)
 313   "Grim helper macro for with-places."
 314   (declare (ignore setform newtmp))
 315   getform)
 316
 317 (define-setf-expander %place-ref (getform setform newtmp)
 318   "Grim helper macro for with-places."
 319   (values nil nil newtmp setform getform))
 320
 321 (export 'with-places)
 322 (defmacro with-places (clauses &body body &environment env)
 323   "Define symbols which refer to `setf'-able places.
 324
 325    The syntax is similar to `let'.  The CLAUSES are a list of (NAME PLACE)
 326    pairs.  Each NAME is defined as a symbol-macro referring to the
 327    corresponding PLACE: a mention of the NAME within the BODY forms extracts
 328    the current value(s) of the PLACE, while a `setf' (or `setq', because
 329    symbol macros are strange like that) of a NAME updates the value(s) in the
 330    PLACE.  The returned values are those of the BODY, evaluated as an
 331    implicit `progn'."
 332
 333   (let ((temp-binds nil)
 334         (macro-binds nil))
 335     (dolist (clause clauses)
 336       (destructuring-bind (name place) clause
 337         (multiple-value-bind (valtmps valforms newtmps setform getform)
 338             (get-setf-expansion place env)
 339           (setf temp-binds
 340                 (nconc (nreverse (mapcar #'list valtmps valforms))
 341                        temp-binds))
 342           (push `(,name (%place-ref ,getform ,setform ,newtmps))
 343                 macro-binds))))
 344     `(let (,@(nreverse temp-binds))
 345        (symbol-macrolet (,@(nreverse macro-binds))
 346          ,@body))))
 347
 348 (export 'with-places/gensyms)
 349 (defmacro with-places/gensyms (clauses &body body)
 350   "A kind of a cross between `with-places' and `let*/gensyms'.
 351
 352    This is a hairy helper for writing `setf'-like macros.  The CLAUSES are a
 353    list of (NAME [PLACE]) pairs, where the PLACE defaults to NAME, and a
 354    bare NAME may be written in place of the singleton list (NAME).  The
 355    PLACEs are evaluated.
 356
 357    The BODY forms are evaluated as an implicit `progn', with each NAME bound
 358    to a gensym, to produce a Lisp form, called the `kernel'.  The result of
 359    the `with-places/gensyms' macro is then itself a Lisp form, called the
 360    `result'.
 361
 362    The effect of evaluating the `result' form is to evaluate the `kernel'
 363    form with each of the gensyms stands for the value(s) stored in the
 364    corresponding PLACE; a `setf' (or `setq') of one of the gensyms updates
 365    the value(s) in the corresponding PLACE.  The values returned by the
 366    `result' form are the values returned by the `kernel'."
 367
 368   (let* ((clauses (mapcar #'pairify clauses))
 369          (names (mapcar #'car clauses))
 370          (places (mapcar #'cadr clauses))
 371          (gensyms (mapcar (lambda (name) (gensym (symbol-name name)))
 372                           names)))
 373     ``(with-places (,,@(mapcar (lambda (gensym place)
 374                                  ``(,',gensym ,,place))
 375                                gensyms places))
 376         ,(let (,@(mapcar (lambda (name gensym)
 377                            `(,name ',gensym))
 378                          names gensyms))
 379            ,@body))))
 380
 381 ;;;--------------------------------------------------------------------------
 382 ;;; Update-in-place macros built using with-places.
 383
 384 (export 'update-place)
 385 (defmacro update-place (op place &rest args)
 386   "Update PLACE with (OP PLACE . ARGS), returning the new value."
 387   (with-places/gensyms (place)
 388     `(setf ,place (,op ,place ,@args))))
 389
 390 (export 'update-place-after)
 391 (defmacro update-place-after (op place &rest args)
 392   "Update PLACE with (OP PLACE . ARGS), returning the old value."
 393   (with-places/gensyms (place)
 394     (with-gensyms (x)
 395       `(let ((,x ,place))
 396          (setf ,place (,op ,x ,@args))
 397          ,x))))
 398
 399 (export 'incf-after)
 400 (defmacro incf-after (place &optional (by 1))
 401   "Increment PLACE by BY, returning the old value."
 402   `(update-place-after + ,place ,by))
 403
 404 (export 'decf-after)
 405 (defmacro decf-after (place &optional (by 1))
 406   "Decrement PLACE by BY, returning the old value."
 407   `(update-place-after - ,place ,by))
 408
 409 ;;;--------------------------------------------------------------------------
 410 ;;; Locatives.
 411
 412 (export 'locp)
 413 (defstruct (loc (:predicate locp) (:constructor make-loc (reader writer)))
 414   "Locative data type.  See `locf' and `ref'."
 415   (reader (slot-uninitialized) :type function)
 416   (writer (slot-uninitialized) :type function))
 417
 418 (export 'locf)
 419 (defmacro locf (place &environment env)
 420   "Slightly cheesy locatives.  (locf PLACE) returns an object which, using
 421    the `ref' function, can be used to read or set the value of PLACE.  It's
 422    cheesy because it uses closures rather than actually taking the address of
 423    something.  Also, unlike Zetalisp, we don't overload `car' to do our dirty
 424    work."
 425   (multiple-value-bind
 426       (valtmps valforms newtmps setform getform)
 427       (get-setf-expansion place env)
 428     `(let* (,@(mapcar #'list valtmps valforms))
 429        (make-loc (lambda () ,getform)
 430                  (lambda (,@newtmps) ,setform)))))
 431
 432 (export 'ref)
 433 (declaim (inline ref (setf ref)))
 434 (defun ref (loc)
 435   "Fetch the value referred to by a locative."
 436   (funcall (loc-reader loc)))
 437 (defun (setf ref) (new loc)
 438   "Store a new value in the place referred to by a locative."
 439   (funcall (loc-writer loc) new))
 440
 441 (export 'with-locatives)
 442 (defmacro with-locatives (locs &body body)
 443   "LOCS is a list of items of the form (SYM [LOC-EXPR]), where SYM is a
 444    symbol and LOC-EXPR evaluates to a locative.  If LOC-EXPR is omitted, it
 445    defaults to SYM.  As an abbreviation for a common case, LOCS may be a
 446    symbol instead of a list.  The BODY is evaluated in an environment where
 447    each SYM is a symbol macro which expands to (ref LOC-EXPR) -- or, in fact,
 448    something similar which doesn't break if LOC-EXPR has side-effects.  Thus,
 449    references, including `setf' forms, fetch or modify the thing referred to
 450    by the LOC-EXPR.  Useful for covering over where something uses a
 451    locative."
 452   (setf locs (mapcar #'pairify (listify locs)))
 453   (let ((tt (mapcar (lambda (l) (declare (ignore l)) (gensym)) locs))
 454         (ll (mapcar #'cadr locs))
 455         (ss (mapcar #'car locs)))
 456     `(let (,@(mapcar (lambda (tmp loc) `(,tmp ,loc)) tt ll))
 457        (symbol-macrolet (,@(mapcar (lambda (sym tmp)
 458                                      `(,sym (ref ,tmp))) ss tt))
 459          ,@body))))
 460
 461 ;;;----- That's all, folks --------------------------------------------------