src/code/eval.lisp

   1 ;;;; EVAL and friends
   2
   3 ;;;; This software is part of the SBCL system. See the README file for
   4 ;;;; more information.
   5 ;;;;
   6 ;;;; This software is derived from the CMU CL system, which was
   7 ;;;; written at Carnegie Mellon University and released into the
   8 ;;;; public domain. The software is in the public domain and is
   9 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
  10 ;;;; files for more information.
  11
  12 (in-package "SB!IMPL")
  13
  14 ;;; general case of EVAL (except in that it can't handle toplevel
  15 ;;; EVAL-WHEN magic properly): Delegate to #'COMPILE.
  16 (defun %simple-eval (expr lexenv)
  17   ;; FIXME: It might be nice to quieten the toplevel by muffling
  18   ;; warnings generated by this compilation (since we're about to
  19   ;; execute the results irrespective of the warnings).  We might want
  20   ;; to be careful about not muffling warnings arising from inner
  21   ;; evaluations/compilations, though [e.g. the ignored variable in
  22   ;; (DEFUN FOO (X) 1)].  -- CSR, 2003-05-13
  23   (let* (;; why PROGN?  So that attempts to eval free declarations
  24          ;; signal errors rather than return NIL.  -- CSR, 2007-05-01
  25          (lambda `(lambda () (progn ,expr)))
  26          (fun (sb!c:compile-in-lexenv nil lambda lexenv)))
  27     (funcall fun)))
  28
  29 ;;; Handle PROGN and implicit PROGN.
  30 (defun simple-eval-progn-body (progn-body lexenv)
  31   (unless (list-with-length-p progn-body)
  32     (let ((*print-circle* t))
  33       (error 'simple-program-error
  34              :format-control
  35              "~@<not a proper list in PROGN or implicit PROGN: ~2I~_~S~:>"
  36              :format-arguments (list progn-body))))
  37   ;; Note:
  38   ;;   * We can't just use (MAP NIL #'EVAL PROGN-BODY) here, because we
  39   ;;     need to take care to return all the values of the final EVAL.
  40   ;;   * It's left as an exercise to the reader to verify that this
  41   ;;     gives the right result when PROGN-BODY is NIL, because
  42   ;;     (FIRST NIL) = (REST NIL) = NIL.
  43   (do* ((i progn-body rest-i)
  44         (rest-i (rest i) (rest i)))
  45       (nil)
  46     (if rest-i ; if not last element of list
  47         (simple-eval-in-lexenv (first i) lexenv)
  48         (return (simple-eval-in-lexenv (first i) lexenv)))))
  49
  50 (defun simple-eval-locally (exp lexenv &key vars)
  51   (multiple-value-bind (body decls)
  52       (parse-body (rest exp) :doc-string-allowed nil)
  53     (let ((lexenv
  54            ;; KLUDGE: Uh, yeah.  I'm not anticipating
  55            ;; winning any prizes for this code, which was
  56            ;; written on a "let's get it to work" basis.
  57            ;; These seem to be the variables that need
  58            ;; bindings for PROCESS-DECLS to work
  59            ;; (*FREE-FUNS* and *FREE-VARS* so that
  60            ;; references to free functions and variables
  61            ;; in the declarations can be noted;
  62            ;; *UNDEFINED-WARNINGS* so that warnings about
  63            ;; undefined things can be accumulated [and
  64            ;; then thrown away, as it happens]). -- CSR,
  65            ;; 2002-10-24
  66            (let* ((sb!c:*lexenv* lexenv)
  67                   (sb!c::*free-funs* (make-hash-table :test 'equal))
  68                   (sb!c::*free-vars* (make-hash-table :test 'eq))
  69                   (sb!c::*undefined-warnings* nil))
  70              ;; FIXME: VALUES declaration
  71              (sb!c::process-decls decls
  72                                   vars
  73                                   nil
  74                                   :lexenv lexenv
  75                                   :context :eval))))
  76       (simple-eval-progn-body body lexenv))))
  77
  78 ;;;; EVAL-ERROR
  79 ;;;;
  80 ;;;; Analogous to COMPILER-ERROR, but simpler.
  81
  82 (define-condition eval-error (encapsulated-condition)
  83   ()
  84   (:report (lambda (condition stream)
  85              (print-object (encapsulated-condition condition) stream))))
  86
  87 (defun eval-error (condition)
  88   (signal 'eval-error :condition condition)
  89   (bug "Unhandled EVAL-ERROR"))
  90
  91 ;;; Pick off a few easy cases, and the various top level EVAL-WHEN
  92 ;;; magical cases, and call %SIMPLE-EVAL for the rest.
  93 (defun simple-eval-in-lexenv (original-exp lexenv)
  94   (declare (optimize (safety 1)))
  95   ;; (aver (lexenv-simple-p lexenv))
  96   (handler-bind
  97       ((sb!c:compiler-error
  98         (lambda (c)
  99           (if (boundp 'sb!c::*compiler-error-bailout*)
 100               ;; if we're in the compiler, delegate either to a higher
 101               ;; authority or, if that's us, back down to the
 102               ;; outermost compiler handler...
 103               (progn
 104                 (signal c)
 105                 nil)
 106               ;; ... if we're not in the compiler, better signal the
 107               ;; error straight away.
 108               (invoke-restart 'sb!c::signal-error)))))
 109     (let ((exp (macroexpand original-exp lexenv)))
 110       (handler-bind ((eval-error
 111                       (lambda (condition)
 112                         (error 'interpreted-program-error
 113                                :condition (encapsulated-condition condition)
 114                                :form exp))))
 115         (typecase exp
 116           (symbol
 117            (ecase (info :variable :kind exp)
 118              (:constant
 119               (values (info :variable :constant-value exp)))
 120              ((:special :global)
 121               (symbol-value exp))
 122              ;; FIXME: This special case here is a symptom of non-ANSI
 123              ;; weirdness in SBCL's ALIEN implementation, which could
 124              ;; cause problems for e.g. code walkers. It'd probably be
 125              ;; good to ANSIfy it by making alien variable accessors
 126              ;; into ordinary forms, e.g. (SB-UNIX:ENV) and (SETF
 127              ;; SB-UNIX:ENV), instead of magical symbols, e.g. plain
 128              ;; SB-UNIX:ENV. Then if the old magical-symbol syntax is to
 129              ;; be retained for compatibility, it can be implemented
 130              ;; with DEFINE-SYMBOL-MACRO, keeping the code walkers
 131              ;; happy.
 132              (:alien
 133               (%simple-eval original-exp lexenv))))
 134           (list
 135            (let ((name (first exp))
 136                  (n-args (1- (length exp))))
 137              (case name
 138                ((function)
 139                 (unless (= n-args 1)
 140                   (error "wrong number of args to FUNCTION:~% ~S" exp))
 141                 (let ((name (second exp)))
 142                   (if (and (legal-fun-name-p name)
 143                            (not (consp (let ((sb!c:*lexenv* lexenv))
 144                                          (sb!c:lexenv-find name funs)))))
 145                       (%coerce-name-to-fun name)
 146                       (%simple-eval original-exp lexenv))))
 147                ((quote)
 148                 (unless (= n-args 1)
 149                   (error "wrong number of args to QUOTE:~% ~S" exp))
 150                 (second exp))
 151                (setq
 152                 (unless (evenp n-args)
 153                   (error "odd number of args to SETQ:~% ~S" exp))
 154                 (unless (zerop n-args)
 155                   (do ((name (cdr exp) (cddr name)))
 156                       ((null name)
 157                        (do ((args (cdr exp) (cddr args)))
 158                            ((null (cddr args))
 159                             ;; We duplicate the call to SET so that the
 160                             ;; correct value gets returned.
 161                             (set (first args)
 162                                  (simple-eval-in-lexenv (second args) lexenv)))
 163                          (set (first args)
 164                               (simple-eval-in-lexenv (second args) lexenv))))
 165                     (let ((symbol (first name)))
 166                       (case (info :variable :kind symbol)
 167                         (:special)
 168                         (t (return (%simple-eval original-exp lexenv))))
 169                       (unless (type= (info :variable :type symbol)
 170                                      *universal-type*)
 171                         ;; let the compiler deal with type checking
 172                         (return (%simple-eval original-exp lexenv)))))))
 173                ((progn)
 174                 (simple-eval-progn-body (rest exp) lexenv))
 175                ((eval-when)
 176                 ;; FIXME: DESTRUCTURING-BIND returns ARG-COUNT-ERROR
 177                 ;; instead of PROGRAM-ERROR when there's something wrong
 178                 ;; with the syntax here (e.g. missing SITUATIONS). This
 179                 ;; could be fixed by hand-crafting clauses to catch and
 180                 ;; report each possibility, but it would probably be
 181                 ;; cleaner to write a new macro
 182                 ;; DESTRUCTURING-BIND-PROGRAM-SYNTAX which does
 183                 ;; DESTRUCTURING-BIND and promotes any mismatch to
 184                 ;; PROGRAM-ERROR, then to use it here and in (probably
 185                 ;; dozens of) other places where the same problem
 186                 ;; arises.
 187                 (destructuring-bind (eval-when situations &rest body) exp
 188                   (declare (ignore eval-when))
 189                   (multiple-value-bind (ct lt e)
 190                       (sb!c:parse-eval-when-situations situations)
 191                     ;; CLHS 3.8 - Special Operator EVAL-WHEN: The use of
 192                     ;; the situation :EXECUTE (or EVAL) controls whether
 193                     ;; evaluation occurs for other EVAL-WHEN forms; that
 194                     ;; is, those that are not top level forms, or those
 195                     ;; in code processed by EVAL or COMPILE. If the
 196                     ;; :EXECUTE situation is specified in such a form,
 197                     ;; then the body forms are processed as an implicit
 198                     ;; PROGN; otherwise, the EVAL-WHEN form returns NIL.
 199                     (declare (ignore ct lt))
 200                     (when e
 201                       (simple-eval-progn-body body lexenv)))))
 202                ((locally)
 203                 (simple-eval-locally exp lexenv))
 204                ((macrolet)
 205                 (destructuring-bind (definitions &rest body)
 206                     (rest exp)
 207                   (let ((lexenv
 208                          (let ((sb!c:*lexenv* lexenv))
 209                            (sb!c::funcall-in-macrolet-lexenv
 210                             definitions
 211                             (lambda (&key funs)
 212                               (declare (ignore funs))
 213                               sb!c:*lexenv*)
 214                             :eval))))
 215                     (simple-eval-locally `(locally ,@body) lexenv))))
 216                ((symbol-macrolet)
 217                 (destructuring-bind (definitions &rest body) (rest exp)
 218                   (multiple-value-bind (lexenv vars)
 219                       (let ((sb!c:*lexenv* lexenv))
 220                         (sb!c::funcall-in-symbol-macrolet-lexenv
 221                          definitions
 222                          (lambda (&key vars)
 223                            (values sb!c:*lexenv* vars))
 224                          :eval))
 225                     (simple-eval-locally `(locally ,@body) lexenv :vars vars))))
 226                ((if)
 227                 (destructuring-bind (test then &optional else) (rest exp)
 228                   (eval-in-lexenv (if (eval-in-lexenv test lexenv)
 229                                       then
 230                                       else)
 231                                   lexenv)))
 232                ((let let*)
 233                 (destructuring-bind (definitions &rest body) (rest exp)
 234                   (if (null definitions)
 235                       (simple-eval-locally `(locally ,@body) lexenv)
 236                       (%simple-eval exp lexenv))))
 237                (t
 238                 (if (and (symbolp name)
 239                          (eq (info :function :kind name) :function))
 240                     (collect ((args))
 241                       (dolist (arg (rest exp))
 242                         (args (eval-in-lexenv arg lexenv)))
 243                       (apply (symbol-function name) (args)))
 244                     (%simple-eval exp lexenv))))))
 245           (t
 246            exp))))))
 247
 248 (defun eval-in-lexenv (exp lexenv)
 249   #!+sb-eval
 250   (if (eq *evaluator-mode* :compile)
 251       (simple-eval-in-lexenv exp lexenv)
 252       (sb!eval:eval-in-native-environment exp lexenv))
 253   #!-sb-eval
 254   (simple-eval-in-lexenv exp lexenv))
 255
 256 (defun eval (original-exp)
 257   #!+sb-doc
 258   "Evaluate the argument in a null lexical environment, returning the
 259    result or results."
 260   (eval-in-lexenv original-exp (make-null-lexenv)))
 261
 262 \f
 263 ;;; miscellaneous full function definitions of things which are
 264 ;;; ordinarily handled magically by the compiler
 265
 266 (defun apply (function arg &rest arguments)
 267   #!+sb-doc
 268   "Apply FUNCTION to a list of arguments produced by evaluating ARGUMENTS in
 269   the manner of LIST*. That is, a list is made of the values of all but the
 270   last argument, appended to the value of the last argument, which must be a
 271   list."
 272   (cond ((atom arguments)
 273          (apply function arg))
 274         ((atom (cdr arguments))
 275          (apply function (cons arg (car arguments))))
 276         (t (do* ((a1 arguments a2)
 277                  (a2 (cdr arguments) (cdr a2)))
 278                 ((atom (cdr a2))
 279                  (rplacd a1 (car a2))
 280                  (apply function (cons arg arguments)))))))
 281
 282 (defun funcall (function &rest arguments)
 283   #!+sb-doc
 284   "Call FUNCTION with the given ARGUMENTS."
 285   (apply function arguments))
 286
 287 (defun values (&rest values)
 288   #!+sb-doc
 289   "Return all arguments, in order, as values."
 290   (declare (dynamic-extent values))
 291   (values-list values))
 292
 293 (defun values-list (list)
 294   #!+sb-doc
 295   "Return all of the elements of LIST, in order, as values."
 296   (values-list list))