File:  [gforth] / gforth / glocals.fs
Revision 1.41: download - view: text, annotated - select for diffs
Mon May 3 09:46:20 1999 UTC (22 years, 7 months ago) by jwilke
Branches: MAIN
CVS tags: HEAD
kernel/special.fs
	added exit-like in DOES> statement *bugfix*
glocals.fs
	used mappedwordlist constructor

    1: \ A powerful locals implementation
    2: 
    3: \ Copyright (C) 1995,1996,1997,1998 Free Software Foundation, Inc.
    4: 
    5: \ This file is part of Gforth.
    6: 
    7: \ Gforth is free software; you can redistribute it and/or
    8: \ modify it under the terms of the GNU General Public License
    9: \ as published by the Free Software Foundation; either version 2
   10: \ of the License, or (at your option) any later version.
   11: 
   12: \ This program is distributed in the hope that it will be useful,
   13: \ but WITHOUT ANY WARRANTY; without even the implied warranty of
   14: \ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   15: \ GNU General Public License for more details.
   16: 
   17: \ You should have received a copy of the GNU General Public License
   18: \ along with this program; if not, write to the Free Software
   19: \ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   20: 
   21: 
   22: \ More documentation can be found in the manual and in
   23: \ http://www.complang.tuwien.ac.at/papers/ertl94l.ps.gz
   24: 
   25: \ Local variables are quite important for writing readable programs, but
   26: \ IMO (anton) they are the worst part of the standard. There they are very
   27: \ restricted and have an ugly interface.
   28: 
   29: \ So, we implement the locals wordset, but do not recommend using
   30: \ locals-ext (which is a really bad user interface for locals).
   31: 
   32: \ We also have a nice and powerful user-interface for locals: locals are
   33: \ defined with
   34: 
   35: \ { local1 local2 ... }
   36: \ or
   37: \ { local1 local2 ... -- ... }
   38: \ (anything after the -- is just a comment)
   39: 
   40: \ Every local in this list consists of an optional type specification
   41: \ and a name. If there is only the name, it stands for a cell-sized
   42: \ value (i.e., you get the value of the local variable, not it's
   43: \ address). The following type specifiers stand before the name:
   44: 
   45: \ Specifier	Type	Access
   46: \ W:		Cell	value
   47: \ W^		Cell	address
   48: \ D:		Double	value
   49: \ D^		Double	address
   50: \ F:		Float	value
   51: \ F^		Float	address
   52: \ C:		Char	value
   53: \ C^		Char	address
   54: 
   55: \ The local variables are initialized with values from the appropriate
   56: \ stack. In contrast to the examples in the standard document our locals
   57: \ take the arguments in the expected way: The last local gets the top of
   58: \ stack, the second last gets the second stack item etc. An example:
   59: 
   60: \ : CX* { F: Ar  F: Ai  F: Br  F: Bi -- Cr Ci }
   61: \ \ complex multiplication
   62: \  Ar Br f* Ai Bi f* f-
   63: \  Ar Bi f* Ai Br f* f+ ;
   64: 
   65: \ There will also be a way to add user types, but it is not yet decided,
   66: \ how. Ideas are welcome.
   67: 
   68: \ Locals defined in this manner live until (!! see below). 
   69: \ Their names can be used during this time to get
   70: \ their value or address; The addresses produced in this way become
   71: \ invalid at the end of the lifetime.
   72: 
   73: \ Values can be changed with TO, but this is not recomended (TO is a
   74: \ kludge and words lose the single-assignment property, which makes them
   75: \ harder to analyse).
   76: 
   77: \ As for the internals, we use a special locals stack. This eliminates
   78: \ the problems and restrictions of reusing the return stack and allows
   79: \ to store floats as locals: the return stack is not guaranteed to be
   80: \ aligned correctly, but our locals stack must be float-aligned between
   81: \ words.
   82: 
   83: \ Other things about the internals are pretty unclear now.
   84: 
   85: \ Currently locals may only be
   86: \ defined at the outer level and TO is not supported.
   87: 
   88: require search.fs
   89: require float.fs
   90: 
   91: : compile-@local ( n -- ) \ gforth compile-fetch-local
   92:  case
   93:     0       of postpone @local0 endof
   94:     1 cells of postpone @local1 endof
   95:     2 cells of postpone @local2 endof
   96:     3 cells of postpone @local3 endof
   97:    ( otherwise ) dup postpone @local# ,
   98:  endcase ;
   99: 
  100: : compile-f@local ( n -- ) \ gforth compile-f-fetch-local
  101:  case
  102:     0        of postpone f@local0 endof
  103:     1 floats of postpone f@local1 endof
  104:    ( otherwise ) dup postpone f@local# ,
  105:  endcase ;
  106: 
  107: \ locals stuff needed for control structures
  108: 
  109: : compile-lp+! ( n -- ) \ gforth	compile-l-p-plus-store
  110:     dup negate locals-size +!
  111:     0 over = if
  112:     else -1 cells  over = if postpone lp-
  113:     else  1 floats over = if postpone lp+
  114:     else  2 floats over = if postpone lp+2
  115:     else postpone lp+!# dup ,
  116:     then then then then drop ;
  117: 
  118: : adjust-locals-size ( n -- ) \ gforth
  119:     \ sets locals-size to n and generates an appropriate lp+!
  120:     locals-size @ swap - compile-lp+! ;
  121: 
  122: \ the locals stack grows downwards (see primitives)
  123: \ of the local variables of a group (in braces) the leftmost is on top,
  124: \ i.e. by going onto the locals stack the order is reversed.
  125: \ there are alignment gaps if necessary.
  126: \ lp must have the strictest alignment (usually float) across calls;
  127: \ for simplicity we align it strictly for every group.
  128: 
  129: slowvoc @
  130: slowvoc on \ we want a linked list for the vocabulary locals
  131: vocabulary locals \ this contains the local variables
  132: ' locals >body wordlist-id ' locals-list >body !
  133: slowvoc !
  134: 
  135: create locals-buffer 1000 allot \ !! limited and unsafe
  136:     \ here the names of the local variables are stored
  137:     \ we would have problems storing them at the normal dp
  138: 
  139: variable locals-dp \ so here's the special dp for locals.
  140: 
  141: : alignlp-w ( n1 -- n2 )
  142:     \ cell-align size and generate the corresponding code for aligning lp
  143:     aligned dup adjust-locals-size ;
  144: 
  145: : alignlp-f ( n1 -- n2 )
  146:     faligned dup adjust-locals-size ;
  147: 
  148: \ a local declaration group (the braces stuff) is compiled by calling
  149: \ the appropriate compile-pushlocal for the locals, starting with the
  150: \ righmost local; the names are already created earlier, the
  151: \ compile-pushlocal just inserts the offsets from the frame base.
  152: 
  153: : compile-pushlocal-w ( a-addr -- ) ( run-time: w -- )
  154: \ compiles a push of a local variable, and adjusts locals-size
  155: \ stores the offset of the local variable to a-addr
  156:     locals-size @ alignlp-w cell+ dup locals-size !
  157:     swap !
  158:     postpone >l ;
  159: 
  160: \ locals list operations
  161: 
  162: : common-list ( list1 list2 -- list3 ) \ gforth-internal
  163: \ list1 and list2 are lists, where the heads are at higher addresses than
  164: \ the tail. list3 is the largest sublist of both lists.
  165:  begin
  166:    2dup u<>
  167:  while
  168:    2dup u>
  169:    if
  170:      swap
  171:    then
  172:    @
  173:  repeat
  174:  drop ;
  175: 
  176: : sub-list? ( list1 list2 -- f ) \ gforth-internal
  177: \ true iff list1 is a sublist of list2
  178:  begin
  179:    2dup u<
  180:  while
  181:    @
  182:  repeat
  183:  = ;
  184: 
  185: : list-size ( list -- u ) \ gforth-internal
  186:     \ size of the locals frame represented by list
  187:     0 ( list n )
  188:     begin
  189: 	over 0<>
  190:     while
  191: 	over
  192: 	((name>)) >body @ max
  193: 	swap @ swap ( get next )
  194:     repeat
  195:     faligned nip ;
  196: 
  197: : set-locals-size-list ( list -- )
  198:     dup locals-list !
  199:     list-size locals-size ! ;
  200: 
  201: : check-begin ( list -- )
  202: \ warn if list is not a sublist of locals-list
  203:  locals-list @ sub-list? 0= if
  204:    \ !! print current position
  205:    ." compiler was overly optimistic about locals at a BEGIN" cr
  206:    \ !! print assumption and reality
  207:  then ;
  208: 
  209: : compile-pushlocal-f ( a-addr -- ) ( run-time: f -- )
  210:     locals-size @ alignlp-f float+ dup locals-size !
  211:     swap !
  212:     postpone f>l ;
  213: 
  214: : compile-pushlocal-d ( a-addr -- ) ( run-time: w1 w2 -- )
  215:     locals-size @ alignlp-w cell+ cell+ dup locals-size !
  216:     swap !
  217:     postpone swap postpone >l postpone >l ;
  218: 
  219: : compile-pushlocal-c ( a-addr -- ) ( run-time: w -- )
  220:     -1 chars compile-lp+!
  221:     locals-size @ swap !
  222:     postpone lp@ postpone c! ;
  223: 
  224: : create-local ( " name" -- a-addr )
  225:     \ defines the local "name"; the offset of the local shall be
  226:     \ stored in a-addr
  227:     create
  228: 	immediate restrict
  229: 	here 0 , ( place for the offset ) ;
  230: 
  231: : lp-offset ( n1 -- n2 )
  232: \ converts the offset from the frame start to an offset from lp and
  233: \ i.e., the address of the local is lp+locals_size-offset
  234:   locals-size @ swap - ;
  235: 
  236: : lp-offset, ( n -- )
  237: \ converts the offset from the frame start to an offset from lp and
  238: \ adds it as inline argument to a preceding locals primitive
  239:   lp-offset , ;
  240: 
  241: vocabulary locals-types \ this contains all the type specifyers, -- and }
  242: locals-types definitions
  243: 
  244: : W: ( "name" -- a-addr xt ) \ gforth w-colon
  245:     create-local
  246: 	\ xt produces the appropriate locals pushing code when executed
  247: 	['] compile-pushlocal-w
  248:     does> ( Compilation: -- ) ( Run-time: -- w )
  249:         \ compiles a local variable access
  250: 	@ lp-offset compile-@local ;
  251: 
  252: : W^ ( "name" -- a-addr xt ) \ gforth w-caret
  253:     create-local
  254: 	['] compile-pushlocal-w
  255:     does> ( Compilation: -- ) ( Run-time: -- w )
  256: 	postpone laddr# @ lp-offset, ;
  257: 
  258: : F: ( "name" -- a-addr xt ) \ gforth f-colon
  259:     create-local
  260: 	['] compile-pushlocal-f
  261:     does> ( Compilation: -- ) ( Run-time: -- w )
  262: 	@ lp-offset compile-f@local ;
  263: 
  264: : F^ ( "name" -- a-addr xt ) \ gforth f-caret
  265:     create-local
  266: 	['] compile-pushlocal-f
  267:     does> ( Compilation: -- ) ( Run-time: -- w )
  268: 	postpone laddr# @ lp-offset, ;
  269: 
  270: : D: ( "name" -- a-addr xt ) \ gforth d-colon
  271:     create-local
  272: 	['] compile-pushlocal-d
  273:     does> ( Compilation: -- ) ( Run-time: -- w )
  274: 	postpone laddr# @ lp-offset, postpone 2@ ;
  275: 
  276: : D^ ( "name" -- a-addr xt ) \ gforth d-caret
  277:     create-local
  278: 	['] compile-pushlocal-d
  279:     does> ( Compilation: -- ) ( Run-time: -- w )
  280: 	postpone laddr# @ lp-offset, ;
  281: 
  282: : C: ( "name" -- a-addr xt ) \ gforth c-colon
  283:     create-local
  284: 	['] compile-pushlocal-c
  285:     does> ( Compilation: -- ) ( Run-time: -- w )
  286: 	postpone laddr# @ lp-offset, postpone c@ ;
  287: 
  288: : C^ ( "name" -- a-addr xt ) \ gforth c-caret
  289:     create-local
  290: 	['] compile-pushlocal-c
  291:     does> ( Compilation: -- ) ( Run-time: -- w )
  292: 	postpone laddr# @ lp-offset, ;
  293: 
  294: \ you may want to make comments in a locals definitions group:
  295: ' \ alias \ ( -- ) \ core-ext,block-ext backslash
  296: \G Line comment: if @code{BLK} contains 0, parse and discard the remainder
  297: \G of the parse area. Otherwise, parse and discard all subsequent characters in the
  298: \G parse area corresponding to the current line.
  299: immediate 
  300: 
  301: ' ( alias ( ( compilation 'ccc<close-paren>' -- ; run-time -- ) \ core,file	paren
  302: \G Comment: parse and discard all subsequent characters in the parse
  303: \G area until ")" is encountered. During interactive input, an end-of-line
  304: \G also acts as a comment terminator. For file input, it does not; if the
  305: \G end-of-file is encountered whilst parsing for the ")" delimiter, Gforth
  306: \G will generate a warning.
  307: immediate
  308: 
  309: forth definitions
  310: 
  311: \ the following gymnastics are for declaring locals without type specifier.
  312: \ we exploit a feature of our dictionary: every wordlist
  313: \ has it's own methods for finding words etc.
  314: \ So we create a vocabulary new-locals, that creates a 'w:' local named x
  315: \ when it is asked if it contains x.
  316: 
  317: also locals-types
  318: 
  319: : new-locals-find ( caddr u w -- nfa )
  320: \ this is the find method of the new-locals vocabulary
  321: \ make a new local with name caddr u; w is ignored
  322: \ the returned nfa denotes a word that produces what W: produces
  323: \ !! do the whole thing without nextname
  324:     drop nextname
  325:     ['] W: >name ;
  326: 
  327: previous
  328: 
  329: : new-locals-reveal ( -- )
  330:   true abort" this should not happen: new-locals-reveal" ;
  331: 
  332: create new-locals-map ( -- wordlist-map )
  333: ' new-locals-find A,
  334: ' new-locals-reveal A,
  335: ' drop A, \ rehash method
  336: ' drop A,
  337: 
  338: new-locals-map mappedwordlist Constant new-locals-wl
  339: 
  340: \ slowvoc @
  341: \ slowvoc on
  342: \ vocabulary new-locals
  343: \ slowvoc !
  344: \ new-locals-map ' new-locals >body wordlist-map A! \ !! use special access words
  345: 
  346: variable old-dpp
  347: 
  348: \ and now, finally, the user interface words
  349: : { ( -- lastxt wid 0 ) \ gforth open-brace
  350:     dp old-dpp !
  351:     locals-dp dpp !
  352:     lastxt get-current
  353:     get-order new-locals-wl swap 1+ set-order
  354:     also locals definitions locals-types
  355:     0 TO locals-wordlist
  356:     0 postpone [ ; immediate
  357: 
  358: locals-types definitions
  359: 
  360: : } ( lastxt wid 0 a-addr1 xt1 ... -- ) \ gforth close-brace
  361:     \ ends locals definitions
  362:     ] old-dpp @ dpp !
  363:     begin
  364: 	dup
  365:     while
  366: 	execute
  367:     repeat
  368:     drop
  369:     locals-size @ alignlp-f locals-size ! \ the strictest alignment
  370:     previous previous
  371:     set-current lastcfa !
  372:     locals-list 0 wordlist-id - TO locals-wordlist ;
  373: 
  374: : -- ( addr wid 0 ... -- ) \ gforth dash-dash
  375:     }
  376:     [char] } parse 2drop ;
  377: 
  378: forth definitions
  379: 
  380: \ A few thoughts on automatic scopes for locals and how they can be
  381: \ implemented:
  382: 
  383: \ We have to combine locals with the control structures. My basic idea
  384: \ was to start the life of a local at the declaration point. The life
  385: \ would end at any control flow join (THEN, BEGIN etc.) where the local
  386: \ is lot live on both input flows (note that the local can still live in
  387: \ other, later parts of the control flow). This would make a local live
  388: \ as long as you expected and sometimes longer (e.g. a local declared in
  389: \ a BEGIN..UNTIL loop would still live after the UNTIL).
  390: 
  391: \ The following example illustrates the problems of this approach:
  392: 
  393: \ { z }
  394: \ if
  395: \   { x }
  396: \ begin
  397: \   { y }
  398: \ [ 1 cs-roll ] then
  399: \   ...
  400: \ until
  401: 
  402: \ x lives only until the BEGIN, but the compiler does not know this
  403: \ until it compiles the UNTIL (it can deduce it at the THEN, because at
  404: \ that point x lives in no thread, but that does not help much). This is
  405: \ solved by optimistically assuming at the BEGIN that x lives, but
  406: \ warning at the UNTIL that it does not. The user is then responsible
  407: \ for checking that x is only used where it lives.
  408: 
  409: \ The produced code might look like this (leaving out alignment code):
  410: 
  411: \ >l ( z )
  412: \ ?branch <then>
  413: \ >l ( x )
  414: \ <begin>:
  415: \ >l ( y )
  416: \ lp+!# 8 ( RIP: x,y )
  417: \ <then>:
  418: \ ...
  419: \ lp+!# -4 ( adjust lp to <begin> state )
  420: \ ?branch <begin>
  421: \ lp+!# 4 ( undo adjust )
  422: 
  423: \ The BEGIN problem also has another incarnation:
  424: 
  425: \ AHEAD
  426: \ BEGIN
  427: \   x
  428: \ [ 1 CS-ROLL ] THEN
  429: \   { x }
  430: \   ...
  431: \ UNTIL
  432: 
  433: \ should be legal: The BEGIN is not a control flow join in this case,
  434: \ since it cannot be entered from the top; therefore the definition of x
  435: \ dominates the use. But the compiler processes the use first, and since
  436: \ it does not look ahead to notice the definition, it will complain
  437: \ about it. Here's another variation of this problem:
  438: 
  439: \ IF
  440: \   { x }
  441: \ ELSE
  442: \   ...
  443: \ AHEAD
  444: \ BEGIN
  445: \   x
  446: \ [ 2 CS-ROLL ] THEN
  447: \   ...
  448: \ UNTIL
  449: 
  450: \ In this case x is defined before the use, and the definition dominates
  451: \ the use, but the compiler does not know this until it processes the
  452: \ UNTIL. So what should the compiler assume does live at the BEGIN, if
  453: \ the BEGIN is not a control flow join? The safest assumption would be
  454: \ the intersection of all locals lists on the control flow
  455: \ stack. However, our compiler assumes that the same variables are live
  456: \ as on the top of the control flow stack. This covers the following case:
  457: 
  458: \ { x }
  459: \ AHEAD
  460: \ BEGIN
  461: \   x
  462: \ [ 1 CS-ROLL ] THEN
  463: \   ...
  464: \ UNTIL
  465: 
  466: \ If this assumption is too optimistic, the compiler will warn the user.
  467: 
  468: \ Implementation:
  469: 
  470: \ explicit scoping
  471: 
  472: : scope ( compilation  -- scope ; run-time  -- ) \ gforth
  473:     cs-push-part scopestart ; immediate
  474: 
  475: : adjust-locals-list ( wid -- )
  476:     locals-list @ common-list
  477:     dup list-size adjust-locals-size
  478:     locals-list ! ;
  479: 
  480: : endscope ( compilation scope -- ; run-time  -- ) \ gforth
  481:     scope?
  482:     drop  adjust-locals-list ; immediate
  483: 
  484: \ adapt the hooks
  485: 
  486: : locals-:-hook ( sys -- sys addr xt n )
  487:     \ addr is the nfa of the defined word, xt its xt
  488:     DEFERS :-hook
  489:     last @ lastcfa @
  490:     clear-leave-stack
  491:     0 locals-size !
  492:     locals-buffer locals-dp !
  493:     0 locals-list !
  494:     dead-code off
  495:     defstart ;
  496: 
  497: : locals-;-hook ( sys addr xt sys -- sys )
  498:     def?
  499:     0 TO locals-wordlist
  500:     0 adjust-locals-size ( not every def ends with an exit )
  501:     lastcfa ! last !
  502:     DEFERS ;-hook ;
  503: 
  504: \ THEN (another control flow from before joins the current one):
  505: \ The new locals-list is the intersection of the current locals-list and
  506: \ the orig-local-list. The new locals-size is the (alignment-adjusted)
  507: \ size of the new locals-list. The following code is generated:
  508: \ lp+!# (current-locals-size - orig-locals-size)
  509: \ <then>:
  510: \ lp+!# (orig-locals-size - new-locals-size)
  511: 
  512: \ Of course "lp+!# 0" is not generated. Still this is admittedly a bit
  513: \ inefficient, e.g. if there is a locals declaration between IF and
  514: \ ELSE. However, if ELSE generates an appropriate "lp+!#" before the
  515: \ branch, there will be none after the target <then>.
  516: 
  517: : (then-like) ( orig -- )
  518:     dead-orig =
  519:     if
  520: 	>resolve drop
  521:     else
  522:         dead-code @
  523:         if
  524: 	    >resolve set-locals-size-list dead-code off
  525: 	else \ both live
  526: 	    over list-size adjust-locals-size
  527: 	    >resolve
  528: 	    adjust-locals-list
  529: 	then
  530:     then ;
  531: 
  532: : (begin-like) ( -- )
  533:     dead-code @ if
  534: 	\ set up an assumption of the locals visible here.  if the
  535: 	\ users want something to be visible, they have to declare
  536: 	\ that using ASSUME-LIVE
  537: 	backedge-locals @ set-locals-size-list
  538:     then
  539:     dead-code off ;
  540: 
  541: \ AGAIN (the current control flow joins another, earlier one):
  542: \ If the dest-locals-list is not a subset of the current locals-list,
  543: \ issue a warning (see below). The following code is generated:
  544: \ lp+!# (current-local-size - dest-locals-size)
  545: \ branch <begin>
  546: 
  547: : (again-like) ( dest -- addr )
  548:     over list-size adjust-locals-size
  549:     swap check-begin  POSTPONE unreachable ;
  550: 
  551: \ UNTIL (the current control flow may join an earlier one or continue):
  552: \ Similar to AGAIN. The new locals-list and locals-size are the current
  553: \ ones. The following code is generated:
  554: \ ?branch-lp+!# <begin> (current-local-size - dest-locals-size)
  555: 
  556: : (until-like) ( list addr xt1 xt2 -- )
  557:     \ list and addr are a fragment of a cs-item
  558:     \ xt1 is the conditional branch without lp adjustment, xt2 is with
  559:     >r >r
  560:     locals-size @ 2 pick list-size - dup if ( list dest-addr adjustment )
  561: 	r> drop r> compile,
  562: 	swap <resolve ( list adjustment ) ,
  563:     else ( list dest-addr adjustment )
  564: 	drop
  565: 	r> compile, <resolve
  566: 	r> drop
  567:     then ( list )
  568:     check-begin ;
  569: 
  570: : (exit-like) ( -- )
  571:     0 adjust-locals-size ;
  572: 
  573: ' locals-:-hook IS :-hook
  574: ' locals-;-hook IS ;-hook
  575: 
  576: ' (then-like)  IS then-like
  577: ' (begin-like) IS begin-like
  578: ' (again-like) IS again-like
  579: ' (until-like) IS until-like
  580: ' (exit-like)  IS exit-like
  581: 
  582: \ The words in the locals dictionary space are not deleted until the end
  583: \ of the current word. This is a bit too conservative, but very simple.
  584: 
  585: \ There are a few cases to consider: (see above)
  586: 
  587: \ after AGAIN, AHEAD, EXIT (the current control flow is dead):
  588: \ We have to special-case the above cases against that. In this case the
  589: \ things above are not control flow joins. Everything should be taken
  590: \ over from the live flow. No lp+!# is generated.
  591: 
  592: \ About warning against uses of dead locals. There are several options:
  593: 
  594: \ 1) Do not complain (After all, this is Forth;-)
  595: 
  596: \ 2) Additional restrictions can be imposed so that the situation cannot
  597: \ arise; the programmer would have to introduce explicit scoping
  598: \ declarations in cases like the above one. I.e., complain if there are
  599: \ locals that are live before the BEGIN but not before the corresponding
  600: \ AGAIN (replace DO etc. for BEGIN and UNTIL etc. for AGAIN).
  601: 
  602: \ 3) The real thing: i.e. complain, iff a local lives at a BEGIN, is
  603: \ used on a path starting at the BEGIN, and does not live at the
  604: \ corresponding AGAIN. This is somewhat hard to implement. a) How does
  605: \ the compiler know when it is working on a path starting at a BEGIN
  606: \ (consider "{ x } if begin [ 1 cs-roll ] else x endif again")? b) How
  607: \ is the usage info stored?
  608: 
  609: \ For now I'll resort to alternative 2. When it produces warnings they
  610: \ will often be spurious, but warnings should be rare. And better
  611: \ spurious warnings now and then than days of bug-searching.
  612: 
  613: \ Explicit scoping of locals is implemented by cs-pushing the current
  614: \ locals-list and -size (and an unused cell, to make the size equal to
  615: \ the other entries) at the start of the scope, and restoring them at
  616: \ the end of the scope to the intersection, like THEN does.
  617: 
  618: 
  619: \ And here's finally the ANS standard stuff
  620: 
  621: : (local) ( addr u -- ) \ local paren-local-paren
  622:     \ a little space-inefficient, but well deserved ;-)
  623:     \ In exchange, there are no restrictions whatsoever on using (local)
  624:     \ as long as you use it in a definition
  625:     dup
  626:     if
  627: 	nextname POSTPONE { [ also locals-types ] W: } [ previous ]
  628:     else
  629: 	2drop
  630:     endif ;
  631: 
  632: : >definer ( xt -- definer )
  633:     \ this gives a unique identifier for the way the xt was defined
  634:     \ words defined with different does>-codes have different definers
  635:     \ the definer can be used for comparison and in definer!
  636:     dup >does-code
  637:     ?dup-if
  638: 	nip 1 or
  639:     else
  640: 	>code-address
  641:     then ;
  642: 
  643: : definer! ( definer xt -- )
  644:     \ gives the word represented by xt the behaviour associated with definer
  645:     over 1 and if
  646: 	swap [ 1 invert ] literal and does-code!
  647:     else
  648: 	code-address!
  649:     then ;
  650: 
  651: :noname
  652:     ' dup >definer [ ' locals-wordlist ] literal >definer =
  653:     if
  654: 	>body !
  655:     else
  656: 	-&32 throw
  657:     endif ;
  658: :noname
  659:     0 0 0. 0.0e0 { c: clocal w: wlocal d: dlocal f: flocal }
  660:     comp' drop dup >definer
  661:     case
  662: 	[ ' locals-wordlist ] literal >definer \ value
  663: 	OF >body POSTPONE Aliteral POSTPONE ! ENDOF
  664: 	\ !! dependent on c: etc. being does>-defining words
  665: 	\ this works, because >definer uses >does-code in this case,
  666: 	\ which produces a relocatable address
  667: 	[ comp' clocal drop >definer ] literal
  668: 	OF POSTPONE laddr# >body @ lp-offset, POSTPONE c! ENDOF
  669: 	[ comp' wlocal drop >definer ] literal
  670: 	OF POSTPONE laddr# >body @ lp-offset, POSTPONE ! ENDOF
  671: 	[ comp' dlocal drop >definer ] literal
  672: 	OF POSTPONE laddr# >body @ lp-offset, POSTPONE 2! ENDOF
  673: 	[ comp' flocal drop >definer ] literal
  674: 	OF POSTPONE laddr# >body @ lp-offset, POSTPONE f! ENDOF
  675: 	-&32 throw
  676:     endcase ;
  677: interpret/compile: TO ( c|w|d|r "name" -- ) \ core-ext,local
  678: 
  679: : locals|
  680:     \ don't use 'locals|'! use '{'! A portable and free '{'
  681:     \ implementation is compat/anslocals.fs
  682:     BEGIN
  683: 	name 2dup s" |" compare 0<>
  684:     WHILE
  685: 	(local)
  686:     REPEAT
  687:     drop 0 (local) ; immediate restrict

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