Annotation of gforth/glocals.fs, revision 1.16

1.15      anton       1: \ A powerful locals implementation
                      2: 
                      3: \ Copyright (C) 1995 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: 
1.16    ! anton      22: \ More documentation can be found in the manual and in
        !            23: \ http://www.complang.tuwien.ac.at/papers/ertl94l.ps.gz
        !            24: 
1.1       anton      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: 
1.14      anton      88: require search-order.fs
                     89: require float.fs
1.1       anton      90: 
1.14      anton      91: : compile-@local ( n -- ) \ gforth compile-fetch-local
1.3       anton      92:  case
1.7       pazsan     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
1.3       anton      97:    ( otherwise ) dup postpone @local# ,
                     98:  endcase ;
                     99: 
1.14      anton     100: : compile-f@local ( n -- ) \ gforth compile-f-fetch-local
1.3       anton     101:  case
1.7       pazsan    102:     0        of postpone f@local0 endof
                    103:     1 floats of postpone f@local1 endof
1.3       anton     104:    ( otherwise ) dup postpone f@local# ,
                    105:  endcase ;
                    106: 
1.1       anton     107: \ the locals stack grows downwards (see primitives)
                    108: \ of the local variables of a group (in braces) the leftmost is on top,
                    109: \ i.e. by going onto the locals stack the order is reversed.
                    110: \ there are alignment gaps if necessary.
                    111: \ lp must have the strictest alignment (usually float) across calls;
                    112: \ for simplicity we align it strictly for every group.
                    113: 
1.5       anton     114: slowvoc @
                    115: slowvoc on \ we want a linked list for the vocabulary locals
1.1       anton     116: vocabulary locals \ this contains the local variables
1.3       anton     117: ' locals >body ' locals-list >body !
1.5       anton     118: slowvoc !
1.1       anton     119: 
                    120: create locals-buffer 1000 allot \ !! limited and unsafe
                    121:     \ here the names of the local variables are stored
                    122:     \ we would have problems storing them at the normal dp
                    123: 
                    124: variable locals-dp \ so here's the special dp for locals.
                    125: 
                    126: : alignlp-w ( n1 -- n2 )
                    127:     \ cell-align size and generate the corresponding code for aligning lp
1.3       anton     128:     aligned dup adjust-locals-size ;
1.1       anton     129: 
                    130: : alignlp-f ( n1 -- n2 )
1.3       anton     131:     faligned dup adjust-locals-size ;
1.1       anton     132: 
                    133: \ a local declaration group (the braces stuff) is compiled by calling
                    134: \ the appropriate compile-pushlocal for the locals, starting with the
                    135: \ righmost local; the names are already created earlier, the
                    136: \ compile-pushlocal just inserts the offsets from the frame base.
                    137: 
                    138: : compile-pushlocal-w ( a-addr -- ) ( run-time: w -- )
                    139: \ compiles a push of a local variable, and adjusts locals-size
                    140: \ stores the offset of the local variable to a-addr
                    141:     locals-size @ alignlp-w cell+ dup locals-size !
                    142:     swap !
                    143:     postpone >l ;
                    144: 
                    145: : compile-pushlocal-f ( a-addr -- ) ( run-time: f -- )
                    146:     locals-size @ alignlp-f float+ dup locals-size !
                    147:     swap !
                    148:     postpone f>l ;
                    149: 
                    150: : compile-pushlocal-d ( a-addr -- ) ( run-time: w1 w2 -- )
                    151:     locals-size @ alignlp-w cell+ cell+ dup locals-size !
                    152:     swap !
                    153:     postpone swap postpone >l postpone >l ;
                    154: 
                    155: : compile-pushlocal-c ( a-addr -- ) ( run-time: w -- )
1.3       anton     156:     -1 chars compile-lp+!
1.1       anton     157:     locals-size @ swap !
                    158:     postpone lp@ postpone c! ;
                    159: 
                    160: : create-local ( " name" -- a-addr )
1.9       anton     161:     \ defines the local "name"; the offset of the local shall be
                    162:     \ stored in a-addr
1.1       anton     163:     create
1.12      anton     164:        immediate restrict
1.1       anton     165:        here 0 , ( place for the offset ) ;
                    166: 
1.3       anton     167: : lp-offset ( n1 -- n2 )
                    168: \ converts the offset from the frame start to an offset from lp and
                    169: \ i.e., the address of the local is lp+locals_size-offset
                    170:   locals-size @ swap - ;
                    171: 
1.1       anton     172: : lp-offset, ( n -- )
                    173: \ converts the offset from the frame start to an offset from lp and
                    174: \ adds it as inline argument to a preceding locals primitive
1.3       anton     175:   lp-offset , ;
1.1       anton     176: 
                    177: vocabulary locals-types \ this contains all the type specifyers, -- and }
                    178: locals-types definitions
                    179: 
1.14      anton     180: : W: ( "name" -- a-addr xt ) \ gforth w-colon
                    181:     create-local
1.1       anton     182:        \ xt produces the appropriate locals pushing code when executed
                    183:        ['] compile-pushlocal-w
                    184:     does> ( Compilation: -- ) ( Run-time: -- w )
                    185:         \ compiles a local variable access
1.3       anton     186:        @ lp-offset compile-@local ;
1.1       anton     187: 
1.14      anton     188: : W^ ( "name" -- a-addr xt ) \ gforth w-caret
                    189:     create-local
1.1       anton     190:        ['] compile-pushlocal-w
                    191:     does> ( Compilation: -- ) ( Run-time: -- w )
                    192:        postpone laddr# @ lp-offset, ;
                    193: 
1.14      anton     194: : F: ( "name" -- a-addr xt ) \ gforth f-colon
                    195:     create-local
1.1       anton     196:        ['] compile-pushlocal-f
                    197:     does> ( Compilation: -- ) ( Run-time: -- w )
1.3       anton     198:        @ lp-offset compile-f@local ;
1.1       anton     199: 
1.14      anton     200: : F^ ( "name" -- a-addr xt ) \ gforth f-caret
                    201:     create-local
1.1       anton     202:        ['] compile-pushlocal-f
                    203:     does> ( Compilation: -- ) ( Run-time: -- w )
                    204:        postpone laddr# @ lp-offset, ;
                    205: 
1.14      anton     206: : D: ( "name" -- a-addr xt ) \ gforth d-colon
                    207:     create-local
1.1       anton     208:        ['] compile-pushlocal-d
                    209:     does> ( Compilation: -- ) ( Run-time: -- w )
                    210:        postpone laddr# @ lp-offset, postpone 2@ ;
                    211: 
1.14      anton     212: : D^ ( "name" -- a-addr xt ) \ gforth d-caret
                    213:     create-local
1.1       anton     214:        ['] compile-pushlocal-d
                    215:     does> ( Compilation: -- ) ( Run-time: -- w )
                    216:        postpone laddr# @ lp-offset, ;
                    217: 
1.14      anton     218: : C: ( "name" -- a-addr xt ) \ gforth c-colon
                    219:     create-local
1.1       anton     220:        ['] compile-pushlocal-c
                    221:     does> ( Compilation: -- ) ( Run-time: -- w )
                    222:        postpone laddr# @ lp-offset, postpone c@ ;
                    223: 
1.14      anton     224: : C^ ( "name" -- a-addr xt ) \ gforth c-caret
                    225:     create-local
1.1       anton     226:        ['] compile-pushlocal-c
                    227:     does> ( Compilation: -- ) ( Run-time: -- w )
                    228:        postpone laddr# @ lp-offset, ;
                    229: 
                    230: \ you may want to make comments in a locals definitions group:
                    231: ' \ alias \ immediate
                    232: ' ( alias ( immediate
                    233: 
                    234: forth definitions
                    235: 
                    236: \ the following gymnastics are for declaring locals without type specifier.
                    237: \ we exploit a feature of our dictionary: every wordlist
                    238: \ has it's own methods for finding words etc.
                    239: \ So we create a vocabulary new-locals, that creates a 'w:' local named x
                    240: \ when it is asked if it contains x.
                    241: 
                    242: also locals-types
                    243: 
                    244: : new-locals-find ( caddr u w -- nfa )
                    245: \ this is the find method of the new-locals vocabulary
                    246: \ make a new local with name caddr u; w is ignored
                    247: \ the returned nfa denotes a word that produces what W: produces
                    248: \ !! do the whole thing without nextname
1.3       anton     249:     drop nextname
                    250:     ['] W: >name ;
1.1       anton     251: 
                    252: previous
                    253: 
                    254: : new-locals-reveal ( -- )
                    255:   true abort" this should not happen: new-locals-reveal" ;
                    256: 
                    257: create new-locals-map ' new-locals-find A, ' new-locals-reveal A,
                    258: 
                    259: vocabulary new-locals
                    260: new-locals-map ' new-locals >body cell+ A! \ !! use special access words
                    261: 
                    262: variable old-dpp
                    263: 
                    264: \ and now, finally, the user interface words
1.14      anton     265: : { ( -- addr wid 0 ) \ gforth open-brace
1.1       anton     266:     dp old-dpp !
                    267:     locals-dp dpp !
                    268:     also new-locals
                    269:     also get-current locals definitions  locals-types
                    270:     0 TO locals-wordlist
                    271:     0 postpone [ ; immediate
                    272: 
                    273: locals-types definitions
                    274: 
1.14      anton     275: : } ( addr wid 0 a-addr1 xt1 ... -- ) \ gforth close-brace
1.1       anton     276:     \ ends locals definitions
                    277:     ] old-dpp @ dpp !
                    278:     begin
                    279:        dup
                    280:     while
                    281:        execute
                    282:     repeat
                    283:     drop
                    284:     locals-size @ alignlp-f locals-size ! \ the strictest alignment
                    285:     set-current
                    286:     previous previous
                    287:     locals-list TO locals-wordlist ;
                    288: 
1.14      anton     289: : -- ( addr wid 0 ... -- ) \ gforth dash-dash
1.1       anton     290:     }
1.9       anton     291:     [char] } parse 2drop ;
1.1       anton     292: 
                    293: forth definitions
                    294: 
                    295: \ A few thoughts on automatic scopes for locals and how they can be
                    296: \ implemented:
                    297: 
                    298: \ We have to combine locals with the control structures. My basic idea
                    299: \ was to start the life of a local at the declaration point. The life
                    300: \ would end at any control flow join (THEN, BEGIN etc.) where the local
                    301: \ is lot live on both input flows (note that the local can still live in
                    302: \ other, later parts of the control flow). This would make a local live
                    303: \ as long as you expected and sometimes longer (e.g. a local declared in
                    304: \ a BEGIN..UNTIL loop would still live after the UNTIL).
                    305: 
                    306: \ The following example illustrates the problems of this approach:
                    307: 
                    308: \ { z }
                    309: \ if
                    310: \   { x }
                    311: \ begin
                    312: \   { y }
                    313: \ [ 1 cs-roll ] then
                    314: \   ...
                    315: \ until
                    316: 
                    317: \ x lives only until the BEGIN, but the compiler does not know this
                    318: \ until it compiles the UNTIL (it can deduce it at the THEN, because at
                    319: \ that point x lives in no thread, but that does not help much). This is
                    320: \ solved by optimistically assuming at the BEGIN that x lives, but
                    321: \ warning at the UNTIL that it does not. The user is then responsible
                    322: \ for checking that x is only used where it lives.
                    323: 
                    324: \ The produced code might look like this (leaving out alignment code):
                    325: 
                    326: \ >l ( z )
                    327: \ ?branch <then>
                    328: \ >l ( x )
                    329: \ <begin>:
                    330: \ >l ( y )
                    331: \ lp+!# 8 ( RIP: x,y )
                    332: \ <then>:
                    333: \ ...
                    334: \ lp+!# -4 ( adjust lp to <begin> state )
                    335: \ ?branch <begin>
                    336: \ lp+!# 4 ( undo adjust )
                    337: 
                    338: \ The BEGIN problem also has another incarnation:
                    339: 
                    340: \ AHEAD
                    341: \ BEGIN
                    342: \   x
                    343: \ [ 1 CS-ROLL ] THEN
                    344: \   { x }
                    345: \   ...
                    346: \ UNTIL
                    347: 
                    348: \ should be legal: The BEGIN is not a control flow join in this case,
                    349: \ since it cannot be entered from the top; therefore the definition of x
                    350: \ dominates the use. But the compiler processes the use first, and since
                    351: \ it does not look ahead to notice the definition, it will complain
                    352: \ about it. Here's another variation of this problem:
                    353: 
                    354: \ IF
                    355: \   { x }
                    356: \ ELSE
                    357: \   ...
                    358: \ AHEAD
                    359: \ BEGIN
                    360: \   x
                    361: \ [ 2 CS-ROLL ] THEN
                    362: \   ...
                    363: \ UNTIL
                    364: 
                    365: \ In this case x is defined before the use, and the definition dominates
                    366: \ the use, but the compiler does not know this until it processes the
                    367: \ UNTIL. So what should the compiler assume does live at the BEGIN, if
                    368: \ the BEGIN is not a control flow join? The safest assumption would be
                    369: \ the intersection of all locals lists on the control flow
                    370: \ stack. However, our compiler assumes that the same variables are live
                    371: \ as on the top of the control flow stack. This covers the following case:
                    372: 
                    373: \ { x }
                    374: \ AHEAD
                    375: \ BEGIN
                    376: \   x
                    377: \ [ 1 CS-ROLL ] THEN
                    378: \   ...
                    379: \ UNTIL
                    380: 
                    381: \ If this assumption is too optimistic, the compiler will warn the user.
                    382: 
1.3       anton     383: \ Implementation: migrated to kernal.fs
1.1       anton     384: 
                    385: \ THEN (another control flow from before joins the current one):
                    386: \ The new locals-list is the intersection of the current locals-list and
                    387: \ the orig-local-list. The new locals-size is the (alignment-adjusted)
                    388: \ size of the new locals-list. The following code is generated:
                    389: \ lp+!# (current-locals-size - orig-locals-size)
                    390: \ <then>:
                    391: \ lp+!# (orig-locals-size - new-locals-size)
                    392: 
                    393: \ Of course "lp+!# 0" is not generated. Still this is admittedly a bit
                    394: \ inefficient, e.g. if there is a locals declaration between IF and
                    395: \ ELSE. However, if ELSE generates an appropriate "lp+!#" before the
                    396: \ branch, there will be none after the target <then>.
                    397: 
1.3       anton     398: \ explicit scoping
1.1       anton     399: 
1.14      anton     400: : scope ( compilation  -- scope ; run-time  -- ) \ gforth
1.3       anton     401:  cs-push-part scopestart ; immediate
                    402: 
1.14      anton     403: : endscope ( compilation scope -- ; run-time  -- ) \ gforth
1.3       anton     404:  scope?
1.1       anton     405:  drop
1.3       anton     406:  locals-list @ common-list
                    407:  dup list-size adjust-locals-size
                    408:  locals-list ! ; immediate
1.1       anton     409: 
1.3       anton     410: \ adapt the hooks
1.1       anton     411: 
1.3       anton     412: : locals-:-hook ( sys -- sys addr xt n )
                    413:     \ addr is the nfa of the defined word, xt its xt
1.1       anton     414:     DEFERS :-hook
                    415:     last @ lastcfa @
                    416:     clear-leave-stack
                    417:     0 locals-size !
                    418:     locals-buffer locals-dp !
1.3       anton     419:     0 locals-list !
                    420:     dead-code off
                    421:     defstart ;
1.1       anton     422: 
1.3       anton     423: : locals-;-hook ( sys addr xt sys -- sys )
                    424:     def?
1.1       anton     425:     0 TO locals-wordlist
1.3       anton     426:     0 adjust-locals-size ( not every def ends with an exit )
1.1       anton     427:     lastcfa ! last !
                    428:     DEFERS ;-hook ;
                    429: 
                    430: ' locals-:-hook IS :-hook
                    431: ' locals-;-hook IS ;-hook
                    432: 
                    433: \ The words in the locals dictionary space are not deleted until the end
                    434: \ of the current word. This is a bit too conservative, but very simple.
                    435: 
                    436: \ There are a few cases to consider: (see above)
                    437: 
                    438: \ after AGAIN, AHEAD, EXIT (the current control flow is dead):
                    439: \ We have to special-case the above cases against that. In this case the
                    440: \ things above are not control flow joins. Everything should be taken
                    441: \ over from the live flow. No lp+!# is generated.
                    442: 
                    443: \ !! The lp gymnastics for UNTIL are also a real problem: locals cannot be
                    444: \ used in signal handlers (or anything else that may be called while
                    445: \ locals live beyond the lp) without changing the locals stack.
                    446: 
                    447: \ About warning against uses of dead locals. There are several options:
                    448: 
                    449: \ 1) Do not complain (After all, this is Forth;-)
                    450: 
                    451: \ 2) Additional restrictions can be imposed so that the situation cannot
                    452: \ arise; the programmer would have to introduce explicit scoping
                    453: \ declarations in cases like the above one. I.e., complain if there are
                    454: \ locals that are live before the BEGIN but not before the corresponding
                    455: \ AGAIN (replace DO etc. for BEGIN and UNTIL etc. for AGAIN).
                    456: 
                    457: \ 3) The real thing: i.e. complain, iff a local lives at a BEGIN, is
                    458: \ used on a path starting at the BEGIN, and does not live at the
                    459: \ corresponding AGAIN. This is somewhat hard to implement. a) How does
                    460: \ the compiler know when it is working on a path starting at a BEGIN
                    461: \ (consider "{ x } if begin [ 1 cs-roll ] else x endif again")? b) How
                    462: \ is the usage info stored?
                    463: 
                    464: \ For now I'll resort to alternative 2. When it produces warnings they
                    465: \ will often be spurious, but warnings should be rare. And better
                    466: \ spurious warnings now and then than days of bug-searching.
                    467: 
                    468: \ Explicit scoping of locals is implemented by cs-pushing the current
                    469: \ locals-list and -size (and an unused cell, to make the size equal to
                    470: \ the other entries) at the start of the scope, and restoring them at
                    471: \ the end of the scope to the intersection, like THEN does.
                    472: 
                    473: 
                    474: \ And here's finally the ANS standard stuff
                    475: 
1.14      anton     476: : (local) ( addr u -- ) \ local paren-local-paren
1.3       anton     477:     \ a little space-inefficient, but well deserved ;-)
                    478:     \ In exchange, there are no restrictions whatsoever on using (local)
1.4       anton     479:     \ as long as you use it in a definition
1.3       anton     480:     dup
                    481:     if
                    482:        nextname POSTPONE { [ also locals-types ] W: } [ previous ]
                    483:     else
                    484:        2drop
                    485:     endif ;
1.1       anton     486: 
1.4       anton     487: : >definer ( xt -- definer )
                    488:     \ this gives a unique identifier for the way the xt was defined
                    489:     \ words defined with different does>-codes have different definers
                    490:     \ the definer can be used for comparison and in definer!
                    491:     dup >code-address [ ' bits >code-address ] Literal =
                    492:     \ !! this definition will not work on some implementations for `bits'
                    493:     if  \ if >code-address delivers the same value for all does>-def'd words
                    494:        >does-code 1 or \ bit 0 marks special treatment for does codes
                    495:     else
                    496:        >code-address
                    497:     then ;
                    498: 
                    499: : definer! ( definer xt -- )
                    500:     \ gives the word represented by xt the behaviour associated with definer
                    501:     over 1 and if
1.13      anton     502:        swap [ 1 invert ] literal and does-code!
1.4       anton     503:     else
                    504:        code-address!
                    505:     then ;
                    506: 
                    507: \ !! untested
1.14      anton     508: : TO ( c|w|d|r "name" -- ) \ core-ext,local
1.4       anton     509: \ !! state smart
                    510:  0 0 0. 0.0e0 { c: clocal w: wlocal d: dlocal f: flocal }
                    511:  ' dup >definer
                    512:  state @ 
                    513:  if
                    514:    case
                    515:      [ ' locals-wordlist >definer ] literal \ value
                    516:      OF >body POSTPONE Aliteral POSTPONE ! ENDOF
                    517:      [ ' clocal >definer ] literal
                    518:      OF POSTPONE laddr# >body @ lp-offset, POSTPONE c! ENDOF
                    519:      [ ' wlocal >definer ] literal
                    520:      OF POSTPONE laddr# >body @ lp-offset, POSTPONE ! ENDOF
                    521:      [ ' dlocal >definer ] literal
                    522:      OF POSTPONE laddr# >body @ lp-offset, POSTPONE d! ENDOF
                    523:      [ ' flocal >definer ] literal
                    524:      OF POSTPONE laddr# >body @ lp-offset, POSTPONE f! ENDOF
1.11      anton     525:      -&32 throw
1.4       anton     526:    endcase
                    527:  else
                    528:    [ ' locals-wordlist >definer ] literal =
                    529:    if
                    530:      >body !
                    531:    else
1.11      anton     532:      -&32 throw
1.4       anton     533:    endif
                    534:  endif ; immediate
1.1       anton     535: 
1.6       pazsan    536: : locals|
1.14      anton     537:     \ don't use 'locals|'! use '{'! A portable and free '{'
                    538:     \ implementation is anslocals.fs
1.8       anton     539:     BEGIN
                    540:        name 2dup s" |" compare 0<>
                    541:     WHILE
                    542:        (local)
                    543:     REPEAT
1.14      anton     544:     drop 0 (local) ; immediate restrict

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