File:  [gforth] / gforth / kernel / vars.fs
Revision 1.19: download - view: text, annotated - select for diffs
Mon Nov 8 22:01:12 1999 UTC (21 years, 8 months ago) by crook
Branches: MAIN
CVS tags: HEAD
Various minor documentation changes to match the latest gforth.ds

    1: \ VARS.FS      Kernal variables
    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: hex \ everything now hex!                               11may93jaw
   22: 
   23: \ important constants                                  17dec92py
   24: 
   25: \ dpANS6 (sect 3.1.3.1) says 
   26: \ "a true flag ... [is] a single-cell value with all bits set"
   27: \ better definition: 0 0= constant true ( no dependence on 2's compl)
   28:  -1 Constant true ( -- f ) \ core-ext
   29: \G @code{Constant} -- @i{f} is a cell with all bits set.
   30: \ see starts looking for primitives after this word!
   31: 
   32:   0 Constant false ( -- f ) \ core-ext
   33: \G @code{Constant} -- @i{f} is a cell with all bits clear.
   34: 
   35: [IFUNDEF] cell 
   36: 1 cells Constant cell ( -- u ) \ gforth
   37: \G @code{Constant} -- the number of address units corresponding to 1 cell.
   38: [THEN]
   39: 
   40: 1 floats Constant float ( -- u ) \ gforth
   41: \G @code{Constant} -- the number of address units corresponding to a floating-point number.
   42: 
   43: 20 Constant bl ( -- c-char ) \ core
   44: \G @i{c-char} is the character value for a space.
   45: \ used by docon:, must be constant
   46: 
   47: FF Constant /line
   48: 
   49: 40 Constant c/l
   50: 10 Constant l/s
   51: 400 Constant chars/block
   52: 
   53: 20 8 2* cells + 2 + cell+ constant word-pno-size ( -- u )
   54: create holdbuf word-pno-size chars allot
   55: holdbuf word-pno-size chars + aconstant holdbuf-end
   56: avariable holdptr holdbuf-end holdptr a!
   57: avariable holdend holdbuf-end holdend a!
   58: 
   59: 84 constant pad-minsize ( -- u )
   60: 
   61: 
   62: \ that's enough so long
   63: 
   64: \ User variables                                       13feb93py
   65: 
   66: \ initialized by COLD
   67: 
   68: Create main-task  has? OS [IF] 100 [ELSE] 40 [THEN] cells allot
   69: 
   70: \ set user-pointer from cross-compiler right
   71: main-task 
   72: UNLOCK tup ! LOCK
   73: 
   74: Variable udp ( -- a-addr ) \ gforth
   75: \ user area size? -anton
   76: 
   77: AUser next-task        main-task next-task !
   78: AUser prev-task        main-task prev-task !
   79: AUser save-task        0 save-task !
   80: AUser sp0 ( -- a-addr ) \ gforth
   81: \G @code{User} variable -- initial value of the data stack pointer.
   82: \ sp0 is used by douser:, must be user
   83:     ' sp0 Alias s0 ( -- a-addr ) \ gforth
   84: \G OBSOLETE alias of @code{sp0}
   85: 
   86: AUser rp0 ( -- a-addr ) \ gforth
   87: \G @code{User} variable -- initial value of the return stack pointer.
   88:     ' rp0 Alias r0 ( -- a-addr ) \ gforth
   89: \G OBSOLETE alias of @code{rp0}
   90: 
   91: AUser fp0 ( -- a-addr ) \ gforth
   92: \G @code{User} variable -- initial value of the floating-point stack pointer.
   93: \ no f0, because this leads to unexpected results when using hex
   94: 
   95: AUser lp0 ( -- a-addr ) \ gforth
   96: \G @code{User} variable -- initial value of the locals stack pointer.
   97:     ' lp0 Alias l0 ( -- a-addr ) \ gforth
   98: \G OBSOLETE alias of @code{lp0}
   99: 
  100: AUser handler	\ pointer to last throw frame
  101: has? backtrace [IF]
  102: User backtrace-empty \ true if the next THROW should store a backtrace
  103: AUser backtrace-rp0 \ rp at last call of interpret
  104: [THEN]
  105: \ AUser output
  106: \ AUser input
  107: 
  108: AUser errorhandler
  109: 
  110: AUser "error            0 "error !
  111: 
  112: [IFUNDEF] #tib		\ in ec-Version we may define this ourself
  113:  User tibstack		\ saves >tib in execute
  114:  User >tib		\ pointer to terminal input buffer
  115:  User #tib ( -- a-addr ) \ core-ext
  116:  \G @code{User} variable -- @i{a-addr} is the address of a cell containing
  117:  \G the number of characters in the terminal input buffer.
  118:  \G OBSOLESCENT: @code{source} superceeds the function of this word.
  119: 
  120:  User >in ( -- a-addr ) \ core
  121:  \G @code{User} variable -- @i{a-addr} is the address of a cell containing the
  122:  \G char offset from the start of the input buffer to the start of the
  123:  \G parse area.
  124:                         0 >in ! \ char number currently processed in tib
  125: [THEN]
  126: has? file [IF]
  127:  User blk ( -- a-addr ) \ block
  128:  \G @code{User} variable -- @i{a-addr} is the address of a cell containing zero
  129:  \G (in which case the input source is not a block and can be identified
  130:  \G by @code{source-id}) or the number of the block currently being
  131:  \G interpreted. A Standard program should not alter @code{blk} directly.
  132: 			0 blk !
  133: 
  134:  User loadfile          0 loadfile !
  135: 
  136:  User loadfilename#	0 loadfilename# !
  137: 
  138:  User loadline          \ number of the currently interpreted
  139:                         \ (in TIB) line if the interpretation
  140:                         \ is in a textfile
  141:                         \ the first line is 1
  142: 
  143: 2User linestart         \ starting file postition of
  144:                         \ the current interpreted line (in TIB)
  145: [THEN]
  146: 
  147:  User base ( -- a-addr ) \ core
  148:  \G @code{User} variable -- @i{a-addr} is the address of a cell that stores the
  149:  \G number base used by default for number conversion during input and output.
  150:                         A base !
  151:  User dpl ( -- a-addr ) \ gforth
  152:  \G @code{User} variable -- @i{a-addr} is the address of a cell that stores the 		
  153:  \G position of the decimal point in the most recent numeric conversion.
  154:  \G Initialised to -1. After the conversion of a number containing no
  155:  \G decimal point, @code{@ dpl} is -1. After the conversion of @code{2.} it holds
  156:  \G 0. After the conversion of 234123.9 it contains 1, and so forth.
  157:  -1 dpl !
  158: 
  159:  User state ( -- a-addr ) \ core,tools-ext
  160:  \G @code{User} variable -- @i{a-addr} is the address of a cell containing the
  161:  \G compilation state flag. 0 => interpreting, -1 => compiling.  A
  162:  \G program shall not directly alter the value of @code{state}. The
  163:  \G following Standard words alter the value in @code{state}: @code{:}
  164:  \G (colon) @code{;} (semicolon) @code{abort} @code{quit}
  165:  \G @code{:noname} @code{[} (left-bracket) @code{]} (right-bracket)
  166:  \G @code{;code}. Don't use @code{state}! @xref{Interpretation and
  167:  \G Compilation Semantics} for an alternative. 
  168:  \  Recommended reading: @cite{@code{State}-smartness--Why it is evil
  169:  \  and how to exorcise it},
  170:  \  @url{http://www.complang.tuwien.ac.at/papers/ertl98.ps.gz}; short
  171:  \  version: Don't use @code{state}! 
  172:  0 state !
  173: 
  174: AUser normal-dp		\ the usual dictionary pointer
  175: AUser dpp		normal-dp dpp !
  176: 			\ the pointer to the current dictionary pointer
  177:                         \ ist reset to normal-dp on (doerror)
  178:                         \  (i.e. any throw caught by quit)
  179: AUser LastCFA
  180: AUser Last
  181: 
  182: has? glocals [IF]
  183: User locals-size \ this is the current size of the locals stack
  184: 		 \ frame of the current word
  185: [THEN]
  186: 

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