--- gforth/Attic/gforth.ds 1995/04/29 14:51:16 1.15 +++ gforth/Attic/gforth.ds 1995/11/30 18:04:27 1.26 @@ -2,14 +2,14 @@ @comment The source is gforth.ds, from which gforth.texi is generated @comment %**start of header (This is for running Texinfo on a region.) @setfilename gforth.info -@settitle GNU Forth Manual +@settitle Gforth Manual @comment @setchapternewpage odd @comment %**end of header (This is for running Texinfo on a region.) @ifinfo -This file documents GNU Forth 0.0 +This file documents Gforth 0.1 -Copyright @copyright{} 1994 GNU Forth Development Group +Copyright @copyright{} 1995 Free Software Foundation, Inc. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice @@ -36,18 +36,22 @@ Copyright @copyright{} 1994 GNU Forth De of in the original English. @end ifinfo +@finalout @titlepage @sp 10 -@center @titlefont{GNU Forth Manual} +@center @titlefont{Gforth Manual} @sp 2 -@center for version 0.0 +@center for version 0.1 @sp 2 @center Anton Ertl +@center Bernd Paysan +@sp 3 +@center This manual is under construction @comment The following two commands start the copyright page. @page @vskip 0pt plus 1filll -Copyright @copyright{} 1994 GNU Forth Development Group +Copyright @copyright{} 1995 Free Software Foundation, Inc. @comment !! Published by ... or You can get a copy of this manual ... @@ -72,47 +76,438 @@ Copyright @copyright{} 1994 GNU Forth De @node Top, License, (dir), (dir) @ifinfo -GNU Forth is a free implementation of ANS Forth available on many -personal machines. This manual corresponds to version 0.0. +Gforth is a free implementation of ANS Forth available on many +personal machines. This manual corresponds to version 0.1. @end ifinfo @menu * License:: -* Goals:: About the GNU Forth Project +* Goals:: About the Gforth Project * Other Books:: Things you might want to read -* Invocation:: Starting GNU Forth -* Words:: Forth words available in GNU Forth +* Invocation:: Starting Gforth +* Words:: Forth words available in Gforth * ANS conformance:: Implementation-defined options etc. -* Model:: The abstract machine of GNU Forth -* Emacs and GForth:: The GForth Mode +* Model:: The abstract machine of Gforth +* Emacs and Gforth:: The Gforth Mode * Internals:: Implementation details * Bugs:: How to report them -* Pedigree:: Ancestors of GNU Forth +* Pedigree:: Ancestors of Gforth * Word Index:: An item for each Forth word * Node Index:: An item for each node @end menu @node License, Goals, Top, Top -@unnumbered License -!! Insert GPL here +@unnumbered GNU GENERAL PUBLIC LICENSE +@center Version 2, June 1991 + +@display +Copyright @copyright{} 1989, 1991 Free Software Foundation, Inc. +675 Mass Ave, Cambridge, MA 02139, USA + +Everyone is permitted to copy and distribute verbatim copies +of this license document, but changing it is not allowed. +@end display + +@unnumberedsec Preamble + + The licenses for most software are designed to take away your +freedom to share and change it. By contrast, the GNU General Public +License is intended to guarantee your freedom to share and change free +software---to make sure the software is free for all its users. This +General Public License applies to most of the Free Software +Foundation's software and to any other program whose authors commit to +using it. (Some other Free Software Foundation software is covered by +the GNU Library General Public License instead.) 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It is safest +to attach them to the start of each source file to most effectively +convey the exclusion of warranty; and each file should have at least +the ``copyright'' line and a pointer to where the full notice is found. + +@smallexample +@var{one line to give the program's name and a brief idea of what it does.} +Copyright (C) 19@var{yy} @var{name of author} + +This program is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 2 of the License, or +(at your option) any later version. + +This program is distributed in the hope that it will be useful, +but WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +GNU General Public License for more details. + +You should have received a copy of the GNU General Public License +along with this program; if not, write to the Free Software +Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. +@end smallexample + +Also add information on how to contact you by electronic and paper mail. + +If the program is interactive, make it output a short notice like this +when it starts in an interactive mode: + +@smallexample +Gnomovision version 69, Copyright (C) 19@var{yy} @var{name of author} +Gnomovision comes with ABSOLUTELY NO WARRANTY; for details +type `show w'. +This is free software, and you are welcome to redistribute it +under certain conditions; type `show c' for details. +@end smallexample + +The hypothetical commands @samp{show w} and @samp{show c} should show +the appropriate parts of the General Public License. Of course, the +commands you use may be called something other than @samp{show w} and +@samp{show c}; they could even be mouse-clicks or menu items---whatever +suits your program. + +You should also get your employer (if you work as a programmer) or your +school, if any, to sign a ``copyright disclaimer'' for the program, if +necessary. Here is a sample; alter the names: + +@smallexample +Yoyodyne, Inc., hereby disclaims all copyright interest in the program +`Gnomovision' (which makes passes at compilers) written by James Hacker. + +@var{signature of Ty Coon}, 1 April 1989 +Ty Coon, President of Vice +@end smallexample + +This General Public License does not permit incorporating your program into +proprietary programs. If your program is a subroutine library, you may +consider it more useful to permit linking proprietary applications with the +library. If this is what you want to do, use the GNU Library General +Public License instead of this License. @iftex +@node Preface +@comment node-name, next, previous, up @unnumbered Preface -This manual documents GNU Forth. The reader is expected to know +@cindex Preface +This manual documents Gforth. The reader is expected to know Forth. This manual is primarily a reference manual. @xref{Other Books} for introductory material. @end iftex @node Goals, Other Books, License, Top @comment node-name, next, previous, up -@chapter Goals of GNU Forth +@chapter Goals of Gforth @cindex Goals -The goal of the GNU Forth Project is to develop a standard model for +The goal of the Gforth Project is to develop a standard model for ANSI Forth. This can be split into several subgoals: @itemize @bullet @item -GNU Forth should conform to the ANSI Forth standard. +Gforth should conform to the ANSI Forth standard. @item It should be a model, i.e. it should define all the implementation-dependent things. @@ -121,7 +516,7 @@ It should become standard, i.e. widely a is the most difficult one. @end itemize -To achieve these goals GNU Forth should be +To achieve these goals Gforth should be @itemize @bullet @item Similar to previous models (fig-Forth, F83) @@ -137,32 +532,37 @@ Free. Available on many machines/easy to port. @end itemize -Have we achieved these goals? GNU Forth conforms to the ANS Forth -standard; it may be considered a model, but we have not yet documented +Have we achieved these goals? Gforth conforms to the ANS Forth +standard. It may be considered a model, but we have not yet documented which parts of the model are stable and which parts we are likely to -change; it certainly has not yet become a de facto standard. It has some -similarities and some differences to previous models; It has some -powerful features, but not yet everything that we envisioned; on RISCs -it is as fast as interpreters programmed in assembly, on -register-starved machines it is not so fast, but still faster than any -other C-based interpretive implementation; it is free and available on -many machines. +change. It certainly has not yet become a de facto standard. It has some +similarities and some differences to previous models. It has some +powerful features, but not yet everything that we envisioned. We +certainly have achieved our execution speed goals (@pxref{Performance}). +It is free and available on many machines. @node Other Books, Invocation, Goals, Top @chapter Other books on ANS Forth As the standard is relatively new, there are not many books out yet. It -is not recommended to learn Forth by using GNU Forth and a book that is +is not recommended to learn Forth by using Gforth and a book that is not written for ANS Forth, as you will not know your mistakes from the deviations of the book. There is, of course, the standard, the definite reference if you want to -write ANS Forth programs. It will be available in printed form from -Global Engineering Documents !! somtime in spring or summer 1994. If you -are lucky, you can still get dpANS6 (the draft that was approved as -standard) by aftp from ftp.uu.net:/vendor/minerva/x3j14. +write ANS Forth programs. It is available in printed form from the +National Standards Institute Sales Department (Tel.: USA (212) 642-4900; +Fax.: USA (212) 302-1286) as document @cite{X3.215-1994} for about $200. You +can also get it from Global Engineering Documents (Tel.: USA (800) +854-7179; Fax.: (303) 843-9880) for about $300. + +@cite{dpANS6}, the last draft of the standard, which was then submitted to ANSI +for publication is available electronically and for free in some MS Word +format, and it has been converted to HTML. Some pointers to these +versions can be found through +@*@file{http://www.complang.tuwien.ac.at/projects/forth.html}. -@cite{Forth: The new model} by Jack Woehr (!! Publisher) is an +@cite{Forth: The new model} by Jack Woehr (Prentice-Hall, 1993) is an introductory book based on a draft version of the standard. It does not cover the whole standard. It also contains interesting background information (Jack Woehr was in the ANS Forth Technical Committe). It is @@ -173,7 +573,7 @@ other languages should find it ok. @chapter Invocation You will usually just say @code{gforth}. In many other cases the default -GNU Forth image will be invoked like this: +Gforth image will be invoked like this: @example gforth [files] [-e forth-code] @@ -193,10 +593,12 @@ line. They are: @table @code @item --image-file @var{file} +@item -i @var{file} Loads the Forth image @var{file} instead of the default @file{gforth.fi}. @item --path @var{path} +@item -p @var{path} Uses @var{path} for searching the image file and Forth source code files instead of the default in the environment variable @code{GFORTHPATH} or the path specified at installation time (typically @@ -245,6 +647,12 @@ Forth words, you have to quote them or u after processing the command line (instead of entering interactive mode) append @code{-e bye} to the command line. +If you have several versions of Gforth installed, @code{gforth} will +invoke the version that was installed last. @code{gforth-@var{version}} +invokes a specific version. You may want to use the option +@code{--path}, if your environment contains the variable +@code{GFORTHPATH}. + Not yet implemented: On startup the system first executes the system initialization file (unless the option @code{--no-init-file} is given; note that the system @@ -269,6 +677,7 @@ then in @file{~}, then in the normal pat * Blocks:: * Other I/O:: * Programming Tools:: +* Assembler and Code words:: * Threading Words:: @end menu @@ -285,7 +694,7 @@ that has become a de-facto standard for @table @var @item word -The name of the word. BTW, GNU Forth is case insensitive, so you can +The name of the word. BTW, Gforth is case insensitive, so you can type the words in in lower case (However, @pxref{core-idef}). @item Stack effect @@ -293,13 +702,20 @@ The stack effect is written in the notat @var{after}}, where @var{before} and @var{after} describe the top of stack entries before and after the execution of the word. The rest of the stack is not touched by the word. The top of stack is rightmost, -i.e., a stack sequence is written as it is typed in. Note that GNU Forth +i.e., a stack sequence is written as it is typed in. Note that Gforth uses a separate floating point stack, but a unified stack notation. Also, return stack effects are not shown in @var{stack effect}, but in @var{Description}. The name of a stack item describes the type and/or the function of the item. See below for a discussion of the types. +All words have two stack effects: A compile-time stack effect and a +run-time stack effect. The compile-time stack-effect of most words is +@var{ -- }. If the compile-time stack-effect of a word deviates from +this standard behaviour, or the word does other unusual things at +compile time, both stack effects are shown; otherwise only the run-time +stack effect is shown. + @item pronunciation How the word is pronounced @@ -309,7 +725,11 @@ system need not support all of them. So, uses the more portable it will be in theory. However, we suspect that most ANS Forth systems on personal machines will feature all wordsets. Words that are not defined in the ANS standard have -@code{gforth} as wordset. +@code{gforth} or @code{gforth-internal} as wordset. @code{gforth} +describes words that will work in future releases of Gforth; +@code{gforth-internal} words are more volatile. Environmental query +strings are also displayed like words; you can recognize them by the +@code{environment} in the wordset field. @item Description A description of the behaviour of the word. @@ -409,6 +829,11 @@ doc-sm/rem @node Double precision, Floating Point, Mixed precision, Arithmetic @subsection Double precision + +The outer (aka text) interpreter converts numbers containing a dot into +a double precision number. Note that only numbers with the dot as last +character are standard-conforming. + doc-d+ doc-d- doc-dnegate @@ -419,8 +844,21 @@ doc-dmax @node Floating Point, , Double precision, Arithmetic @subsection Floating Point +The format of floating point numbers recognized by the outer (aka text) +interpreter is: a signed decimal number, possibly containing a decimal +point (@code{.}), followed by @code{E} or @code{e}, optionally followed +by a signed integer (the exponent). E.g., @code{1e} ist the same as +@code{+1.0e+1}. Note that a number without @code{e} +is not interpreted as floating-point number, but as double (if the +number contains a @code{.}) or single precision integer. Also, +conversions between string and floating point numbers always use base +10, irrespective of the value of @code{BASE}. If @code{BASE} contains a +value greater then 14, the @code{E} may be interpreted as digit and the +number will be interpreted as integer, unless it has a signed exponent +(both @code{+} and @code{-} are allowed as signs). + Angles in floating point operations are given in radians (a full circle -has 2 pi radians). Note, that gforth has a separate floating point +has 2 pi radians). Note, that Gforth has a separate floating point stack, but we use the unified notation. Floating point numbers have a number of unpleasant surprises for the @@ -468,7 +906,7 @@ doc-fatanh @node Stack Manipulation, Memory access, Arithmetic, Words @section Stack Manipulation -gforth has a data stack (aka parameter stack) for characters, cells, +Gforth has a data stack (aka parameter stack) for characters, cells, addresses, and double cells, a floating point stack for floating point numbers, a return stack for storing the return addresses of colon definitions and other data, and a locals stack for storing local @@ -594,7 +1032,7 @@ must only occur at specific addresses; e accessed at addresses divisible by 4. Even if a machine allows unaligned accesses, it can usually perform aligned accesses faster. -For the performance-concious: alignment operations are usually only +For the performance-conscious: alignment operations are usually only necessary during the definition of a data structure, not during the (more frequent) accesses to it. @@ -604,7 +1042,7 @@ char-aligned have no use in the standard created. The standard guarantees that addresses returned by @code{CREATE}d words -are cell-aligned; in addition, gforth guarantees that these addresses +are cell-aligned; in addition, Gforth guarantees that these addresses are aligned for all purposes. Note that the standard defines a word @code{char}, which has nothing to @@ -790,13 +1228,27 @@ There are several variations on the coun @code{LEAVE} leaves the innermost counted loop immediately. +If @var{start} is greater than @var{limit}, a @code{?DO} loop is entered +(and @code{LOOP} iterates until they become equal by wrap-around +arithmetic). This behaviour is usually not what you want. Therefore, +Gforth offers @code{+DO} and @code{U+DO} (as replacements for +@code{?DO}), which do not enter the loop if @var{start} is greater than +@var{limit}; @code{+DO} is for signed loop parameters, @code{U+DO} for +unsigned loop parameters. These words can be implemented easily on +standard systems, so using them does not make your programs hard to +port; e.g.: +@example +: +DO ( compile-time: -- do-sys; run-time: n1 n2 -- ) + POSTPONE over POSTPONE min POSTPONE ?DO ; immediate +@end example + @code{LOOP} can be replaced with @code{@var{n} +LOOP}; this updates the index by @var{n} instead of by 1. The loop is terminated when the border between @var{limit-1} and @var{limit} is crossed. E.g.: -@code{4 0 ?DO i . 2 +LOOP} prints @code{0 2} +@code{4 0 +DO i . 2 +LOOP} prints @code{0 2} -@code{4 1 ?DO i . 2 +LOOP} prints @code{1 3} +@code{4 1 +DO i . 2 +LOOP} prints @code{1 3} The behaviour of @code{@var{n} +LOOP} is peculiar when @var{n} is negative: @@ -804,23 +1256,34 @@ The behaviour of @code{@var{n} +LOOP} is @code{ 0 0 ?DO i . -1 +LOOP} prints nothing -Therefore we recommend avoiding using @code{@var{n} +LOOP} with negative -@var{n}. One alternative is @code{@var{n} S+LOOP}, where the negative -case behaves symmetrical to the positive case: +Therefore we recommend avoiding @code{@var{n} +LOOP} with negative +@var{n}. One alternative is @code{@var{u} -LOOP}, which reduces the +index by @var{u} each iteration. The loop is terminated when the border +between @var{limit+1} and @var{limit} is crossed. Gforth also provides +@code{-DO} and @code{U-DO} for down-counting loops. E.g.: + +@code{-2 0 -DO i . 1 -LOOP} prints @code{0 -1} -@code{-2 0 ?DO i . -1 S+LOOP} prints @code{0 -1} +@code{-1 0 -DO i . 1 -LOOP} prints @code{0} -@code{-1 0 ?DO i . -1 S+LOOP} prints @code{0} +@code{ 0 0 -DO i . 1 -LOOP} prints nothing -@code{ 0 0 ?DO i . -1 S+LOOP} prints nothing +Another alternative is @code{@var{n} S+LOOP}, where the negative +case behaves symmetrical to the positive case: -The loop is terminated when the border between @var{limit@minus{}sgn(n)} and -@var{limit} is crossed. However, @code{S+LOOP} is not part of the ANS -Forth standard. +@code{-2 0 -DO i . -1 S+LOOP} prints @code{0 -1} -@code{?DO} can be replaced by @code{DO}. @code{DO} enters the loop even -when the start and the limit value are equal. We do not recommend using -@code{DO}. It will just give you maintenance troubles. +The loop is terminated when the border between @var{limit@minus{}sgn(n)} +and @var{limit} is crossed. Unfortunately, neither @code{-LOOP} nor +@code{S+LOOP} are part of the ANS Forth standard, and they are not easy +to implement using standard words. If you want to write standard +programs, just avoid counting down. + +@code{?DO} can also be replaced by @code{DO}. @code{DO} always enters +the loop, independent of the loop parameters. Do not use @code{DO}, even +if you know that the loop is entered in any case. Such knowledge tends +to become invalid during maintenance of a program, and then the +@code{DO} will make trouble. @code{UNLOOP} is used to prepare for an abnormal loop exit, e.g., via @code{EXIT}. @code{UNLOOP} removes the loop control parameters from the @@ -834,7 +1297,7 @@ FOR NEXT @end example This is the preferred loop of native code compiler writers who are too -lazy to optimize @code{?DO} loops properly. In GNU Forth, this loop +lazy to optimize @code{?DO} loops properly. In Gforth, this loop iterates @var{n+1} times; @code{i} produces values starting with @var{n} and ending with 0. Other Forth systems may behave differently, even if they support @code{FOR} loops. @@ -845,7 +1308,7 @@ they support @code{FOR} loops. ANS Forth permits and supports using control structures in a non-nested way. Information about incomplete control structures is stored on the control-flow stack. This stack may be implemented on the Forth data -stack, and this is what we have done in gforth. +stack, and this is what we have done in Gforth. An @i{orig} entry represents an unresolved forward branch, a @i{dest} entry represents a backward branch target. A few words are the basis for @@ -861,7 +1324,7 @@ doc-again doc-cs-pick doc-cs-roll -On many systems control-flow stack items take one word, in gforth they +On many systems control-flow stack items take one word, in Gforth they currently take three (this may change in the future). Therefore it is a really good idea to manipulate the control flow stack with @code{cs-pick} and @code{cs-roll}, not with data stack manipulation @@ -876,11 +1339,16 @@ doc-repeat Counted loop words constitute a separate group of words: doc-?do +doc-+do +doc-u+do +doc--do +doc-u-do doc-do doc-for doc-loop doc-s+loop doc-+loop +doc--loop doc-next doc-leave doc-?leave @@ -951,7 +1419,8 @@ necessary to define them. @subsection Calls and returns A definition can be called simply be writing the name of the -definition. When the end of the definition is reached, it returns. An earlier return can be forced using +definition. When the end of the definition is reached, it returns. An +earlier return can be forced using doc-exit @@ -976,13 +1445,18 @@ laden with restrictions. Therefore, we p locals wordset, but also our own, more powerful locals wordset (we implemented the ANS Forth locals wordset through our locals wordset). +The ideas in this section have also been published in the paper +@cite{Automatic Scoping of Local Variables} by M. Anton Ertl, presented +at EuroForth '94; it is available at +@*@file{http://www.complang.tuwien.ac.at/papers/ertl94l.ps.gz}. + @menu -* gforth locals:: +* Gforth locals:: * ANS Forth locals:: @end menu -@node gforth locals, ANS Forth locals, Locals, Locals -@subsection gforth locals +@node Gforth locals, ANS Forth locals, Locals, Locals +@subsection Gforth locals Locals can be defined with @@ -1025,7 +1499,7 @@ The name of the local may be preceded by Ar Bi f* Ai Br f* f+ ; @end example -GNU Forth currently supports cells (@code{W:}, @code{W^}), doubles +Gforth currently supports cells (@code{W:}, @code{W^}), doubles (@code{D:}, @code{D^}), floats (@code{F:}, @code{F^}) and characters (@code{C:}, @code{C^}) in two flavours: a value-flavoured local (defined with @code{W:}, @code{D:} etc.) produces its value and can be changed @@ -1045,7 +1519,7 @@ locals are initialized with values from Currently there is no way to define locals with user-defined data structures, but we are working on it. -GNU Forth allows defining locals everywhere in a colon definition. This +Gforth allows defining locals everywhere in a colon definition. This poses the following questions: @menu @@ -1055,7 +1529,7 @@ poses the following questions: * Implementation:: @end menu -@node Where are locals visible by name?, How long do locals live?, gforth locals, gforth locals +@node Where are locals visible by name?, How long do locals live?, Gforth locals, Gforth locals @subsubsection Where are locals visible by name? Basically, the answer is that locals are visible where you would expect @@ -1177,9 +1651,10 @@ If the @code{BEGIN} is not reachable fro @code{AHEAD} or @code{EXIT}), the compiler cannot even make an optimistic guess, as the locals visible after the @code{BEGIN} may be defined later. Therefore, the compiler assumes that no locals are -visible after the @code{BEGIN}. However, the useer can use +visible after the @code{BEGIN}. However, the user can use @code{ASSUME-LIVE} to make the compiler assume that the same locals are -visible at the BEGIN as at the point where the item was created. +visible at the BEGIN as at the point where the top control-flow stack +item was created. doc-assume-live @@ -1213,7 +1688,7 @@ WHILE REPEAT @end example -@node How long do locals live?, Programming Style, Where are locals visible by name?, gforth locals +@node How long do locals live?, Programming Style, Where are locals visible by name?, Gforth locals @subsubsection How long do locals live? The right answer for the lifetime question would be: A local lives at @@ -1227,7 +1702,7 @@ languages (e.g., C): The local lives onl afterwards its address is invalid (and programs that access it afterwards are erroneous). -@node Programming Style, Implementation, How long do locals live?, gforth locals +@node Programming Style, Implementation, How long do locals live?, Gforth locals @subsubsection Programming Style The freedom to define locals anywhere has the potential to change @@ -1241,7 +1716,7 @@ write the items in the order you want. This seems a little far-fetched and eliminating stack manipulations is unlikely to become a conscious programming objective. Still, the number of stack manipulations will be reduced dramatically if local variables -are used liberally (e.g., compare @code{max} in @ref{gforth locals} with +are used liberally (e.g., compare @code{max} in @ref{Gforth locals} with a traditional implementation of @code{max}). This shows one potential benefit of locals: making Forth programs more @@ -1296,10 +1771,10 @@ are initialized with the right value for Here it is clear from the start that @code{s1} has a different value in every loop iteration. -@node Implementation, , Programming Style, gforth locals +@node Implementation, , Programming Style, Gforth locals @subsubsection Implementation -GNU Forth uses an extra locals stack. The most compelling reason for +Gforth uses an extra locals stack. The most compelling reason for this is that the return stack is not float-aligned; using an extra stack also eliminates the problems and restrictions of using the return stack as locals stack. Like the other stacks, the locals stack grows toward @@ -1334,7 +1809,7 @@ area and @code{@}} switches it back and initializing code. @code{W:} etc.@ are normal defining words. This special area is cleared at the start of every colon definition. -A special feature of GNU Forths dictionary is used to implement the +A special feature of Gforth's dictionary is used to implement the definition of locals without type specifiers: every wordlist (aka vocabulary) has its own methods for searching etc. (@pxref{Wordlists}). For the present purpose we defined a wordlist @@ -1424,12 +1899,12 @@ this may lead to increased space needs f usually less than reclaiming this space would cost in code size. -@node ANS Forth locals, , gforth locals, Locals +@node ANS Forth locals, , Gforth locals, Locals @subsection ANS Forth locals The ANS Forth locals wordset does not define a syntax for locals, but words that make it possible to define various syntaxes. One of the -possible syntaxes is a subset of the syntax we used in the gforth locals +possible syntaxes is a subset of the syntax we used in the Gforth locals wordset, i.e.: @example @@ -1445,13 +1920,13 @@ restrictions are: @itemize @bullet @item -Locals can only be cell-sized values (no type specifers are allowed). +Locals can only be cell-sized values (no type specifiers are allowed). @item Locals can be defined only outside control structures. @item Locals can interfere with explicit usage of the return stack. For the exact (and long) rules, see the standard. If you don't use return stack -accessing words in a definition using locals, you will we all right. The +accessing words in a definition using locals, you will be all right. The purpose of this rule is to make locals implementation on the return stack easier. @item @@ -1462,7 +1937,7 @@ Locals defined in this way behave like @ (@xref{Values}). I.e., they are initialized from the stack. Using their name produces their value. Their value can be changed using @code{TO}. -Since this syntax is supported by gforth directly, you need not do +Since this syntax is supported by Gforth directly, you need not do anything to use it. If you want to port a program using this syntax to another ANS Forth system, use @file{anslocal.fs} to implement the syntax on the other system. @@ -1477,7 +1952,7 @@ doc-(local) The ANS Forth locals extension wordset defines a syntax, but it is so awful that we strongly recommend not to use it. We have implemented this -syntax to make porting to gforth easy, but do not document it here. The +syntax to make porting to Gforth easy, but do not document it here. The problem with this syntax is that the locals are defined in an order reversed with respect to the standard stack comment notation, making programs harder to read, and easier to misread and miswrite. The only @@ -1506,7 +1981,7 @@ locals wordset. @node Other I/O, Programming Tools, Blocks, Words @section Other I/O -@node Programming Tools, Threading Words, Other I/O, Words +@node Programming Tools, Assembler and Code words, Other I/O, Words @section Programming Tools @menu @@ -1551,7 +2026,7 @@ doc-printdebugline It is a good idea to make your programs self-checking, in particular, if you use an assumption (e.g., that a certain field of a data structure is -never zero) that may become wrong during maintenance. GForth supports +never zero) that may become wrong during maintenance. Gforth supports assertions for this purpose. They are used like this: @example @@ -1574,7 +2049,7 @@ debugging, we want more checking, in pro for speed. Therefore, assertions can be turned off, i.e., the assertion becomes a comment. Depending on the importance of an assertion and the time it takes to check it, you may want to turn off some assertions and -keep others turned on. GForth provides several levels of assertions for +keep others turned on. Gforth provides several levels of assertions for this purpose: doc-assert0( @@ -1605,11 +2080,79 @@ If there is interest, we will introduce intend to @code{catch} a specific condition, using @code{throw} is probably more appropriate than an assertion). -@node Threading Words, , Programming Tools, Words +@node Assembler and Code words, Threading Words, Programming Tools, Words +@section Assembler and Code words + +Gforth provides some words for defining primitives (words written in +machine code), and for defining the the machine-code equivalent of +@code{DOES>}-based defining words. However, the machine-independent +nature of Gforth poses a few problems: First of all. Gforth runs on +several architectures, so it can provide no standard assembler. What's +worse is that the register allocation not only depends on the processor, +but also on the @code{gcc} version and options used. + +The words that Gforth offers encapsulate some system dependences (e.g., the +header structure), so a system-independent assembler may be used in +Gforth. If you do not have an assembler, you can compile machine code +directly with @code{,} and @code{c,}. + +doc-assembler +doc-code +doc-end-code +doc-;code +doc-flush-icache + +If @code{flush-icache} does not work correctly, @code{code} words +etc. will not work (reliably), either. + +These words are rarely used. Therefore they reside in @code{code.fs}, +which is usually not loaded (except @code{flush-icache}, which is always +present). You can load them with @code{require code.fs}. + +In the assembly code you will want to refer to the inner interpreter's +registers (e.g., the data stack pointer) and you may want to use other +registers for temporary storage. Unfortunately, the register allocation +is installation-dependent. + +The easiest solution is to use explicit register declarations +(@pxref{Explicit Reg Vars, , Variables in Specified Registers, gcc.info, +GNU C Manual}) for all of the inner interpreter's registers: You have to +compile Gforth with @code{-DFORCE_REG} (configure option +@code{--enable-force-reg}) and the appropriate declarations must be +present in the @code{machine.h} file (see @code{mips.h} for an example; +you can find a full list of all declarable register symbols with +@code{grep register engine.c}). If you give explicit registers to all +variables that are declared at the beginning of @code{engine()}, you +should be able to use the other caller-saved registers for temporary +storage. Alternatively, you can use the @code{gcc} option +@code{-ffixed-REG} (@pxref{Code Gen Options, , Options for Code +Generation Conventions, gcc.info, GNU C Manual}) to reserve a register +(however, this restriction on register allocation may slow Gforth +significantly). + +If this solution is not viable (e.g., because @code{gcc} does not allow +you to explicitly declare all the registers you need), you have to find +out by looking at the code where the inner interpreter's registers +reside and which registers can be used for temporary storage. You can +get an assembly listing of the engine's code with @code{make engine.s}. + +In any case, it is good practice to abstract your assembly code from the +actual register allocation. E.g., if the data stack pointer resides in +register @code{$17}, create an alias for this register called @code{sp}, +and use that in your assembly code. + +Another option for implementing normal and defining words efficiently +is: adding the wanted functionality to the source of Gforth. For normal +words you just have to edit @file{primitives}, defining words (for fast +defined words) may require changes in @file{engine.c}, +@file{kernal.fs}, @file{prims2x.fs}, and possibly @file{cross.fs}. + + +@node Threading Words, , Assembler and Code words, Words @section Threading Words These words provide access to code addresses and other threading stuff -in gforth (and, possibly, other interpretive Forths). It more or less +in Gforth (and, possibly, other interpretive Forths). It more or less abstracts away the differences between direct and indirect threading (and, for direct threading, the machine dependences). However, at present this wordset is still inclomplete. It is also pretty low-level; @@ -1623,12 +2166,25 @@ doc-does-code! doc-does-handler! doc-/does-handler +The code addresses produced by various defining words are produced by +the following words: +doc-docol: +doc-docon: +doc-dovar: +doc-douser: +doc-dodefer: +doc-dofield: + +Currently there is no installation-independent way for recogizing words +defined by a @code{CREATE}...@code{DOES>} word; however, once you know +that a word is defined by a @code{CREATE}...@code{DOES>} word, you can +use @code{>DOES-CODE}. @node ANS conformance, Model, Words, Top @chapter ANS conformance -To the best of our knowledge, gforth is an +To the best of our knowledge, Gforth is an ANS Forth System @itemize @@ -1650,7 +2206,7 @@ ANS Forth System @item providing the Memory-Allocation word set @item providing the Memory-Allocation Extensions word set (that one's easy) @item providing the Programming-Tools word set -@item providing @code{AHEAD}, @code{BYE}, @code{CS-PICK}, @code{CS-ROLL}, @code{STATE}, @code{[ELSE]}, @code{[IF]}, @code{[THEN]} from the Programming-Tools Extensions word set +@item providing @code{;code}, @code{AHEAD}, @code{ASSEMBLER}, @code{BYE}, @code{CODE}, @code{CS-PICK}, @code{CS-ROLL}, @code{STATE}, @code{[ELSE]}, @code{[IF]}, @code{[THEN]} from the Programming-Tools Extensions word set @item providing the Search-Order word set @item providing the Search-Order Extensions word set @item providing the String word set @@ -1663,7 +2219,7 @@ requirements. In many cases it gives a w information instead of providing the information directly, in particular, if the information depends on the processor, the operating system or the installation options chosen, or if they are likely to -change during the maintenance of gforth. +change during the maintenance of Gforth. @comment The framework for the rest has been taken from pfe. @@ -1702,7 +2258,7 @@ change during the maintenance of gforth. @table @i @item (Cell) aligned addresses: -processor-dependent. Gforths alignment words perform natural alignment +processor-dependent. Gforth's alignment words perform natural alignment (e.g., an address aligned for a datum of size 8 is divisible by 8). Unaligned accesses usually result in a @code{-23 THROW}. @@ -1727,10 +2283,10 @@ installation-dependent. Currently a char (Comments on that requested). @item character-set extensions and matching of names: -Any character except 0 can be used in a name. Matching is -case-insensitive. The matching is performed using the C function -@code{strncasecmp}, whose function is probably influenced by the -locale. E.g., the @code{C} locale does not know about accents and +Any character except the ASCII NUL charcter can be used in a +name. Matching is case-insensitive. The matching is performed using the +C function @code{strncasecmp}, whose function is probably influenced by +the locale. E.g., the @code{C} locale does not know about accents and umlauts, so they are matched case-sensitively in that locale. For portability reasons it is best to write programs such that they work in the @code{C} locale. Then one can use libraries written by a Polish @@ -1790,19 +2346,19 @@ Given by the constant @code{/line}. Curr 31 @item method of selecting the user input device: -The user input device is the standard input. There is current no way to -change it from within gforth. However, the input can typically be -redirected in the command line that starts gforth. +The user input device is the standard input. There is currently no way to +change it from within Gforth. However, the input can typically be +redirected in the command line that starts Gforth. @item method of selecting the user output device: The user output device is the standard output. It cannot be redirected -from within gforth, but typically from the command line that starts -gforth. Gforth uses buffered output, so output on a terminal does not +from within Gforth, but typically from the command line that starts +Gforth. Gforth uses buffered output, so output on a terminal does not become visible before the next newline or buffer overflow. Output on non-terminals is invisible until the buffer overflows. @item methods of dictionary compilation: -Waht are we expected to document here? +What are we expected to document here? @item number of bits in one address unit: @code{s" address-units-bits" environment? drop .}. 8 in all current @@ -1838,7 +2394,7 @@ string. Varies. You can determine the size at a specific time using @code{lp@ tib - .}. It is shared with the locals stack and TIBs of files that include the current file. You can change the amount of space for TIBs -and locals stack at gforth startup with the command line option +and locals stack at Gforth startup with the command line option @code{-l}. @item size of the pictured numeric output buffer: @@ -1861,7 +2417,7 @@ characters is determined by the locale y @item division rounding: installation dependent. @code{s" floored" environment? drop .}. We leave -the choice to gcc (what to use for @code{/}) and to you (whether to use +the choice to @code{gcc} (what to use for @code{/}) and to you (whether to use @code{fm/mod}, @code{sm/rem} or simply @code{/}). @item values of @code{STATE} when true: @@ -1972,9 +2528,9 @@ The next invocation of a parsing word re Compiles a recursive call to the defining word not to the defined word. @item argument input source different than current input source for @code{RESTORE-INPUT}: -!!???If the argument input source is a valid input source then it gets -restored. Otherwise causes @code{-12 THROW} which unless caught issues -the message "argument type mismatch" and aborts. +If the argument input source is a valid input source then it gets +restored. Otherwise the result is undefined. +@comment causes @code{-12 THROW}, which, unless caught, issues the message "argument type mismatch" and aborts. !! not all of the state is restored (e.g., sourcefilename). @item data space containing definitions gets de-allocated: Deallocation with @code{allot} is not checked. This typically resuls in @@ -2046,14 +2602,17 @@ Not checked. As usual, you can expect me None. @item operator's terminal facilities available: -!!?? +After processing the command line, Gforth goes into interactive mode, +and you can give commands to Gforth interactively. The actual facilities +available depend on how you invoke Gforth. @item program data space available: @code{sp@ here - .} gives the space remaining for dictionary and data stack together. @item return stack space available: -!!?? +By default 16 KBytes. The default can be overridden with the @code{-r} +switch (@pxref{Invocation}) when Gforth starts up. @item stack space available: @code{sp@ here - .} gives the space remaining for dictionary and data @@ -2216,7 +2775,7 @@ another question. @item repeatability to be expected from the execution of @code{MS}: System dependent. On Unix, a lot depends on load. If the system is -lightly loaded, and the delay is short enough that gforth does not get +lightly loaded, and the delay is short enough that Gforth does not get swapped out, the performance should be acceptable. Under MS-DOS and other single-tasking systems, it should be good. @@ -2374,7 +2933,10 @@ System dependent; @code{REPRESENT} is im function @code{ecvt()} and inherits its behaviour in this respect. @item rounding or truncation of floating-point numbers: -What's the question?!! +System dependent; the rounding behaviour is inherited from the hosting C +compiler. IEEE-FP-based (i.e., most) systems by default round to +nearest, and break ties by rounding to even (i.e., such that the last +bit of the mantissa is 0). @item size of floating-point stack: @code{s" FLOATING-STACK" environment? drop .}. Can be changed at startup @@ -2647,13 +3209,13 @@ when @code{REVEAL} is executed (by @code @end table -@node Model, Emacs and GForth, ANS conformance, Top +@node Model, Emacs and Gforth, ANS conformance, Top @chapter Model -@node Emacs and GForth, Internals, Model, Top -@chapter Emacs and GForth +@node Emacs and Gforth, Internals, Model, Top +@chapter Emacs and Gforth -GForth comes with @file{gforth.el}, an improved version of +Gforth comes with @file{gforth.el}, an improved version of @file{forth.el} by Goran Rydqvist (icluded in the TILE package). The improvements are a better (but still not perfect) handling of indentation. I have also added comment paragraph filling (@kbd{M-q}), @@ -2663,7 +3225,7 @@ stuff I do not use alone, even though so TILE. To get a description of these features, enter Forth mode and type @kbd{C-h m}. -In addition, GForth supports Emacs quite well: The source code locations +In addition, Gforth supports Emacs quite well: The source code locations given in error messages, debugging output (from @code{~~}) and failed assertion messages are in the right format for Emacs' compilation mode (@pxref{Compilation, , Running Compilations under Emacs, emacs, Emacs @@ -2675,7 +3237,7 @@ Also, if you @code{include} @file{etags. (@pxref{Tags, , Tags Tables, emacs, Emacs Manual}) will be produced that contains the definitions of all words defined afterwards. You can then find the source for a word using @kbd{M-.}. Note that emacs can use -several tags files at the same time (e.g., one for the gforth sources +several tags files at the same time (e.g., one for the Gforth sources and one for your program). To get all these benefits, add the following lines to your @file{.emacs} @@ -2686,17 +3248,24 @@ file: (setq auto-mode-alist (cons '("\\.fs\\'" . forth-mode) auto-mode-alist)) @end example -@node Internals, Bugs, Emacs and GForth, Top +@node Internals, Bugs, Emacs and Gforth, Top @chapter Internals -Reading this section is not necessary for programming with gforth. It -should be helpful for finding your way in the gforth sources. +Reading this section is not necessary for programming with Gforth. It +should be helpful for finding your way in the Gforth sources. + +The ideas in this section have also been published in the papers +@cite{ANS fig/GNU/??? Forth} (in German) by Bernd Paysan, presented at +the Forth-Tagung '93 and @cite{A Portable Forth Engine} by M. Anton +Ertl, presented at EuroForth '93; the latter is available at +@*@file{http://www.complang.tuwien.ac.at/papers/ertl93.ps.Z}. @menu * Portability:: * Threading:: * Primitives:: * System Architecture:: +* Performance:: @end menu @node Portability, Threading, Internals, Internals @@ -2728,9 +3297,7 @@ Double-Word Integers, gcc.info, GNU C Ma double numbers. GNU C is available for free on all important (and many unimportant) UNIX machines, VMS, 80386s running MS-DOS, the Amiga, and the Atari ST, so a Forth written in GNU C can run on all these -machines@footnote{Due to Apple's look-and-feel lawsuit it is not -available on the Mac (@pxref{Boycott, , Protect Your Freedom---Fight -``Look And Feel'', gcc.info, GNU C Manual}).}. +machines. Writing in a portable language has the reputation of producing code that is slower than assembly. For our Forth engine we repeatedly looked at @@ -3021,7 +3588,7 @@ To see what assembly code is produced fo with your compiler and your flag settings, type @code{make engine.s} and look at the resulting file @file{engine.s}. -@node System Architecture, , Primitives, Internals +@node System Architecture, Performance, Primitives, Internals @section System Architecture Our Forth system consists not only of primitives, but also of @@ -3044,7 +3611,7 @@ possible, because we do not want to dist same image file, and to make it easy for the users to use their image files on many machines. We currently need to create a different image file for machines with different cell sizes and different byte order -(little- or big-endian)@footnote{We consider adding information to the +(little- or big-endian)@footnote{We are considering adding information to the image file that enables the loader to change the byte order.}. Forth code that is going to end up in a portable image file has to @@ -3064,18 +3631,162 @@ at run-time. The loader also has to repl primitive calls with the appropriate code-field addresses (or code addresses in the case of direct threading). +@node Performance, , System Architecture, Internals +@section Performance + +On RISCs the Gforth engine is very close to optimal; i.e., it is usually +impossible to write a significantly faster engine. + +On register-starved machines like the 386 architecture processors +improvements are possible, because @code{gcc} does not utilize the +registers as well as a human, even with explicit register declarations; +e.g., Bernd Beuster wrote a Forth system fragment in assembly language +and hand-tuned it for the 486; this system is 1.19 times faster on the +Sieve benchmark on a 486DX2/66 than Gforth compiled with +@code{gcc-2.6.3} with @code{-DFORCE_REG}. + +However, this potential advantage of assembly language implementations +is not necessarily realized in complete Forth systems: We compared +Gforth (direct threaded, compiled with @code{gcc-2.6.3} and +@code{-DFORCE_REG}) with Win32Forth 1.2093, LMI's NT Forth (Beta, May +1994) and Eforth (with and without peephole (aka pinhole) optimization +of the threaded code); all these systems were written in assembly +language. We also compared Gforth with two systems written in C: +PFE-0.9.11 (compiled with @code{gcc-2.6.3} with the default +configuration for Linux: @code{-O2 -fomit-frame-pointer -DUSE_REGS}) and +ThisForth Beta (compiled with gcc-2.6.3 -O3 -fomit-frame-pointer; +ThisForth employs peephole optimization of the threaded code). We +benchmarked Gforth, PFE and ThisForth on a 486DX2/66 under +Linux. Kenneth O'Heskin kindly provided the results for Win32Forth and +NT Forth on a 486DX2/66 with similar memory performance under Windows +NT. Marcel Hendrix ported Eforth to Linux, then extended it to run the +benchmarks, added the peephole optimizer, ran the benchmarks and +reported the results. + +We used four small benchmarks: the ubiquitous Sieve; bubble-sorting and +matrix multiplication come from the Stanford integer benchmarks and have +been translated into Forth by Martin Fraeman; we used the versions +included in the TILE Forth package; and a recursive Fibonacci number +computation for benchmarking calling performance. The following table shows +the time taken for the benchmarks scaled by the time taken by Gforth (in +other words, it shows the speedup factor that Gforth achieved over the +other systems). + +@example +relative Win32- NT eforth This- +time Gforth Forth Forth eforth +opt PFE Forth +sieve 1.00 1.39 1.14 1.39 0.85 1.78 3.18 +bubble 1.00 1.33 1.43 1.51 0.89 1.70 +matmul 1.00 1.43 1.31 1.42 1.12 2.28 +fib 1.00 1.55 1.36 1.24 1.15 1.97 3.04 +@end example + +You may find the good performance of Gforth compared with the systems +written in assembly language quite surprising. One important reason for +the disappointing performance of these systems is probably that they are +not written optimally for the 486 (e.g., they use the @code{lods} +instruction). In addition, Win32Forth uses a comfortable, but costly +method for relocating the Forth image: like @code{cforth}, it computes +the actual addresses at run time, resulting in two address computations +per NEXT (@pxref{System Architecture}). + +Only Eforth with the peephole optimizer performs comparable to +Gforth. The speedups achieved with peephole optimization of threaded +code are quite remarkable. Adding a peephole optimizer to Gforth should +cause similar speedups. + +The speedup of Gforth over PFE and ThisForth can be easily explained +with the self-imposed restriction to standard C (although the measured +implementation of PFE uses a GNU C extension: global register +variables), which makes efficient threading impossible. Moreover, +current C compilers have a hard time optimizing other aspects of the +ThisForth source. + +Note that the performance of Gforth on 386 architecture processors +varies widely with the version of @code{gcc} used. E.g., @code{gcc-2.5.8} +failed to allocate any of the virtual machine registers into real +machine registers by itself and would not work correctly with explicit +register declarations, giving a 1.3 times slower engine (on a 486DX2/66 +running the Sieve) than the one measured above. + +In @cite{Translating Forth to Efficient C} by M. Anton Ertl and Martin +Maierhofer (presented at EuroForth '95), an indirect threaded version of +Gforth is compared with Win32Forth, NT Forth, PFE, and ThisForth; that +version of Gforth is 2\%@minus{}8\% slower on a 486 than the version +used here. The paper available at +@*@file{http://www.complang.tuwien.ac.at/papers/ertl&maierhofer95.ps.gz}; +it also contains numbers for some native code systems. You can find +numbers for Gforth on various machines in @file{Benchres}. + @node Bugs, Pedigree, Internals, Top @chapter Bugs +Known bugs are described in the file BUGS in the Gforth distribution. + +If you find a bug, please send a bug report to +@code{gforth-bugs@@mips.complang.tuwien.ac.at}. A bug report should +describe the Gforth version used (it is announced at the start of an +interactive Gforth session), the machine and operating system (on Unix +systems you can use @code{uname -a} to produce this information), the +installation options (send the @code{config.status} file), and a +complete list of changes you (or your installer) have made to the Gforth +sources (if any); it should contain a program (or a sequence of keyboard +commands) that reproduces the bug and a description of what you think +constitutes the buggy behaviour. + +For a thorough guide on reporting bugs read @ref{Bug Reporting, , How +to Report Bugs, gcc.info, GNU C Manual}. + + @node Pedigree, Word Index, Bugs, Top @chapter Pedigree +Gforth descends from BigForth (1993) and fig-Forth. Gforth and PFE (by +Dirk Zoller) will cross-fertilize each other. Of course, a significant +part of the design of Gforth was prescribed by ANS Forth. + +Bernd Paysan wrote BigForth, a descendent from TurboForth, an unreleased +32 bit native code version of VolksForth for the Atari ST, written +mostly by Dietrich Weineck. + +VolksForth descends from F83. It was written by Klaus Schleisiek, Bernd +Pennemann, Georg Rehfeld and Dietrich Weineck for the C64 (called +UltraForth there) in the mid-80s and ported to the Atari ST in 1986. + +Hennry Laxen and Mike Perry wrote F83 as a model implementation of the +Forth-83 standard. !! Pedigree? When? + +A team led by Bill Ragsdale implemented fig-Forth on many processors in +1979. Robert Selzer and Bill Ragsdale developed the original +implementation of fig-Forth for the 6502 based on microForth. + +The principal architect of microForth was Dean Sanderson. microForth was +FORTH, Inc.'s first off-the-shelf product. It was developped in 1976 for +the 1802, and subsequently implemented on the 8080, the 6800 and the +Z80. + +All earlier Forth systems were custom-made, usually by Charles Moore, +who discovered (as he puts it) Forth in the late 60s. + +A part of the information in this section comes from @cite{The Evolution +of Forth} by Elizabeth D. Rather, Donald R. Colburn and Charles +H. Moore, presented at the HOPL-II conference and preprinted in SIGPLAN +Notices 28(3), 1993. You can find more historical and genealogical +information about Forth there. + @node Word Index, Node Index, Pedigree, Top @chapter Word Index +This index is as incomplete as the manual. Each word is listed with +stack effect and wordset. + +@printindex fn + @node Node Index, , Word Index, Top @chapter Node Index +This index is even less complete than the manual. + @contents @bye