--- gforth/Attic/gforth.ds 1995/04/29 14:51:16 1.15 +++ gforth/Attic/gforth.ds 1995/10/07 17:38:14 1.18 @@ -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{} 1994 Gforth Development Group Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice @@ -38,16 +38,18 @@ Copyright @copyright{} 1994 GNU Forth De @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 +@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{} 1994 Gforth Development Group @comment !! Published by ... or You can get a copy of this manual ... @@ -72,22 +74,22 @@ Copyright @copyright{} 1994 GNU Forth De @node Top, License, (dir), (dir) @ifinfo -GNU Forth is a free implementation of ANS Forth available on many +Gforth is a free implementation of ANS Forth available on many personal machines. This manual corresponds to version 0.0. @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 @@ -98,21 +100,21 @@ personal machines. This manual correspon @iftex @unnumbered Preface -This manual documents GNU Forth. The reader is expected to know +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 +123,7 @@ 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) @@ -137,22 +139,20 @@ 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. @@ -173,7 +173,7 @@ 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] @@ -269,6 +269,7 @@ then in @file{~}, then in the normal pat * Blocks:: * Other I/O:: * Programming Tools:: +* Assembler and Code words:: * Threading Words:: @end menu @@ -285,7 +286,7 @@ 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 @@ -293,7 +294,7 @@ 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 @@ -409,6 +410,11 @@ 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 +425,21 @@ 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 +487,7 @@ 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 +613,7 @@ 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 +623,7 @@ 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 +809,27 @@ 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 +837,34 @@ 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 S+LOOP} prints @code{0 -1} +@code{-2 0 -DO i . 1 -LOOP} prints @code{0 -1} -@code{-1 0 ?DO i . -1 S+LOOP} prints @code{0} +@code{-1 0 -DO i . 1 -LOOP} prints @code{0} -@code{ 0 0 ?DO i . -1 S+LOOP} prints nothing +@code{ 0 0 -DO i . 1 -LOOP} prints nothing -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. +Another alternative is @code{@var{n} S+LOOP}, where the negative +case behaves symmetrical to the positive case: -@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. +@code{-2 0 -DO i . -1 S+LOOP} prints @code{0 -1} + +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 +878,7 @@ 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 +889,7 @@ 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 +905,7 @@ 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 +920,16 @@ 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 +1000,8 @@ 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 @@ -977,12 +1027,12 @@ locals wordset, but also our own, more p implemented the ANS Forth locals wordset through our locals wordset). @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 +1075,7 @@ 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 +1095,7 @@ 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 +1105,7 @@ 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 +1227,10 @@ 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 +1264,7 @@ 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 +1278,7 @@ 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 +1292,7 @@ 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 +1347,10 @@ 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 +1385,7 @@ 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 +1475,12 @@ 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 +1496,13 @@ 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 +1513,7 @@ 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 +1528,7 @@ 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 +1557,7 @@ 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 +1602,7 @@ 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 +1625,7 @@ 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 +1656,47 @@ 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 gcc version and options used. + +The words 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 it with @code{require code.fs}. + +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) probably 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 +1710,25 @@ 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 +1750,7 @@ 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 +1763,7 @@ 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 +1802,7 @@ 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 +1827,10 @@ 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 +1890,19 @@ 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 +1938,7 @@ 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: @@ -2216,7 +2316,7 @@ 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. @@ -2647,13 +2747,13 @@ 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 +2763,7 @@ 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 +2775,7 @@ 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 +2786,18 @@ 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. @menu * Portability:: * Threading:: * Primitives:: * System Architecture:: +* Performance:: @end menu @node Portability, Threading, Internals, Internals @@ -2728,9 +2829,7 @@ 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 +3120,7 @@ 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 +3143,7 @@ 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 +3163,130 @@ 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 (compiled with @code{gcc-2.6.3} and @code{-DFORCE_REG}) with +Win32Forth 1.2093 and LMI's NT Forth (Beta, May 1994), two systems +written in assembly, and 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). 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. + +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 benchmark 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 This- + time Gforth Forth Forth PFE Forth +sieve 1.00 1.30 1.07 1.67 2.98 +bubble 1.00 1.30 1.40 1.66 +matmul 1.00 1.40 1.29 2.24 +fib 1.00 1.44 1.26 1.82 2.82 +@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}). + +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. + @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 !!. 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 (!! a way to find them out), 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 child of VolksForth. + +VolksForth descends from F83. !! Authors? When? + +Laxen and 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. Dean Sanderson and Bill Ragsdale developed the original +implementation of fig-Forth based on microForth. + +!! microForth pedigree + +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