version 1.33, 1996/05/13 16:36:56
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version 1.36, 1996/09/23 08:52:47
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Line 88 personal machines. This manual correspon
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Line 88 personal machines. This manual correspon
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* Words:: Forth words available in Gforth |
* Words:: Forth words available in Gforth |
* ANS conformance:: Implementation-defined options etc. |
* ANS conformance:: Implementation-defined options etc. |
* Model:: The abstract machine of Gforth |
* Model:: The abstract machine of Gforth |
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* Integrating Gforth:: Forth as scripting language for applications. |
* Emacs and Gforth:: The Gforth Mode |
* Emacs and Gforth:: The Gforth Mode |
* Internals:: Implementation details |
* Internals:: Implementation details |
* Bugs:: How to report them |
* Bugs:: How to report them |
Line 754 double sized signed integer
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Line 755 double sized signed integer
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@item ud |
@item ud |
double sized unsigned integer |
double sized unsigned integer |
@item r |
@item r |
Float |
Float (on the FP stack) |
@item a_ |
@item a_ |
Cell-aligned address |
Cell-aligned address |
@item c_ |
@item c_ |
Char-aligned address (note that a Char is two bytes in Windows NT) |
Char-aligned address (note that a Char may have two bytes in Windows NT) |
@item f_ |
@item f_ |
Float-aligned address |
Float-aligned address |
@item df_ |
@item df_ |
Line 771 Execution token, same size as Cell
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Line 772 Execution token, same size as Cell
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Wordlist ID, same size as Cell |
Wordlist ID, same size as Cell |
@item f83name |
@item f83name |
Pointer to a name structure |
Pointer to a name structure |
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@item " |
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string in the input stream (not the stack). The terminating character is |
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a blank by default. If it is not a blank, it is shown in @code{<>} |
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quotes. |
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@end table |
@end table |
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@node Arithmetic, Stack Manipulation, Notation, Words |
@node Arithmetic, Stack Manipulation, Notation, Words |
Line 848 The format of floating point numbers rec
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Line 854 The format of floating point numbers rec
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interpreter is: a signed decimal number, possibly containing a decimal |
interpreter is: a signed decimal number, possibly containing a decimal |
point (@code{.}), followed by @code{E} or @code{e}, optionally followed |
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 |
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} |
@code{+1.0e+0}. Note that a number without @code{e} |
is not interpreted as floating-point number, but as double (if the |
is not interpreted as floating-point number, but as double (if the |
number contains a @code{.}) or single precision integer. Also, |
number contains a @code{.}) or single precision integer. Also, |
conversions between string and floating point numbers always use base |
conversions between string and floating point numbers always use base |
Line 1733 E.g., a definition using @code{TO} might
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Line 1739 E.g., a definition using @code{TO} might
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: strcmp @{ addr1 u1 addr2 u2 -- n @} |
: strcmp @{ addr1 u1 addr2 u2 -- n @} |
u1 u2 min 0 |
u1 u2 min 0 |
?do |
?do |
addr1 c@ addr2 c@ - |
addr1 c@@ addr2 c@@ - |
?dup-if |
?dup-if |
unloop exit |
unloop exit |
then |
then |
Line 1756 are initialized with the right value for
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Line 1762 are initialized with the right value for
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addr1 addr2 |
addr1 addr2 |
u1 u2 min 0 |
u1 u2 min 0 |
?do @{ s1 s2 @} |
?do @{ s1 s2 @} |
s1 c@ s2 c@ - |
s1 c@@ s2 c@@ - |
?dup-if |
?dup-if |
unloop exit |
unloop exit |
then |
then |
Line 1930 stack easier.
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Line 1936 stack easier.
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The whole definition must be in one line. |
The whole definition must be in one line. |
@end itemize |
@end itemize |
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Locals defined in this way behave like @code{VALUE}s |
Locals defined in this way behave like @code{VALUE}s (@xref{Simple |
(@xref{Values}). I.e., they are initialized from the stack. Using their |
Defining Words}). I.e., they are initialized from the stack. Using their |
name produces their value. Their value can be changed using @code{TO}. |
name produces their value. Their value can be changed using @code{TO}. |
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Since this syntax is supported by Gforth directly, you need not do |
Since this syntax is supported by Gforth directly, you need not do |
Line 1960 locals wordset.
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Line 1966 locals wordset.
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@section Defining Words |
@section Defining Words |
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@menu |
@menu |
* Values:: |
* Simple Defining Words:: |
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* Colon Definitions:: |
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* User-defined Defining Words:: |
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* Supplying names:: |
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* Interpretation and Compilation Semantics:: |
@end menu |
@end menu |
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@node Values, , Defining Words, Defining Words |
@node Simple Defining Words, Colon Definitions, Defining Words, Defining Words |
@subsection Values |
@subsection Simple Defining Words |
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doc-constant |
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doc-2constant |
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doc-fconstant |
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doc-variable |
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doc-2variable |
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doc-fvariable |
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doc-create |
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doc-user |
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doc-value |
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doc-to |
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doc-defer |
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doc-is |
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@node Colon Definitions, User-defined Defining Words, Simple Defining Words, Defining Words |
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@subsection Colon Definitions |
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@example |
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: name ( ... -- ... ) |
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word1 word2 word3 ; |
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@end example |
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creates a word called @code{name}, that, upon execution, executes |
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@code{word1 word2 word3}. @code{name} is a @dfn{(colon) definition}. |
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The explanation above is somewhat superficial. @xref{Interpretation and |
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Compilation Semantics} for an in-depth discussion of some of the issues |
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involved. |
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doc-: |
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doc-; |
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@node User-defined Defining Words, Supplying names, Colon Definitions, Defining Words |
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@subsection User-defined Defining Words |
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You can create new defining words simply by wrapping defining-time code |
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around existing defining words and putting the sequence in a colon |
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definition. |
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If you want the words defined with your defining words to behave |
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differently from words defined with standard defining words, you can |
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write your defining word like this: |
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@example |
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: def-word ( "name" -- ) |
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Create @var{code1} |
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DOES> ( ... -- ... ) |
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@var{code2} ; |
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def-word name |
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@end example |
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Technically, this fragment defines a defining word @code{def-word}, and |
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a word @code{name}; when you execute @code{name}, the address of the |
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body of @code{name} is put on the data stack and @var{code2} is executed |
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(the address of the body of @code{name} is the address @code{HERE} |
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returns immediately after the @code{CREATE}). |
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In other words, if you make the following definitions: |
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@example |
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: def-word1 ( "name" -- ) |
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Create @var{code1} ; |
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: action1 ( ... -- ... ) |
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@var{code2} ; |
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def-word name1 |
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@end example |
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Using @code{name1 action1} is equivalent to using @code{name}. |
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E.g., you can implement @code{Constant} in this way: |
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@example |
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: constant ( w "name" -- ) |
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create , |
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DOES> ( -- w ) |
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@@ ; |
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@end example |
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When you create a constant with @code{5 constant five}, first a new word |
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@code{five} is created, then the value 5 is laid down in the body of |
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@code{five} with @code{,}. When @code{five} is invoked, the address of |
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the body is put on the stack, and @code{@@} retrieves the value 5. |
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In the example above the stack comment after the @code{DOES>} specifies |
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the stack effect of the defined words, not the stack effect of the |
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following code (the following code expects the address of the body on |
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the top of stack, which is not reflected in the stack comment). This is |
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the convention that I use and recommend (it clashes a bit with using |
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locals declarations for stack effect specification, though). |
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@subsubsection Applications of @code{CREATE..DOES>} |
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You may wonder how to use this feature. Here are some usage patterns: |
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When you see a sequence of code occurring several times, and you can |
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identify a meaning, you will factor it out as a colon definition. When |
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you see similar colon definitions, you can factor them using |
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@code{CREATE..DOES>}. E.g., an assembler usually defines several words |
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that look very similar: |
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@example |
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: ori, ( reg-taget reg-source n -- ) |
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0 asm-reg-reg-imm ; |
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: andi, ( reg-taget reg-source n -- ) |
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1 asm-reg-reg-imm ; |
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@end example |
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This could be factored with: |
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@example |
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: reg-reg-imm ( op-code -- ) |
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create , |
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DOES> ( reg-taget reg-source n -- ) |
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@@ asm-reg-reg-imm ; |
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0 reg-reg-imm ori, |
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1 reg-reg-imm andi, |
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@end example |
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Another view of @code{CREATE..DOES>} is to consider it as a crude way to |
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supply a part of the parameters for a word (known as @dfn{currying} in |
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the functional language community). E.g., @code{+} needs two |
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parameters. Creating versions of @code{+} with one parameter fixed can |
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be done like this: |
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@example |
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: curry+ ( n1 -- ) |
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create , |
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DOES> ( n2 -- n1+n2 ) |
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@@ + ; |
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3 curry+ 3+ |
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-2 curry+ 2- |
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@end example |
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@subsubsection The gory details of @code{CREATE..DOES>} |
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doc-does> |
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This means that you need not use @code{CREATE} and @code{DOES>} in the |
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same definition; E.g., you can put the @code{DOES>}-part in a separate |
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definition. This allows us to, e.g., select among different DOES>-parts: |
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@example |
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: does1 |
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DOES> ( ... -- ... ) |
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... ; |
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: does2 |
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DOES> ( ... -- ... ) |
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... ; |
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: def-word ( ... -- ... ) |
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create ... |
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IF |
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does1 |
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ELSE |
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does2 |
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ENDIF ; |
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@end example |
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In a standard program you can apply a @code{DOES>}-part only if the last |
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word was defined with @code{CREATE}. In Gforth, the @code{DOES>}-part |
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will override the behaviour of the last word defined in any case. In a |
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standard program, you can use @code{DOES>} only in a colon |
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definition. In Gforth, you can also use it in interpretation state, in a |
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kind of one-shot mode: |
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@example |
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CREATE name ( ... -- ... ) |
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@var{initialization} |
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DOES> |
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@var{code} ; |
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@end example |
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This is equivalwent to the standard |
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@example |
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:noname |
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DOES> |
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@var{code} ; |
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CREATE name EXECUTE ( ... -- ... ) |
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@var{initialization} |
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@end example |
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You can get the address of the body of a word with |
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doc->body |
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@node Supplying names, Interpretation and Compilation Semantics, User-defined Defining Words, Defining Words |
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@subsection Supplying names for the defined words |
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By default, defining words take the names for the defined words from the |
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input stream. Sometimes you want to supply the name from a string. You |
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can do this with |
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doc-nextname |
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E.g., |
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@example |
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s" foo" nextname create |
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@end example |
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is equivalent to |
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@example |
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create foo |
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@end example |
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Sometimes you want to define a word without a name. You can do this with |
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doc-noname |
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To make any use of the newly defined word, you need its execution |
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token. You can get it with |
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doc-lastxt |
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E.g., you can initialize a deferred word with an anonymous colon |
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definition: |
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@example |
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Defer deferred |
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noname : ( ... -- ... ) |
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... ; |
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lastxt IS deferred |
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@end example |
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@code{lastxt} also works when the last word was not defined as |
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@code{noname}. |
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The standard has also recognized the need for anonymous words and |
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provides |
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doc-:noname |
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This leaves the execution token for the word on the stack after the |
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closing @code{;}. You can rewrite the last example with @code{:noname}: |
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@example |
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Defer deferred |
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:noname ( ... -- ... ) |
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... ; |
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IS deferred |
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@end example |
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@node Interpretation and Compilation Semantics, , Supplying names, Defining Words |
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@subsection Interpretation and Compilation Semantics |
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The @dfn{interpretation semantics} of a word are what the text |
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interpreter does when it encounters the word in interpret state. It also |
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appears in some other contexts, e.g., the execution token returned by |
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@code{' @var{word}} identifies the interpretation semantics of |
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@var{word} (in other words, @code{' @var{word} execute} is equivalent to |
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interpret-state text interpretation of @code{@var{word}}). |
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The @dfn{compilation semantics} of a word are what the text interpreter |
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does when it encounters the word in compile state. It also appears in |
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other contexts, e.g, @code{POSTPONE @var{word}} compiles@footnote{In |
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standard terminology, ``appends to the current definition''.} the |
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compilation semantics of @var{word}. |
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The standard also talks about @dfn{execution semantics}. They are used |
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only for defining the interpretation and compilation semantics of many |
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words. By default, the interpretation semantics of a word are to |
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@code{execute} its execution semantics, and the compilation semantics of |
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a word are to @code{compile,} its execution semantics.@footnote{In |
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standard terminology: The default interpretation semantics are its |
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execution semantics; the default compilation semantics are to append its |
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execution semantics to the execution semantics of the current |
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definition.} |
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You can change the compilation semantics into @code{execute}ing the |
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execution semantics with |
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doc-immediate |
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You can remove the interpretation semantics of a word with |
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doc-compile-only |
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doc-restrict |
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Note that ticking (@code{'}) compile-only words gives an error |
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(``Interpreting a compile-only word''). |
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Gforth also allows you to define words with arbitrary combinations of |
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interpretation and compilation semantics. |
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doc-interpret/compile: |
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This feature was introduced for implementing @code{TO} and @code{S"}. I |
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recommend that you do not define such words, as cute as they may be: |
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they make it hard to get at both parts of the word in some contexts. |
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E.g., assume you want to get an execution token for the compilation |
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part. Instead, define two words, one that embodies the interpretation |
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part, and one that embodies the compilation part. |
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There is, however, a potentially useful application of this feature: |
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Providing differing implementations for the default semantics. While |
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this introduces redundancy and is therefore usually a bad idea, a |
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performance improvement may be worth the trouble. E.g., consider the |
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word @code{foobar}: |
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@example |
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: foobar |
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foo bar ; |
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@end example |
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Let us assume that @code{foobar} is called so frequently that the |
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calling overhead would take a significant amount of the run-time. We can |
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optimize it with @code{interpret/compile:}: |
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@example |
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:noname |
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foo bar ; |
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:noname |
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POSTPONE foo POSTPONE bar ; |
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interpret/compile: foobar |
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@end example |
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This definition has the same interpretation semantics and essentially |
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the same compilation semantics as the simple definition of |
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@code{foobar}, but the implementation of the compilation semantics is |
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more efficient with respect to run-time. |
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Some people try to use state-smart words to emulate the feature provided |
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by @code{interpret/compile:} (words are state-smart if they check |
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@code{STATE} during execution). E.g., they would try to code |
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@code{foobar} like this: |
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@example |
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: foobar |
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STATE @@ |
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IF ( compilation state ) |
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POSTPONE foo POSTPONE bar |
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ELSE |
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foo bar |
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ENDIF ; immediate |
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@end example |
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While this works if @code{foobar} is processed only by the text |
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interpreter, it does not work in other contexts (like @code{'} or |
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@code{POSTPONE}). E.g., @code{' foobar} will produce an execution token |
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for a state-smart word, not for the interpretation semantics of the |
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original @code{foobar}; when you execute this execution token (directly |
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with @code{EXECUTE} or indirectly through @code{COMPILE,}) in compile |
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state, the result will not be what you expected (i.e., it will not |
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perform @code{foo bar}). State-smart words are a bad idea. Simply don't |
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write them! |
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It is also possible to write defining words that define words with |
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arbitrary combinations of interpretation and compilation semantics (or, |
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preferably, arbitrary combinations of implementations of the default |
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semantics). In general, this looks like: |
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@example |
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: def-word |
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create-interpret/compile |
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@var{code1} |
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interpretation> |
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@var{code2} |
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<interpretation |
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compilation> |
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@var{code3} |
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<compilation ; |
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@end example |
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For a @var{word} defined with @code{def-word}, the interpretation |
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semantics are to push the address of the body of @var{word} and perform |
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@var{code2}, and the compilation semantics are to push the address of |
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the body of @var{word} and perform @var{code3}. E.g., @code{constant} |
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can also be defined like this: |
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@example |
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: constant ( n "name" -- ) |
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create-interpret/compile |
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, |
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interpretation> ( -- n ) |
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@@ |
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<interpretation |
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compilation> ( compilation. -- ; run-time. -- n ) |
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@@ postpone literal |
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<compilation ; |
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@end example |
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doc-create-interpret/compile |
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doc-interpretation> |
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doc-<interpretation |
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doc-compilation> |
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doc-<compilation |
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Note that words defined with @code{interpret/compile:} and |
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@code{create-interpret/compile} have an extended header structure that |
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differs from other words; however, unless you try to access them with |
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plain address arithmetic, you should not notice this. Words for |
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accessing the header structure usually know how to deal with this; e.g., |
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@code{' word >body} also gives you the body of a word created with |
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@code{create-interpret/compile}. |
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@node Wordlists, Files, Defining Words, Words |
@node Wordlists, Files, Defining Words, Words |
@section Wordlists |
@section Wordlists |
Line 2140 and use that in your assembly code.
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Line 2541 and use that in your assembly code.
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Another option for implementing normal and defining words efficiently |
Another option for implementing normal and defining words efficiently |
is: adding the wanted functionality to the source of Gforth. For normal |
is: adding the wanted functionality to the source of Gforth. For normal |
words you just have to edit @file{primitives}, defining words (for fast |
words you just have to edit @file{primitives} (@pxref{Automatic |
defined words) may require changes in @file{engine.c}, |
Generation}), defining words (equivalent to @code{;CODE} words, for fast |
@file{kernal.fs}, @file{prims2x.fs}, and possibly @file{cross.fs}. |
defined words) may require changes in @file{engine.c}, @file{kernal.fs}, |
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@file{prims2x.fs}, and possibly @file{cross.fs}. |
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@node Threading Words, , Assembler and Code words, Words |
@node Threading Words, , Assembler and Code words, Words |
Line 2173 doc-douser:
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Line 2575 doc-douser:
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doc-dodefer: |
doc-dodefer: |
doc-dofield: |
doc-dofield: |
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Currently there is no installation-independent way for recogizing words |
You can recognize words defined by a @code{CREATE}...@code{DOES>} word |
defined by a @code{CREATE}...@code{DOES>} word; however, once you know |
with @code{>DOES-CODE}. If the word was defined in that way, the value |
that a word is defined by a @code{CREATE}...@code{DOES>} word, you can |
returned is different from 0 and identifies the @code{DOES>} used by the |
use @code{>DOES-CODE}. |
defining word. |
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@node ANS conformance, Model, Words, Top |
@node ANS conformance, Model, Words, Top |
@chapter ANS conformance |
@chapter ANS conformance |
Line 2184 use @code{>DOES-CODE}.
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Line 2586 use @code{>DOES-CODE}.
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To the best of our knowledge, Gforth is an |
To the best of our knowledge, Gforth is an |
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ANS Forth System |
ANS Forth System |
@itemize |
@itemize @bullet |
@item providing the Core Extensions word set |
@item providing the Core Extensions word set |
@item providing the Block word set |
@item providing the Block word set |
@item providing the Block Extensions word set |
@item providing the Block Extensions word set |
Line 2203 ANS Forth System
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Line 2605 ANS Forth System
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@item providing the Memory-Allocation word set |
@item providing the Memory-Allocation word set |
@item providing the Memory-Allocation Extensions word set (that one's easy) |
@item providing the Memory-Allocation Extensions word set (that one's easy) |
@item providing the Programming-Tools word set |
@item providing the Programming-Tools 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 @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 word set |
@item providing the Search-Order Extensions word set |
@item providing the Search-Order Extensions word set |
@item providing the String word set |
@item providing the String word set |
Line 2261 processor-dependent. Gforth's alignment
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Line 2663 processor-dependent. Gforth's alignment
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@item @code{EMIT} and non-graphic characters: |
@item @code{EMIT} and non-graphic characters: |
The character is output using the C library function (actually, macro) |
The character is output using the C library function (actually, macro) |
@code{putchar}. |
@code{putc}. |
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|
@item character editing of @code{ACCEPT} and @code{EXPECT}: |
@item character editing of @code{ACCEPT} and @code{EXPECT}: |
This is modeled on the GNU readline library (@pxref{Readline |
This is modeled on the GNU readline library (@pxref{Readline |
Line 2281 installation-dependent. Currently a char
|
Line 2683 installation-dependent. Currently a char
|
|
|
@item character-set extensions and matching of names: |
@item character-set extensions and matching of names: |
Any character except the ASCII NUL charcter can be used in a |
Any character except the ASCII NUL charcter can be used in a |
name. Matching is case-insensitive. The matching is performed using the |
name. Matching is case-insensitive (except in @code{TABLE}s. The |
C function @code{strncasecmp}, whose function is probably influenced by |
matching is performed using the C function @code{strncasecmp}, whose |
the locale. E.g., the @code{C} locale does not know about accents and |
function is probably influenced by the locale. E.g., the @code{C} locale |
umlauts, so they are matched case-sensitively in that locale. For |
does not know about accents and umlauts, so they are matched |
portability reasons it is best to write programs such that they work in |
case-sensitively in that locale. For portability reasons it is best to |
the @code{C} locale. Then one can use libraries written by a Polish |
write programs such that they work in the @code{C} locale. Then one can |
programmer (who might use words containing ISO Latin-2 encoded |
use libraries written by a Polish programmer (who might use words |
characters) and by a French programmer (ISO Latin-1) in the same program |
containing ISO Latin-2 encoded characters) and by a French programmer |
(of course, @code{WORDS} will produce funny results for some of the |
(ISO Latin-1) in the same program (of course, @code{WORDS} will produce |
words (which ones, depends on the font you are using)). Also, the locale |
funny results for some of the words (which ones, depends on the font you |
you prefer may not be available in other operating systems. Hopefully, |
are using)). Also, the locale you prefer may not be available in other |
Unicode will solve these problems one day. |
operating systems. Hopefully, Unicode will solve these problems one day. |
|
|
@item conditions under which control characters match a space delimiter: |
@item conditions under which control characters match a space delimiter: |
If @code{WORD} is called with the space character as a delimiter, all |
If @code{WORD} is called with the space character as a delimiter, all |
Line 2325 The error string is stored into the vari
|
Line 2727 The error string is stored into the vari
|
@code{-2 throw} is performed. |
@code{-2 throw} is performed. |
|
|
@item input line terminator: |
@item input line terminator: |
For interactive input, @kbd{C-m} and @kbd{C-j} terminate lines. One of |
For interactive input, @kbd{C-m} (CR) and @kbd{C-j} (LF) terminate |
these characters is typically produced when you type the @kbd{Enter} or |
lines. One of these characters is typically produced when you type the |
@kbd{Return} key. |
@kbd{Enter} or @kbd{Return} key. |
|
|
@item maximum size of a counted string: |
@item maximum size of a counted string: |
@code{s" /counted-string" environment? drop .}. Currently 255 characters |
@code{s" /counted-string" environment? drop .}. Currently 255 characters |
Line 2348 change it from within Gforth. However, t
|
Line 2750 change it from within Gforth. However, t
|
redirected in the command line that starts Gforth. |
redirected in the command line that starts Gforth. |
|
|
@item method of selecting the user output device: |
@item method of selecting the user output device: |
The user output device is the standard output. It cannot be redirected |
@code{EMIT} and @code{TYPE} output to the file-id stored in the value |
from within Gforth, but typically from the command line that starts |
@code{outfile-id} (@code{stdout} by default). Gforth uses buffered |
Gforth. Gforth uses buffered output, so output on a terminal does not |
output, so output on a terminal does not become visible before the next |
become visible before the next newline or buffer overflow. Output on |
newline or buffer overflow. Output on non-terminals is invisible until |
non-terminals is invisible until the buffer overflows. |
the buffer overflows. |
|
|
@item methods of dictionary compilation: |
@item methods of dictionary compilation: |
What are we expected to document here? |
What are we expected to document here? |
Line 2388 string.
|
Line 2790 string.
|
@code{1 chars .}. 1 on all current ports. |
@code{1 chars .}. 1 on all current ports. |
|
|
@item size of the keyboard terminal buffer: |
@item size of the keyboard terminal buffer: |
Varies. You can determine the size at a specific time using @code{lp@ |
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 |
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 |
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 |
Line 2400 shared with @code{WORD}.
|
Line 2802 shared with @code{WORD}.
|
|
|
@item size of the scratch area returned by @code{PAD}: |
@item size of the scratch area returned by @code{PAD}: |
The remainder of dictionary space. You can even use the unused part of |
The remainder of dictionary space. You can even use the unused part of |
the data stack space. The current size can be computed with @code{sp@ |
the data stack space. The current size can be computed with @code{sp@@ |
pad - .}. |
pad - .}. |
|
|
@item system case-sensitivity characteristics: |
@item system case-sensitivity characteristics: |
Dictionary searches are case insensitive. However, as explained above |
Dictionary searches are case insensitive (except in |
under @i{character-set extensions}, the matching for non-ASCII |
@code{TABLE}s). However, as explained above under @i{character-set |
characters is determined by the locale you are using. In the default |
extensions}, the matching for non-ASCII characters is determined by the |
@code{C} locale all non-ASCII characters are matched case-sensitively. |
locale you are using. In the default @code{C} locale all non-ASCII |
|
characters are matched case-sensitively. |
|
|
@item system prompt: |
@item system prompt: |
@code{ ok} in interpret state, @code{ compiled} in compile state. |
@code{ ok} in interpret state, @code{ compiled} in compile state. |
Line 2424 the choice to @code{gcc} (what to use fo
|
Line 2827 the choice to @code{gcc} (what to use fo
|
On two's complement machines, arithmetic is performed modulo |
On two's complement machines, arithmetic is performed modulo |
2**bits-per-cell for single arithmetic and 4**bits-per-cell for double |
2**bits-per-cell for single arithmetic and 4**bits-per-cell for double |
arithmetic (with appropriate mapping for signed types). Division by zero |
arithmetic (with appropriate mapping for signed types). Division by zero |
typically results in a @code{-55 throw} (floatingpoint unidentified |
typically results in a @code{-55 throw} (Floating-point unidentified |
fault), although a @code{-10 throw} (divide by zero) would be more |
fault), although a @code{-10 throw} (divide by zero) would be more |
appropriate. |
appropriate. |
|
|
Line 2441 No.
|
Line 2844 No.
|
@table @i |
@table @i |
|
|
@item a name is neither a word nor a number: |
@item a name is neither a word nor a number: |
@code{-13 throw} (Undefined word) |
@code{-13 throw} (Undefined word). Actually, @code{-13 bounce}, which |
|
preserves the data and FP stack, so you don't lose more work than |
|
necessary. |
|
|
@item a definition name exceeds the maximum length allowed: |
@item a definition name exceeds the maximum length allowed: |
@code{-19 throw} (Word name too long) |
@code{-19 throw} (Word name too long) |
Line 2458 flow words, and issue a @code{ABORT"} or
|
Line 2863 flow words, and issue a @code{ABORT"} or
|
mismatch). |
mismatch). |
|
|
@item attempting to obtain the execution token of a word with undefined execution semantics: |
@item attempting to obtain the execution token of a word with undefined execution semantics: |
You get an execution token representing the compilation semantics |
@code{-14 throw} (Interpreting a compile-only word). In some cases, you |
instead. |
get an execution token for @code{compile-only-error} (which performs a |
|
@code{-14 throw} when executed). |
|
|
@item dividing by zero: |
@item dividing by zero: |
typically results in a @code{-55 throw} (floating point unidentified |
typically results in a @code{-55 throw} (floating point unidentified |
Line 2480 error appears at a different place when
|
Line 2886 error appears at a different place when
|
|
|
@item interpreting a word with undefined interpretation semantics: |
@item interpreting a word with undefined interpretation semantics: |
For some words, we defined interpretation semantics. For the others: |
For some words, we defined interpretation semantics. For the others: |
@code{-14 throw} (Interpreting a compile-only word). Note that this is |
@code{-14 throw} (Interpreting a compile-only word). |
checked only by the outer (aka text) interpreter; if the word is |
|
@code{execute}d in some other way, it will typically perform it's |
|
compilation semantics even in interpret state. (We could change @code{'} |
|
and relatives not to give the xt of such words, but we think that would |
|
be too restrictive). |
|
|
|
@item modifying the contents of the input buffer or a string literal: |
@item modifying the contents of the input buffer or a string literal: |
These are located in writable memory and can be modified. |
These are located in writable memory and can be modified. |
Line 2512 underflow) is performed. Apart from that
|
Line 2913 underflow) is performed. Apart from that
|
underflows can result in similar behaviour as overflows (of adjacent |
underflows can result in similar behaviour as overflows (of adjacent |
stacks). |
stacks). |
|
|
@item unexepected end of the input buffer, resulting in an attempt to use a zero-length string as a name: |
@item unexpected end of the input buffer, resulting in an attempt to use a zero-length string as a name: |
@code{Create} and its descendants perform a @code{-16 throw} (Attempt to |
@code{Create} and its descendants perform a @code{-16 throw} (Attempt to |
use zero-length string as a name). Words like @code{'} probably will not |
use zero-length string as a name). Words like @code{'} probably will not |
find what they search. Note that it is possible to create zero-length |
find what they search. Note that it is possible to create zero-length |
Line 2522 names with @code{nextname} (should it no
|
Line 2923 names with @code{nextname} (should it no
|
The next invocation of a parsing word returns a string wih length 0. |
The next invocation of a parsing word returns a string wih length 0. |
|
|
@item @code{RECURSE} appears after @code{DOES>}: |
@item @code{RECURSE} appears after @code{DOES>}: |
Compiles a recursive call to the defining word not to the defined word. |
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}: |
@item argument input source different than current input source for @code{RESTORE-INPUT}: |
@code{-12 THROW}. Note that, once an input file is closed (e.g., because |
@code{-12 THROW}. Note that, once an input file is closed (e.g., because |
Line 2531 reused. Therefore, restoring an input so
|
Line 2932 reused. Therefore, restoring an input so
|
closed file may lead to unpredictable results instead of a @code{-12 |
closed file may lead to unpredictable results instead of a @code{-12 |
THROW}. |
THROW}. |
|
|
In the future, Gforth may be able to retore input source specifications |
In the future, Gforth may be able to restore input source specifications |
from other than the current input soruce. |
from other than the current input soruce. |
|
|
@item data space containing definitions gets de-allocated: |
@item data space containing definitions gets de-allocated: |
Line 2559 stack items are loop control parameters
|
Line 2960 stack items are loop control parameters
|
@code{abort" last word was headerless"}. |
@code{abort" last word was headerless"}. |
|
|
@item name not defined by @code{VALUE} used by @code{TO}: |
@item name not defined by @code{VALUE} used by @code{TO}: |
@code{-32 throw} (Invalid name argument) |
@code{-32 throw} (Invalid name argument) (unless name was defined by |
|
@code{CONSTANT}; then it just changes the constant). |
|
|
@item name not found (@code{'}, @code{POSTPONE}, @code{[']}, @code{[COMPILE]}): |
@item name not found (@code{'}, @code{POSTPONE}, @code{[']}, @code{[COMPILE]}): |
@code{-13 throw} (Undefined word) |
@code{-13 throw} (Undefined word) |
Line 2569 Gforth behaves as if they were of the sa
|
Line 2971 Gforth behaves as if they were of the sa
|
the behaviour by interpreting all parameters as, e.g., signed. |
the behaviour by interpreting all parameters as, e.g., signed. |
|
|
@item @code{POSTPONE} or @code{[COMPILE]} applied to @code{TO}: |
@item @code{POSTPONE} or @code{[COMPILE]} applied to @code{TO}: |
Assume @code{: X POSTPONE TO ; IMMEDIATE}. @code{X} is equivalent to |
Assume @code{: X POSTPONE TO ; IMMEDIATE}. @code{X} performs the |
@code{TO}. |
compilation semantics of @code{TO}. |
|
|
@item String longer than a counted string returned by @code{WORD}: |
@item String longer than a counted string returned by @code{WORD}: |
Not checked. The string will be ok, but the count will, of course, |
Not checked. The string will be ok, but the count will, of course, |
Line 2609 and you can give commands to Gforth inte
|
Line 3011 and you can give commands to Gforth inte
|
available depend on how you invoke Gforth. |
available depend on how you invoke Gforth. |
|
|
@item program data space available: |
@item program data space available: |
@code{sp@ here - .} gives the space remaining for dictionary and data |
@code{sp@@ here - .} gives the space remaining for dictionary and data |
stack together. |
stack together. |
|
|
@item return stack space available: |
@item return stack space available: |
Line 2617 By default 16 KBytes. The default can be
|
Line 3019 By default 16 KBytes. The default can be
|
switch (@pxref{Invocation}) when Gforth starts up. |
switch (@pxref{Invocation}) when Gforth starts up. |
|
|
@item stack space available: |
@item stack space available: |
@code{sp@ here - .} gives the space remaining for dictionary and data |
@code{sp@@ here - .} gives the space remaining for dictionary and data |
stack together. |
stack together. |
|
|
@item system dictionary space required, in address units: |
@item system dictionary space required, in address units: |
Line 3212 are applied to the latest defined word (
|
Line 3614 are applied to the latest defined word (
|
|
|
@end table |
@end table |
|
|
|
@node Model, Integrating Gforth, ANS conformance, Top |
@node Model, Emacs and Gforth, ANS conformance, Top |
|
@chapter Model |
@chapter Model |
|
|
@node Emacs and Gforth, Internals, Model, Top |
This chapter has yet to be written. It will contain information, on |
|
which internal structures you can rely. |
|
|
|
@node Integrating Gforth, Emacs and Gforth, Model, Top |
|
@chapter Integrating Gforth into C programs |
|
|
|
This is not yet implemented. |
|
|
|
Several people like to use Forth as scripting language for applications |
|
that are otherwise written in C, C++, or some other language. |
|
|
|
The Forth system ATLAST provides facilities for embedding it into |
|
applications; unfortunately it has several disadvantages: most |
|
importantly, it is not based on ANS Forth, and it is apparently dead |
|
(i.e., not developed further and not supported). The facilities |
|
provided by Gforth in this area are inspired by ATLASTs facilities, so |
|
making the switch should not be hard. |
|
|
|
We also tried to design the interface such that it can easily be |
|
implemented by other Forth systems, so that we may one day arrive at a |
|
standardized interface. Such a standard interface would allow you to |
|
replace the Forth system without having to rewrite C code. |
|
|
|
You embed the Gforth interpreter by linking with the library |
|
@code{libgforth.a} (give the compiler the option @code{-lgforth}). All |
|
global symbols in this library that belong to the interface, have the |
|
prefix @code{forth_}. (Global symbols that are used internally have the |
|
prefix @code{gforth_}). |
|
|
|
You can include the declarations of Forth types and the functions and |
|
variables of the interface with @code{#include <forth.h>}. |
|
|
|
Types. |
|
|
|
Variables. |
|
|
|
Data and FP Stack pointer. Area sizes. |
|
|
|
functions. |
|
|
|
forth_init(imagefile) |
|
forth_evaluate(string) exceptions? |
|
forth_goto(address) (or forth_execute(xt)?) |
|
forth_continue() (a corountining mechanism) |
|
|
|
Adding primitives. |
|
|
|
No checking. |
|
|
|
Signals? |
|
|
|
Accessing the Stacks |
|
|
|
@node Emacs and Gforth, Internals, Integrating Gforth, Top |
@chapter Emacs and Gforth |
@chapter Emacs and Gforth |
|
|
Gforth comes with @file{gforth.el}, an improved version of |
Gforth comes with @file{gforth.el}, an improved version of |
Line 3549 An important optimization for stack mach
|
Line 4003 An important optimization for stack mach
|
engines, is keeping one or more of the top stack items in |
engines, is keeping one or more of the top stack items in |
registers. If a word has the stack effect @var{in1}...@var{inx} @code{--} |
registers. If a word has the stack effect @var{in1}...@var{inx} @code{--} |
@var{out1}...@var{outy}, keeping the top @var{n} items in registers |
@var{out1}...@var{outy}, keeping the top @var{n} items in registers |
@itemize |
@itemize @bullet |
@item |
@item |
is better than keeping @var{n-1} items, if @var{x>=n} and @var{y>=n}, |
is better than keeping @var{n-1} items, if @var{x>=n} and @var{y>=n}, |
due to fewer loads from and stores to the stack. |
due to fewer loads from and stores to the stack. |
Line 3583 The TOS optimization makes the automatic
|
Line 4037 The TOS optimization makes the automatic
|
bit more complicated. Just replacing all occurrences of @code{sp[0]} by |
bit more complicated. Just replacing all occurrences of @code{sp[0]} by |
@code{TOS} is not sufficient. There are some special cases to |
@code{TOS} is not sufficient. There are some special cases to |
consider: |
consider: |
@itemize |
@itemize @bullet |
@item In the case of @code{dup ( w -- w w )} the generator must not |
@item In the case of @code{dup ( w -- w w )} the generator must not |
eliminate the store to the original location of the item on the stack, |
eliminate the store to the original location of the item on the stack, |
if the TOS optimization is turned on. |
if the TOS optimization is turned on. |
Line 3785 VolksForth descends from F83. It was wri
|
Line 4239 VolksForth descends from F83. It was wri
|
Pennemann, Georg Rehfeld and Dietrich Weineck for the C64 (called |
Pennemann, Georg Rehfeld and Dietrich Weineck for the C64 (called |
UltraForth there) in the mid-80s and ported to the Atari ST in 1986. |
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 |
Henry Laxen and Mike Perry wrote F83 as a model implementation of the |
Forth-83 standard. !! Pedigree? When? |
Forth-83 standard. !! Pedigree? When? |
|
|
A team led by Bill Ragsdale implemented fig-Forth on many processors in |
A team led by Bill Ragsdale implemented fig-Forth on many processors in |