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1 | %%% -*-latex-*- |
2 | %%% | |
3 | %%% Module syntax | |
4 | %%% | |
5 | %%% (c) 2015 Straylight/Edgeware | |
6 | %%% | |
7 | ||
8 | %%%----- Licensing notice --------------------------------------------------- | |
9 | %%% | |
e0808c47 | 10 | %%% This file is part of the Sensible Object Design, an object system for C. |
1f7d590d MW |
11 | %%% |
12 | %%% SOD is free software; you can redistribute it and/or modify | |
13 | %%% it under the terms of the GNU General Public License as published by | |
14 | %%% the Free Software Foundation; either version 2 of the License, or | |
15 | %%% (at your option) any later version. | |
16 | %%% | |
17 | %%% SOD is distributed in the hope that it will be useful, | |
18 | %%% but WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | %%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
20 | %%% GNU General Public License for more details. | |
21 | %%% | |
22 | %%% You should have received a copy of the GNU General Public License | |
23 | %%% along with SOD; if not, write to the Free Software Foundation, | |
24 | %%% Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
25 | ||
26 | \chapter{Module syntax} \label{ch:syntax} | |
27 | ||
28 | %%%-------------------------------------------------------------------------- | |
68a620ab | 29 | \section{Notation} \label{sec:syntax.notation} |
1f7d590d | 30 | |
0bc19f1c MW |
31 | Fortunately, Sod is syntactically quite simple. The notation is slightly |
32 | unusual in order to make the presentation shorter and easier to read. | |
33 | ||
34 | Anywhere a simple nonterminal name $x$ may appear in the grammar, an | |
35 | \emph{indexed} nonterminal $x[a_1, \ldots, a_n]$ may also appear. On the | |
36 | left-hand side of a production rule, the indices $a_1$, \ldots, $a_n$ are | |
37 | variables which vary over all nonterminal and terminal symbols, and the | |
38 | variables may also appear on the right-hand side in place of a nonterminal. | |
39 | Such a rule stands for a family of rules, in each variable is replaced by | |
40 | each possible simple nonterminal or terminal symbol. | |
41 | ||
42 | The letter $\epsilon$ denotes the empty nonterminal | |
43 | \begin{quote} | |
44 | \syntax{$\epsilon$ ::=} | |
45 | \end{quote} | |
46 | ||
47 | The following indexed productions are used throughout the grammar, some often | |
48 | enough that they deserve special notation. | |
1f7d590d | 49 | \begin{itemize} |
0bc19f1c MW |
50 | \item @[$x$@] abbreviates @<optional>$[x]$, denoting an optional occurrence |
51 | of $x$: | |
1f7d590d | 52 | \begin{quote} |
0bc19f1c | 53 | \syntax{@[$x$@] ::= <optional>$[x]$ ::= $\epsilon$ @! $x$} |
1f7d590d | 54 | \end{quote} |
0bc19f1c MW |
55 | \item $x^*$ abbreviates @<zero-or-more>$[x]$, denoting a sequence of zero or |
56 | more occurrences of $x$: | |
1f7d590d | 57 | \begin{quote} |
0bc19f1c MW |
58 | \syntax{$x^*$ ::= <zero-or-more>$[x]$ ::= |
59 | $\epsilon$ @! <zero-or-more>$[x]$ $x$} | |
1f7d590d | 60 | \end{quote} |
0bc19f1c MW |
61 | \item $x^+$ abbreviates @<one-or-more>$[x]$, denoting a sequence of zero or |
62 | more occurrences of $x$: | |
1f7d590d | 63 | \begin{quote} |
0bc19f1c | 64 | \syntax{$x^+$ ::= <one-or-more>$[x]$ ::= <zero-or-more>$[x]$ $x$} |
1f7d590d | 65 | \end{quote} |
0bc19f1c MW |
66 | \item @<list>$[x]$ denotes a sequence of one or more occurrences of $x$ |
67 | separated by commas: | |
1f7d590d | 68 | \begin{quote} |
0bc19f1c | 69 | \syntax{<list>$[x]$ ::= $x$ @! <list>$[x]$ "," $x$} |
1f7d590d MW |
70 | \end{quote} |
71 | \end{itemize} | |
72 | ||
68a620ab MW |
73 | %%%-------------------------------------------------------------------------- |
74 | \section{Lexical syntax} \label{sec:syntax.lex} | |
1f7d590d MW |
75 | |
76 | Whitespace and comments are discarded. The remaining characters are | |
77 | collected into tokens according to the following syntax. | |
78 | ||
79 | \begin{grammar} | |
80 | <token> ::= <identifier> | |
81 | \alt <string-literal> | |
82 | \alt <char-literal> | |
83 | \alt <integer-literal> | |
84 | \alt <punctuation> | |
85 | \end{grammar} | |
86 | ||
87 | This syntax is slightly ambiguous, and is disambiguated by the \emph{maximal | |
88 | munch} rule: at each stage we take the longest sequence of characters which | |
89 | could be a token. | |
90 | ||
68a620ab MW |
91 | |
92 | \subsection{Identifiers} \label{sec:syntax.lex.id} | |
1f7d590d MW |
93 | |
94 | \begin{grammar} | |
95 | <identifier> ::= <id-start-char> @<id-body-char>^* | |
96 | ||
97 | <id-start-char> ::= <alpha-char> | "_" | |
98 | ||
99 | <id-body-char> ::= <id-start-char> @! <digit-char> | |
100 | ||
101 | <alpha-char> ::= "A" | "B" | \dots\ | "Z" | |
102 | \alt "a" | "b" | \dots\ | "z" | |
103 | \alt <extended-alpha-char> | |
104 | ||
105 | <digit-char> ::= "0" | <nonzero-digit-char> | |
106 | ||
107 | <nonzero-digit-char> ::= "1" | "2" $| \cdots |$ "9" | |
108 | \end{grammar} | |
109 | ||
110 | The precise definition of @<alpha-char> is left to the function | |
111 | \textsf{alpha-char-p} in the hosting Lisp system. For portability, | |
112 | programmers are encouraged to limit themselves to the standard ASCII letters. | |
113 | ||
114 | There are no reserved words at the lexical level, but the higher-level syntax | |
115 | recognizes certain identifiers as \emph{keywords} in some contexts. There is | |
116 | also an ambiguity (inherited from C) in the declaration syntax which is | |
117 | settled by distinguishing type names from other identifiers at a lexical | |
118 | level. | |
119 | ||
68a620ab MW |
120 | |
121 | \subsection{String and character literals} \label{sec:syntax.lex.string} | |
1f7d590d MW |
122 | |
123 | \begin{grammar} | |
124 | <string-literal> ::= "\"" @<string-literal-char>^* "\"" | |
125 | ||
126 | <char-literal> ::= "'" <char-literal-char> "'" | |
127 | ||
128 | <string-literal-char> ::= any character other than "\\" or "\"" | |
129 | \alt "\\" <char> | |
130 | ||
131 | <char-literal-char> ::= any character other than "\\" or "'" | |
132 | \alt "\\" <char> | |
133 | ||
134 | <char> ::= any single character | |
135 | \end{grammar} | |
136 | ||
137 | The syntax for string and character literals differs from~C. In particular, | |
138 | escape sequences such as @`\textbackslash n' are not recognized. The use | |
139 | of string and character literals in Sod, outside of C~fragments, is limited, | |
140 | and the simple syntax seems adequate. For the sake of future compatibility, | |
141 | the use of character sequences which resemble C escape sequences is | |
142 | discouraged. | |
143 | ||
144 | \subsubsection{Integer literals} \label{sec:syntax.lex.int} | |
145 | ||
146 | \begin{grammar} | |
147 | <integer-literal> ::= <decimal-integer> | |
148 | \alt <binary-integer> | |
149 | \alt <octal-integer> | |
150 | \alt <hex-integer> | |
151 | ||
cc0bcf39 | 152 | <decimal-integer> ::= "0" | <nonzero-digit-char> @<digit-char>^* |
1f7d590d MW |
153 | |
154 | <binary-integer> ::= "0" @("b"|"B"@) @<binary-digit-char>^+ | |
155 | ||
156 | <binary-digit-char> ::= "0" | "1" | |
157 | ||
158 | <octal-integer> ::= "0" @["o"|"O"@] @<octal-digit-char>^+ | |
159 | ||
160 | <octal-digit-char> ::= "0" | "1" $| \cdots |$ "7" | |
161 | ||
162 | <hex-integer> ::= "0" @("x"|"X"@) @<hex-digit-char>^+ | |
163 | ||
164 | <hex-digit-char> ::= <digit-char> | |
165 | \alt "A" | "B" | "C" | "D" | "E" | "F" | |
166 | \alt "a" | "b" | "c" | "d" | "e" | "f" | |
167 | \end{grammar} | |
168 | ||
169 | Sod understands only integers, not floating-point numbers; its integer syntax | |
170 | goes slightly beyond C in allowing a @`0o' prefix for octal and @`0b' for | |
171 | binary. However, length and signedness indicators are not permitted. | |
172 | ||
68a620ab MW |
173 | |
174 | \subsection{Punctuation} \label{sec:syntax.lex.punct} | |
1f7d590d MW |
175 | |
176 | \begin{grammar} | |
177 | <punctuation> ::= any nonalphanumeric character other than "_", "\"" or "'" | |
178 | \end{grammar} | |
179 | ||
68a620ab MW |
180 | |
181 | \subsection{Comments} \label{sec:syntax.lex.comment} | |
1f7d590d MW |
182 | |
183 | \begin{grammar} | |
184 | <comment> ::= <block-comment> | |
185 | \alt <line-comment> | |
186 | ||
187 | <block-comment> ::= | |
188 | "/*" | |
189 | @<not-star>^* @(@<star>^+ <not-star-or-slash> @<not-star>^*@)^* | |
190 | @<star>^* | |
191 | "*/" | |
192 | ||
193 | <star> ::= "*" | |
194 | ||
195 | <not-star> ::= any character other than "*" | |
196 | ||
197 | <not-star-or-slash> ::= any character other than "*" or "/" | |
198 | ||
199 | <line-comment> ::= "//" @<not-newline>^* <newline> | |
200 | ||
201 | <newline> ::= a newline character | |
202 | ||
203 | <not-newline> ::= any character other than newline | |
204 | \end{grammar} | |
205 | ||
206 | Comments are exactly as in C99: both traditional block comments `\texttt{/*} | |
207 | \dots\ \texttt{*/}' and \Cplusplus-style `\texttt{//} \dots' comments are | |
208 | permitted and ignored. | |
209 | ||
68a620ab MW |
210 | |
211 | \subsection{Special nonterminals} \label{sec:syntax.lex.special} | |
1f7d590d MW |
212 | |
213 | Aside from the lexical syntax presented above (\xref{sec:lexical-syntax}), | |
214 | two special nonterminals occur in the module syntax. | |
215 | ||
68a620ab | 216 | \subsubsection{S-expressions} |
1f7d590d MW |
217 | \begin{grammar} |
218 | <s-expression> ::= an S-expression, as parsed by the Lisp reader | |
219 | \end{grammar} | |
220 | ||
221 | When an S-expression is expected, the Sod parser simply calls the host Lisp | |
68a620ab MW |
222 | system's @|read| function. Sod modules are permitted to modify the read |
223 | table to extend the S-expression syntax. | |
1f7d590d MW |
224 | |
225 | S-expressions are self-delimiting, so no end-marker is needed. | |
226 | ||
68a620ab | 227 | \subsubsection{C fragments} |
1f7d590d MW |
228 | \begin{grammar} |
229 | <c-fragment> ::= a sequence of C tokens, with matching brackets | |
230 | \end{grammar} | |
231 | ||
232 | Sequences of C code are simply stored and written to the output unchanged | |
233 | during translation. They are read using a simple scanner which nonetheless | |
234 | understands C comments and string and character literals. | |
235 | ||
236 | A C fragment is terminated by one of a small number of delimiter characters | |
237 | determined by the immediately surrounding context -- usually a closing brace | |
238 | or bracket. The first such delimiter character which is not enclosed in | |
239 | brackets, braces or parenthesis ends the fragment. | |
240 | ||
68a620ab MW |
241 | %%%-------------------------------------------------------------------------- |
242 | \section{Module syntax} \label{sec:syntax.module} | |
1f7d590d MW |
243 | |
244 | \begin{grammar} | |
245 | <module> ::= @<definition>^* | |
246 | ||
247 | <definition> ::= <import-definition> | |
248 | \alt <load-definition> | |
249 | \alt <lisp-definition> | |
250 | \alt <code-definition> | |
251 | \alt <typename-definition> | |
252 | \alt <class-definition> | |
253 | \end{grammar} | |
254 | ||
68a620ab MW |
255 | A @<module> is the top-level syntactic item. A module consists of a sequence |
256 | of definitions. | |
1f7d590d | 257 | |
68a620ab | 258 | \subsection{Simple definitions} \label{sec:syntax.module.simple} |
1f7d590d | 259 | |
68a620ab | 260 | \subsubsection{Importing modules} |
1f7d590d MW |
261 | \begin{grammar} |
262 | <import-definition> ::= "import" <string> ";" | |
263 | \end{grammar} | |
264 | ||
265 | The module named @<string> is processed and its definitions made available. | |
266 | ||
267 | A search is made for a module source file as follows. | |
268 | \begin{itemize} | |
269 | \item The module name @<string> is converted into a filename by appending | |
270 | @`.sod', if it has no extension already.\footnote{% | |
271 | Technically, what happens is \textsf{(merge-pathnames name (make-pathname | |
272 | :type "SOD" :case :common))}, so exactly what this means varies | |
273 | according to the host system.} % | |
274 | \item The file is looked for relative to the directory containing the | |
275 | importing module. | |
276 | \item If that fails, then the file is looked for in each directory on the | |
277 | module search path in turn. | |
278 | \item If the file still isn't found, an error is reported and the import | |
279 | fails. | |
280 | \end{itemize} | |
281 | At this point, if the file has previously been imported, nothing further | |
282 | happens.\footnote{% | |
283 | This check is done using \textsf{truename}, so it should see through simple | |
284 | tricks like symbolic links. However, it may be confused by fancy things | |
285 | like bind mounts and so on.} % | |
286 | ||
287 | Recursive imports, either direct or indirect, are an error. | |
288 | ||
68a620ab | 289 | \subsubsection{Loading extensions} |
1f7d590d MW |
290 | \begin{grammar} |
291 | <load-definition> ::= "load" <string> ";" | |
292 | \end{grammar} | |
293 | ||
294 | The Lisp file named @<string> is loaded and evaluated. | |
295 | ||
296 | A search is made for a Lisp source file as follows. | |
297 | \begin{itemize} | |
298 | \item The name @<string> is converted into a filename by appending @`.lisp', | |
299 | if it has no extension already.\footnote{% | |
300 | Technically, what happens is \textsf{(merge-pathnames name (make-pathname | |
301 | :type "LISP" :case :common))}, so exactly what this means varies | |
302 | according to the host system.} % | |
303 | \item A search is then made in the same manner as for module imports | |
304 | (\xref{sec:syntax-module}). | |
305 | \end{itemize} | |
306 | If the file is found, it is loaded using the host Lisp's \textsf{load} | |
307 | function. | |
308 | ||
309 | Note that Sod doesn't attempt to compile Lisp files, or even to look for | |
310 | existing compiled files. The right way to package a substantial extension to | |
311 | the Sod translator is to provide the extension as a standard ASDF system (or | |
312 | similar) and leave a dropping @"foo-extension.lisp" in the module path saying | |
313 | something like | |
314 | \begin{quote} | |
315 | \textsf{(asdf:load-system :foo-extension)} | |
316 | \end{quote} | |
317 | which will arrange for the extension to be compiled if necessary. | |
318 | ||
319 | (This approach means that the language doesn't need to depend on any | |
320 | particular system definition facility. It's bad enough already that it | |
321 | depends on Common Lisp.) | |
322 | ||
68a620ab | 323 | \subsubsection{Lisp escapes} |
1f7d590d MW |
324 | \begin{grammar} |
325 | <lisp-definition> ::= "lisp" <s-expression> ";" | |
326 | \end{grammar} | |
327 | ||
328 | The @<s-expression> is evaluated immediately. It can do anything it likes. | |
329 | ||
eae50115 MW |
330 | \begin{boxy}[Warning!] |
331 | This means that hostile Sod modules are a security hazard. Lisp code can | |
332 | read and write files, start other programs, and make network connections. | |
333 | Don't install Sod modules from sources that you don't trust.\footnote{% | |
334 | Presumably you were going to run the corresponding code at some point, so | |
335 | this isn't as unusually scary as it sounds. But please be careful.} % | |
336 | \end{boxy} | |
1f7d590d | 337 | |
68a620ab | 338 | \subsubsection{Declaring type names} |
1f7d590d MW |
339 | \begin{grammar} |
340 | <typename-definition> ::= | |
ea08dc56 | 341 | "typename" <list>$[\mbox{@<identifier>}]$ ";" |
1f7d590d MW |
342 | \end{grammar} |
343 | ||
344 | Each @<identifier> is declared as naming a C type. This is important because | |
345 | the C type syntax -- which Sod uses -- is ambiguous, and disambiguation is | |
346 | done by distinguishing type names from other identifiers. | |
347 | ||
348 | Don't declare class names using @"typename"; use @"class" forward | |
349 | declarations instead. | |
350 | ||
68a620ab MW |
351 | |
352 | \subsection{Literal code} \label{sec:syntax.module.literal} | |
1f7d590d MW |
353 | |
354 | \begin{grammar} | |
355 | <code-definition> ::= | |
4fc52153 | 356 | "code" <identifier> ":" <item-name> @[<constraints>@] |
1f7d590d MW |
357 | "{" <c-fragment> "}" |
358 | ||
ea08dc56 | 359 | <constraints> ::= "[" <list>$[\mbox{@<constraint>}]$ "]" |
1f7d590d | 360 | |
4fc52153 MW |
361 | <constraint> ::= @<item-name>^+ |
362 | ||
363 | <item-name> ::= <identifier> @! "(" @<identifier>^+ ")" | |
1f7d590d MW |
364 | \end{grammar} |
365 | ||
366 | The @<c-fragment> will be output unchanged to one of the output files. | |
367 | ||
368 | The first @<identifier> is the symbolic name of an output file. Predefined | |
369 | output file names are @"c" and @"h", which are the implementation code and | |
370 | header file respectively; other output files can be defined by extensions. | |
371 | ||
4fc52153 MW |
372 | Output items are named with a sequence of identifiers, separated by |
373 | whitespace, and enclosed in parentheses. As an abbreviation, a name | |
374 | consisting of a single identifier may be written as just that identifier, | |
375 | without the parentheses. | |
1f7d590d MW |
376 | |
377 | The @<constraints> provide a means for specifying where in the output file | |
378 | the output item should appear. (Note the two kinds of square brackets shown | |
379 | in the syntax: square brackets must appear around the constraints if they are | |
380 | present, but that they may be omitted.) Each comma-separated @<constraint> | |
4fc52153 MW |
381 | is a sequence of names of output items, and indicates that the output items |
382 | must appear in the order given -- though the translator is free to insert | |
383 | additional items in between them. (The particular output items needn't be | |
384 | defined already -- indeed, they needn't be defined ever.) | |
1f7d590d MW |
385 | |
386 | There is a predefined output item @"includes" in both the @"c" and @"h" | |
387 | output files which is a suitable place for inserting @"\#include" | |
388 | preprocessor directives in order to declare types and functions for use | |
389 | elsewhere in the generated output files. | |
390 | ||
1f7d590d | 391 | |
68a620ab | 392 | \subsection{Property sets} \label{sec:syntax.module.properties} |
1f7d590d | 393 | \begin{grammar} |
ea08dc56 | 394 | <properties> ::= "[" <list>$[\mbox{@<property>}]$ "]" |
1f7d590d MW |
395 | |
396 | <property> ::= <identifier> "=" <expression> | |
397 | \end{grammar} | |
398 | ||
399 | Property sets are a means for associating miscellaneous information with | |
400 | classes and related items. By using property sets, additional information | |
401 | can be passed to extensions without the need to introduce idiosyncratic | |
402 | syntax. | |
403 | ||
404 | A property has a name, given as an @<identifier>, and a value computed by | |
405 | evaluating an @<expression>. The value can be one of a number of types, | |
406 | though the only operators currently defined act on integer values only. | |
407 | ||
68a620ab | 408 | \subsubsection{The expression evaluator} |
1f7d590d MW |
409 | \begin{grammar} |
410 | <expression> ::= <term> | <expression> "+" <term> | <expression> "-" <term> | |
411 | ||
412 | <term> ::= <factor> | <term> "*" <factor> | <term> "/" <factor> | |
413 | ||
414 | <factor> ::= <primary> | "+" <factor> | "-" <factor> | |
415 | ||
416 | <primary> ::= | |
417 | <integer-literal> | <string-literal> | <char-literal> | <identifier> | |
418 | \alt "?" <s-expression> | |
419 | \alt "(" <expression> ")" | |
420 | \end{grammar} | |
421 | ||
422 | The arithmetic expression syntax is simple and standard; there are currently | |
423 | no bitwise, logical, or comparison operators. | |
424 | ||
425 | A @<primary> expression may be a literal or an identifier. Note that | |
426 | identifiers stand for themselves: they \emph{do not} denote values. For more | |
427 | fancy expressions, the syntax | |
428 | \begin{quote} | |
429 | @"?" @<s-expression> | |
430 | \end{quote} | |
431 | causes the @<s-expression> to be evaluated using the Lisp \textsf{eval} | |
432 | function. | |
433 | %%% FIXME crossref to extension docs | |
434 | ||
68a620ab MW |
435 | |
436 | \subsection{C types} \label{sec:syntax.module.types} | |
1f7d590d MW |
437 | |
438 | Sod's syntax for C types closely mirrors the standard C syntax. A C type has | |
439 | two parts: a sequence of @<declaration-specifier>s and a @<declarator>. In | |
440 | Sod, a type must contain at least one @<declaration-specifier> (i.e., | |
441 | `implicit @"int"' is forbidden), and storage-class specifiers are not | |
442 | recognized. | |
443 | ||
68a620ab | 444 | \subsubsection{Declaration specifiers} |
1f7d590d MW |
445 | \begin{grammar} |
446 | <declaration-specifier> ::= <type-name> | |
447 | \alt "struct" <identifier> | "union" <identifier> | "enum" <identifier> | |
448 | \alt "void" | "char" | "int" | "float" | "double" | |
449 | \alt "short" | "long" | |
450 | \alt "signed" | "unsigned" | |
2e01fd8b MW |
451 | \alt "bool" | "_Bool" |
452 | \alt "imaginary" | "_Imaginary" | "complex" | "_Complex" | |
1f7d590d | 453 | \alt <qualifier> |
ae0f15ee | 454 | \alt <atomic-type> |
1f7d590d | 455 | |
ae0f15ee MW |
456 | <qualifier> ::= <atomic> | "const" | "volatile" | "restrict" |
457 | ||
458 | <atomic-type> ::= | |
459 | <atomic> "(" @<declaration-specifier>^+ <abstract-declarator> ")" | |
460 | ||
461 | <atomic> ::= "atomic" | "_Atomic" | |
1f7d590d MW |
462 | |
463 | <type-name> ::= <identifier> | |
464 | \end{grammar} | |
465 | ||
466 | A @<type-name> is an identifier which has been declared as being a type name, | |
2e01fd8b MW |
467 | using the @"typename" or @"class" definitions. The following type names are |
468 | defined in the built-in module. | |
469 | \begin{itemize} | |
470 | \item @"va_list" | |
471 | \item @"size_t" | |
472 | \item @"ptrdiff_t" | |
473 | \item @"wchar_t" | |
474 | \end{itemize} | |
1f7d590d MW |
475 | |
476 | Declaration specifiers may appear in any order. However, not all | |
477 | combinations are permitted. A declaration specifier must consist of zero or | |
c32aa709 | 478 | more @<qualifier>s, and one of the following, up to reordering. |
1f7d590d MW |
479 | \begin{itemize} |
480 | \item @<type-name> | |
ae0f15ee | 481 | \item @<atomic-type> |
1f7d590d MW |
482 | \item @"struct" @<identifier>, @"union" @<identifier>, @"enum" @<identifier> |
483 | \item @"void" | |
2e01fd8b | 484 | \item @"_Bool", @"bool" |
1f7d590d MW |
485 | \item @"char", @"unsigned char", @"signed char" |
486 | \item @"short", @"unsigned short", @"signed short" | |
487 | \item @"short int", @"unsigned short int", @"signed short int" | |
488 | \item @"int", @"unsigned int", @"signed int", @"unsigned", @"signed" | |
489 | \item @"long", @"unsigned long", @"signed long" | |
490 | \item @"long int", @"unsigned long int", @"signed long int" | |
491 | \item @"long long", @"unsigned long long", @"signed long long" | |
492 | \item @"long long int", @"unsigned long long int", @"signed long long int" | |
493 | \item @"float", @"double", @"long double" | |
2e01fd8b MW |
494 | \item @"float _Imaginary", @"double _Imaginary", @"long double _Imaginary" |
495 | \item @"float imaginary", @"double imaginary", @"long double imaginary" | |
496 | \item @"float _Complex", @"double _Complex", @"long double _Complex" | |
497 | \item @"float complex", @"double complex", @"long double complex" | |
1f7d590d MW |
498 | \end{itemize} |
499 | All of these have their usual C meanings. | |
500 | ||
68a620ab | 501 | \subsubsection{Declarators} |
1f7d590d MW |
502 | \begin{grammar} |
503 | <declarator>$[k]$ ::= @<pointer>^* <primary-declarator>$[k]$ | |
504 | ||
505 | <primary-declarator>$[k]$ ::= $k$ | |
506 | \alt "(" <primary-declarator>$[k]$ ")" | |
0a488b1c | 507 | \alt <primary-declarator>$[k]$ @<declarator-suffix> |
1f7d590d MW |
508 | |
509 | <pointer> ::= "*" @<qualifier>^* | |
510 | ||
511 | <declarator-suffix> ::= "[" <c-fragment> "]" | |
512 | \alt "(" <arguments> ")" | |
513 | ||
ea08dc56 MW |
514 | <argument-list> ::= $\epsilon$ | "..." |
515 | \alt <list>$[\mbox{@<argument>}]$ @["," "..."@] | |
1f7d590d MW |
516 | |
517 | <argument> ::= @<declaration-specifier>^+ <argument-declarator> | |
518 | ||
ae0f15ee MW |
519 | <abstract-declarator> ::= <declarator>$[\epsilon]$ |
520 | ||
ea08dc56 | 521 | <argument-declarator> ::= <declarator>$[\mbox{@<identifier> @! $\epsilon$}]$ |
1f7d590d | 522 | |
ea08dc56 | 523 | <simple-declarator> ::= <declarator>$[\mbox{@<identifier>}]$ |
1f7d590d MW |
524 | |
525 | <dotted-name> ::= <identifier> "." <identifier> | |
1f7d590d MW |
526 | \end{grammar} |
527 | ||
528 | The declarator syntax is taken from C, but with some differences. | |
529 | \begin{itemize} | |
530 | \item Array dimensions are uninterpreted @<c-fragments>, terminated by a | |
531 | closing square bracket. This allows array dimensions to contain arbitrary | |
532 | constant expressions. | |
533 | \item A declarator may have either a single @<identifier> at its centre or a | |
534 | pair of @<identifier>s separated by a @`.'; this is used to refer to | |
535 | slots or messages defined in superclasses. | |
536 | \end{itemize} | |
537 | The remaining differences are (I hope) a matter of presentation rather than | |
538 | substance. | |
539 | ||
68a620ab MW |
540 | |
541 | \subsection{Class definitions} \label{sec:syntax.module.class} | |
1f7d590d MW |
542 | |
543 | \begin{grammar} | |
544 | <class-definition> ::= <class-forward-declaration> | |
545 | \alt <full-class-definition> | |
546 | \end{grammar} | |
547 | ||
68a620ab | 548 | \subsubsection{Forward declarations} |
1f7d590d MW |
549 | \begin{grammar} |
550 | <class-forward-declaration> ::= "class" <identifier> ";" | |
551 | \end{grammar} | |
552 | ||
553 | A @<class-forward-declaration> informs Sod that an @<identifier> will be used | |
554 | to name a class which is currently undefined. Forward declarations are | |
555 | necessary in order to resolve certain kinds of circularity. For example, | |
556 | \begin{listing} | |
557 | class Sub; | |
558 | ||
559 | class Super : SodObject { | |
560 | Sub *sub; | |
561 | }; | |
562 | ||
563 | class Sub : Super { | |
564 | /* ... */ | |
565 | }; | |
566 | \end{listing} | |
567 | ||
68a620ab | 568 | \subsubsection{Full class definitions} |
1f7d590d MW |
569 | \begin{grammar} |
570 | <full-class-definition> ::= | |
571 | @[<properties>@] | |
ea08dc56 MW |
572 | "class" <identifier> ":" <list>$[\mbox{@<identifier>}]$ |
573 | "{" @<properties-class-item>^* "}" | |
1f7d590d | 574 | |
391c5a34 MW |
575 | <properties-class-item> ::= @[<properties>@] <class-item> |
576 | ||
577 | <class-item> ::= <slot-item> | |
578 | \alt <initializer-item> | |
1f7d590d MW |
579 | \alt <message-item> |
580 | \alt <method-item> | |
1f7d590d MW |
581 | \end{grammar} |
582 | ||
583 | A full class definition provides a complete description of a class. | |
584 | ||
585 | The first @<identifier> gives the name of the class. It is an error to | |
586 | give the name of an existing class (other than a forward-referenced class), | |
587 | or an existing type name. It is conventional to give classes `MixedCase' | |
588 | names, to distinguish them from other kinds of identifiers. | |
589 | ||
ea08dc56 MW |
590 | The @<list>$[\mbox{@<identifier>}]$ names the direct superclasses for the new |
591 | class. It is an error if any of these @<identifier>s does not name a defined | |
592 | class. | |
1f7d590d MW |
593 | |
594 | The @<properties> provide additional information. The standard class | |
595 | properties are as follows. | |
596 | \begin{description} | |
597 | \item[@"lisp_class"] The name of the Lisp class to use within the translator | |
598 | to represent this class. The property value must be an identifier; the | |
599 | default is @"sod_class". Extensions may define classes with additional | |
600 | behaviour, and may recognize additional class properties. | |
601 | \item[@"metaclass"] The name of the Sod metaclass for this class. In the | |
602 | generated code, a class is itself an instance of another class -- its | |
603 | \emph{metaclass}. The metaclass defines which slots the class will have, | |
604 | which messages it will respond to, and what its behaviour will be when it | |
605 | receives them. The property value must be an identifier naming a defined | |
606 | subclass of @"SodClass". The default metaclass is @"SodClass". | |
607 | %%% FIXME xref to theory | |
608 | \item[@"nick"] A nickname for the class, to be used to distinguish it from | |
609 | other classes in various limited contexts. The property value must be an | |
610 | identifier; the default is constructed by forcing the class name to | |
611 | lower-case. | |
612 | \end{description} | |
613 | ||
614 | The class body consists of a sequence of @<class-item>s enclosed in braces. | |
615 | These items are discussed on the following sections. | |
616 | ||
68a620ab | 617 | \subsubsection{Slot items} |
1f7d590d MW |
618 | \begin{grammar} |
619 | <slot-item> ::= | |
ea08dc56 | 620 | @<declaration-specifier>^+ <list>$[\mbox{@<init-declarator>}]$ ";" |
1f7d590d | 621 | |
0bc19f1c | 622 | <init-declarator> ::= <simple-declarator> @["=" <initializer>@] |
1f7d590d MW |
623 | \end{grammar} |
624 | ||
625 | A @<slot-item> defines one or more slots. All instances of the class and any | |
626 | subclass will contain these slot, with the names and types given by the | |
627 | @<declaration-specifiers> and the @<declarators>. Slot declarators may not | |
bc7dff5c | 628 | contain dotted names. |
1f7d590d MW |
629 | |
630 | It is not possible to declare a slot with function type: such an item is | |
631 | interpreted as being a @<message-item> or @<method-item>. Pointers to | |
632 | functions are fine. | |
633 | ||
634 | An @<initializer>, if present, is treated as if a separate | |
635 | @<initializer-item> containing the slot name and initializer were present. | |
636 | For example, | |
637 | \begin{listing} | |
638 | [nick = eg] | |
639 | class Example : Super { | |
640 | int foo = 17; | |
641 | }; | |
642 | \end{listing} | |
643 | means the same as | |
644 | \begin{listing} | |
645 | [nick = eg] | |
646 | class Example : Super { | |
647 | int foo; | |
648 | eg.foo = 17; | |
649 | }; | |
650 | \end{listing} | |
651 | ||
68a620ab | 652 | \subsubsection{Initializer items} |
1f7d590d | 653 | \begin{grammar} |
391c5a34 | 654 | <initializer-item> ::= @["class"@] <list>$[\mbox{@<slot-initializer>}]$ ";" |
1f7d590d | 655 | |
bc7dff5c | 656 | <slot-initializer> ::= <dotted-name> "=" <initializer> |
1f7d590d MW |
657 | |
658 | <initializer> :: "{" <c-fragment> "}" | <c-fragment> | |
659 | \end{grammar} | |
660 | ||
661 | An @<initializer-item> provides an initial value for one or more slots. If | |
662 | prefixed by @"class", then the initial values are for class slots (i.e., | |
663 | slots of the class object itself); otherwise they are for instance slots. | |
664 | ||
bc7dff5c MW |
665 | The first component of the @<dotted-name> must be the nickname of one of the |
666 | class's superclasses (including itself); the second must be the name of a | |
667 | slot defined in that superclass. | |
1f7d590d MW |
668 | |
669 | The initializer has one of two forms. | |
670 | \begin{itemize} | |
671 | \item A @<c-fragment> enclosed in braces denotes an aggregate initializer. | |
672 | This is suitable for initializing structure, union or array slots. | |
673 | \item A @<c-fragment> \emph{not} beginning with an open brace is a `bare' | |
674 | initializer, and continues until the next @`,' or @`;' which is not within | |
675 | nested brackets. Bare initializers are suitable for initializing scalar | |
676 | slots, such as pointers or integers, and strings. | |
677 | \end{itemize} | |
678 | ||
68a620ab | 679 | \subsubsection{Message items} |
1f7d590d MW |
680 | \begin{grammar} |
681 | <message-item> ::= | |
391c5a34 MW |
682 | @<declaration-specifier>^+ |
683 | <keyword-declarator>$[\mbox{@<identifier>}]$ | |
684 | @[<method-body>@] | |
1f7d590d MW |
685 | \end{grammar} |
686 | ||
68a620ab | 687 | \subsubsection{Method items} |
1f7d590d MW |
688 | \begin{grammar} |
689 | <method-item> ::= | |
391c5a34 MW |
690 | @<declaration-specifier>^+ |
691 | <keyword-declarator>$[\mbox{@<dotted-name>}]$ | |
ea08dc56 | 692 | <method-body> |
1f7d590d MW |
693 | |
694 | <method-body> ::= "{" <c-fragment> "}" | "extern" ";" | |
695 | \end{grammar} | |
696 | ||
1f7d590d MW |
697 | %%%----- That's all, folks -------------------------------------------------- |
698 | ||
699 | %%% Local variables: | |
700 | %%% mode: LaTeX | |
701 | %%% TeX-master: "sod.tex" | |
702 | %%% TeX-PDF-mode: t | |
703 | %%% End: |