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TODO: update
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73
TODO
73
TODO
@@ -175,6 +175,9 @@ tremendously other languages such as D and Java that probably have no
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similar feature. If we remove jumps, we probably no longer need _Noreturn,
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so simplify `b4_attribute_define([noreturn])` into `b4_attribute_define`.
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After discussing with Valentin, it was decided that it's better to stay with
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jumps, since in some places exceptions are ruled out from C++.
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*** Coding style
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Move to our coding conventions. In particular names such as yy_glr_stack,
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not yyGLRStack.
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@@ -266,52 +269,8 @@ maintenance *simple* by avoiding any gratuitous difference.
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** CI
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Check when gdc and ldc.
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** Documentation
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Write documentation about D support in doc/bison.texi. Imitate the Java
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documentation. You should be more succinct IMHO.
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** yyerrok
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It appears that neither Java nor D support yyerrok currently. It does not
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need to be named this way...
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** Complete Symbols
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The current interface from the scanner to the parser is somewhat clumsy: the
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token kind is returned by yylex, but the value and location are stored in
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the scanner. This reflects the fact that the implementation of the parser
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uses three variables to deal with each parsed symbol: its kind, its value,
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its location.
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So today the scanner of examples/d/calc.d (no locations) looks like:
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if (input.front.isNumber)
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{
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import std.conv : parse;
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semanticVal_.ival = input.parse!int;
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return TokenKind.NUM;
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}
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and the generated parser:
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/* Read a lookahead token. */
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if (yychar == TokenKind.YYEMPTY)
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{
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yychar = yylex ();
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yylval = yylexer.semanticVal;
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}
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The parser class should feature a `Symbol` type which binds together kind,
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value and location, and the scanner should be able to return an instance of
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that type. Something like
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if (input.front.isNumber)
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{
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import std.conv : parse;
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return parser.Symbol (TokenKind.NUM, input.parse!int);
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}
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** Token Constructors
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In the previous example it is possible to mix incorrectly kinds and values,
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and for instance:
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It is possible to mix incorrectly kinds and values, and for instance:
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return parser.Symbol (TokenKind.NUM, "Hello, World!\n");
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@@ -324,10 +283,6 @@ example becomes
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which would easily be caught by the type checker.
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** Lookahead Correction
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Add support for LAC to the D skeleton. It should not be too hard: look how
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this is done in lalr1.cc, and mock it.
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** Push Parser
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Add support for push parser. Do not start a nice skeleton, just enhance the
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current one to support push parsers. This is going to be a tougher nut to
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@@ -449,7 +404,6 @@ define it to the same type as the C ptrdiff_t type.
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* Completion
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Several features are not available in all the back-ends.
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- lac: D, Java (easy)
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- push parsers: glr.c, glr.cc, lalr1.cc (not very difficult)
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- token constructors: Java, C, D (a bit difficult)
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- glr: D, Java (super difficult)
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@@ -584,23 +538,6 @@ It would be a very nice source of inspiration for the other languages.
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Valentin Tolmer is working on this.
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** yychar == YYEMPTY
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The code in yyerrlab reads:
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if (yychar <= YYEOF)
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{
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/* Return failure if at end of input. */
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if (yychar == YYEOF)
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YYABORT;
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}
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There are only two yychar that can be <= YYEOF: YYEMPTY and YYEOF.
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But I can't produce the situation where yychar is YYEMPTY here, is it
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really possible? The test suite does not exercise this case.
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This shows that it would be interesting to manage to install skeleton
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coverage analysis to the test suite.
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* From lalr1.cc to yacc.c
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** Single stack
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Merging the three stacks in lalr1.cc simplified the code, prompted for
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@@ -703,7 +640,7 @@ them together, paying attention to keep separate bits separated, in pseudo
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name spaces.
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** Push parsers
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There is demand for push parsers in Java and C++. And GLR I guess.
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There is demand for push parsers in C++.
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** Generate code instead of tables
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This is certainly quite a lot of work. See
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