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d: make enum SymbolKind idiomatic D

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Taking into account comments from H. S. Teoh.
https://lists.gnu.org/r/bison-patches/2020-09/msg00021.html

* data/skeletons/d.m4, data/skeletons/lalr1.d (SymbolKind): Wrap the
enum in a structure that contains its string representation.
This commit is contained in:
Adela Vais
2020-09-11 15:53:45 +03:00
committed by Akim Demaille
parent b5e6d9c4ca
commit 2bc886dc02
3 changed files with 71 additions and 142 deletions
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84
TODO
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@@ -242,90 +242,6 @@ are. Keep the same variable names. If you change the wording in one place,
do it in the others too. In other words: make sure to keep the
maintenance *simple* by avoiding any gratuitous difference.
** Rename the D example
Move the current content of examples/d into examples/d/simple.
** Create a second example
Duplicate examples/d/simple into examples/d/calc.
** Add location tracking to d/calc
Look at the examples in the other languages to see how to do that.
** yysymbol_name
The SymbolKind is an enum. For a given SymbolKind we want to get its string
representation. Currently it's a separate table in the parser that does
that:
/* Symbol kinds. */
public enum SymbolKind
{
S_YYEMPTY = -2, /* No symbol. */
S_YYEOF = 0, /* "end of file" */
S_YYerror = 1, /* error */
S_YYUNDEF = 2, /* "invalid token" */
S_EQ = 3, /* "=" */
...
S_input = 14, /* input */
S_line = 15, /* line */
S_exp = 16, /* exp */
};
...
/* YYTNAME[SYMBOL-NUM] -- String name of the symbol SYMBOL-NUM.
First, the terminals, then, starting at \a yyntokens_, nonterminals. */
private static immutable string[] yytname_ =
[
"\"end of file\"", "error", "\"invalid token\"", "\"=\"", "\"+\"",
"\"-\"", "\"*\"", "\"/\"", "\"(\"", "\")\"", "\"end of line\"",
"\"number\"", "UNARY", "$accept", "input", "line", "exp", null
];
...
So to get a symbol kind, one runs `yytname_[yykind]`.
Is there a way to attach this conversion to string to SymbolKind? In Java
for instance, we have:
public enum SymbolKind
{
S_YYEOF(0), /* "end of file" */
S_YYerror(1), /* error */
S_YYUNDEF(2), /* "invalid token" */
...
S_input(16), /* input */
S_line(17), /* line */
S_exp(18); /* exp */
private final int yycode_;
SymbolKind (int n) {
this.yycode_ = n;
}
...
/* YYNAMES_[SYMBOL-NUM] -- String name of the symbol SYMBOL-NUM.
First, the terminals, then, starting at \a YYNTOKENS_, nonterminals. */
private static final String[] yynames_ = yynames_init();
private static final String[] yynames_init()
{
return new String[]
{
i18n("end of file"), i18n("error"), i18n("invalid token"), "!", "+", "-", "*",
"/", "^", "(", ")", "=", i18n("end of line"), i18n("number"), "NEG",
"$accept", "input", "line", "exp", null
};
}
/* The user-facing name of this symbol. */
public final String getName() {
return yynames_[yycode_];
}
};
which allows to write more naturally `yykind.getName()` rather than
`yytname_[yykind]`. Is there something comparable in (idiomatic) D?
** Change the return value of yylex
Historically people were allowed to return any int from the scanner (which
is convenient and allows `return '+'` from the scanner). Akim tends to see