examples: include the generated header

* examples/c/bistromathic/parse.y, examples/c/lexcalc/parse.y,
* examples/c/reccalc/parse.y: here.
Add some comments.

* src/parse-gram.y (api_version): Pull out of handle_require.
Bump to 3.7.

examples/c/bistromathic/parse.y

@@ -1,5 +1,6 @@
-%require "3.6"
+%require "3.7"
 
+// Emitted on top of the implementation file.
 %code top {
   #include <ctype.h>  // isdigit
   #include <locale.h> // LC_ALL
@@ -24,6 +25,7 @@
   #endif
 }
 
+// Emitted in the header file, before the definition of YYSTYPE.
 %code requires {
   // Function type.
   typedef double (func_t) (double);
@@ -46,6 +48,7 @@
   symrec *getsym (char const *name);
 }
 
+// Emitted in the header file, after the definition of YYSTYPE.
 %code provides {
 # ifndef __attribute__
 #  ifndef __GNUC__
@@ -57,6 +60,7 @@
     __attribute__ ((__format__ (__printf__, 2, 3)));
 }
 
+// Emitted in the implementation file.
 %code {
   #if defined ENABLE_NLS && ENABLE_NLS
   # define _(Msgid)  gettext (Msgid)
@@ -68,6 +72,9 @@
   int done = 0;
 }
 
+// Include the header in the implementation rather than duplicating it.
+%define api.header.include {"parse.h"}
+
 // Don't share global variables between the scanner and the parser.
 %define api.pure full
 

examples/c/lexcalc/parse.y

@@ -19,6 +19,9 @@
 #include <stdlib.h> // getenv.
 }
 
+// Include the header in the implementation rather than duplicating it.
+%define api.header.include {"parse.h"}
+
 // Don't share global variables between the scanner and the parser.
 %define api.pure full
 

examples/c/reccalc/parse.y

@@ -46,14 +46,29 @@
   result parse (void);
 }
 
+// Include the header in the implementation rather than duplicating it.
+%define api.header.include {"parse.h"}
+
+// Don't share global variables between the scanner and the parser.
 %define api.pure full
+
+// To avoid name clashes (e.g., with C's EOF) prefix token definitions
+// with TOK_ (e.g., TOK_EOF).
 %define api.token.prefix {TOK_}
+
+// Generate YYSTYPE from the types assigned to symbols.
 %define api.value.type union
-%define parse.error verbose
+
+// Error messages with "unexpected XXX, expected XXX...".
+%define parse.error detailed
+
+// Enable run-time traces (yydebug).
 %define parse.trace
+
+// Generate the parser description file (parse.output).
 %verbose
 
- // Scanner and error count are exchanged between main, yyparse and yylex.
+// Scanner and error count are exchanged between main, yyparse and yylex.
 %param {yyscan_t scanner}{result *res}
 
 %token

src/parse-gram.y

@@ -58,6 +58,10 @@
   #include "scan-code.h"
   #include "scan-gram.h"
 
+  /* Pretend to be at least that version, to check features published
+     in that version while developping it.  */
+  static const char* api_version = "3.7";
+
   static int current_prec = 0;
   static location current_lhs_loc;
   static named_ref *current_lhs_named_ref;
@@ -1082,9 +1086,6 @@ handle_require (location const *loc, char const *version_quoted)
     }
   else
     {
-      /* Pretend to be at least that version, to check features published
-         in that version while developping it.  */
-      const char* api_version = "3.6";
       const char* package_version =
         0 < strverscmp (api_version, PACKAGE_VERSION)
         ? api_version : PACKAGE_VERSION;