Change name and usage of presym macros

To be also able to build mruby without presym in the future. However,
`MRB_QSYM` has been removed and changed as follows:

### Example

|       Type                | Symbol |  Previous Style  |   New Style    |
|---------------------------|--------|------------------|----------------|
| Operator                  | &      | MRB_QSYM(and)    | MRB_OPSYM(and) |
| Class Variable            | @@foo  | MRB_QSYM(00_foo) | MRB_CVSYM(foo) |
| Instance Variable         | @foo   | MRB_QSYM(0_foo)  | MRB_IVSYM(foo) |
| Method with Bang          | foo!   | MRB_QSYM(foo_b)  | MRB_SYM_B(foo) |
| Method with Question mark | foo?   | MRB_QSYM(foo_p)  | MRB_SYM_Q(foo) |
| Mmethod with Equal        | foo=   | MRB_QSYM(foo_e)  | MRB_SYM_E(foo) |

This change makes it possible to define, for example, `MRB_IVSYM(foo)` as
`mrb_intern_lit(mrb, "@" "foo")`, which is useful if we support building
without presym in the future.

2 files changed, 30 insertions, 10 deletions

diff --git a/include/mruby.h b/include/mruby.h
index 6d03ba79c..0fad0d440 100644
--- a/include/mruby.h
+++ b/include/mruby.h
@@ -1080,7 +1080,8 @@ MRB_API mrb_value mrb_funcall_argv(mrb_state *mrb, mrb_value val, mrb_sym name,
  */
 MRB_API mrb_value mrb_funcall_with_block(mrb_state *mrb, mrb_value val, mrb_sym name, mrb_int argc, const mrb_value *argv, mrb_value block);
 /**
- * Create a symbol from C string. But usually it's better to use MRB_SYM(sym) and MRB_QSYM(qsym).
+ * Create a symbol from C string. But usually it's better to use MRB_SYM,
+ * MRB_OPSYM, MRB_CVSYM, MRB_IVSYM, MRB_SYM_B, MRB_SYM_Q, MRB_SYM_E macros.
  *
  * Example:
  *
@@ -1090,7 +1091,7 @@ MRB_API mrb_value mrb_funcall_with_block(mrb_state *mrb, mrb_value val, mrb_sym
  *     // C style:
  *     mrb_sym sym1 = mrb_intern_lit(mrb, "pizza"); //  => :pizza
  *     mrb_sym sym2 = MRB_SYM(pizza);               //  => :pizza
- *     mrb_sym sym3 = MRB_SYM(pizza_p);             //  => :pizza?
+ *     mrb_sym sym3 = MRB_SYM_Q(pizza);             //  => :pizza?
  *
  * @param mrb The current mruby state.
  * @param str The string to be symbolized
diff --git a/include/mruby/presym.h b/include/mruby/presym.h
index 3cc12e8fb..61e5bc8cb 100644
--- a/include/mruby/presym.h
+++ b/include/mruby/presym.h
@@ -8,18 +8,37 @@
 #define MRUBY_PRESYM_H
 
 #undef MRB_PRESYM_MAX
-#define MRB_PRESYM_CSYM(sym, num) MRB_PRESYM__##sym = (num<<1),
-#define MRB_PRESYM_QSYM(str, sym, num) MRB_PRESYM_q_##sym = (num<<1),
-#define MRB_PRESYM_SYM(sym, num) 
+#define MRB_PRESYM_NAMED(lit, num, type, name) MRB_##type##__##name = (num<<1),
+#define MRB_PRESYM_UNNAMED(lit, num)
 
 enum mruby_presym {
 #include <../build/presym.inc>
 };
 
-#undef MRB_PRESYM_CSYM
-#undef MRB_PRESYM_QSYM
-#undef MRB_PRESYM_SYM
+#undef MRB_PRESYM_NAMED
+#undef MRB_PRESYM_UNNAMED
+
+/*
+ * For `MRB_OPSYM`, specify the names corresponding to operators (refer to
+ * `op_table` in `Rakefile` for the names that can be specified for it).
+ * Other than that, describe only word characters excluding leading and
+ * ending punctuations.
+ *
+ * Example:
+ *   MRB_OPSYM(and)  //=> &
+ *   MRB_CVSYM(foo)  //=> @@foo
+ *   MRB_IVSYM(foo)  //=> @foo
+ *   MRB_SYM_B(foo)  //=> foo!
+ *   MRB_SYM_Q(foo)  //=> foo?
+ *   MRB_SYM_E(foo)  //=> foo=
+ *   MRB_SYM(foo)    //=> foo
+ */
+#define MRB_OPSYM(name) MRB_OPSYM__##name  /* Operator */
+#define MRB_CVSYM(name) MRB_CVSYM__##name  /* Class Variable */
+#define MRB_IVSYM(name) MRB_IVSYM__##name  /* Instance Variable */
+#define MRB_SYM_B(name) MRB_SYM_B__##name  /* Method with Bang */
+#define MRB_SYM_Q(name) MRB_SYM_Q__##name  /* Method with Question mark */
+#define MRB_SYM_E(name) MRB_SYM_E__##name  /* Method with Equal */
+#define MRB_SYM(name)   MRB_SYM__##name    /* Word characters */
 
-#define MRB_SYM(sym) MRB_PRESYM__##sym
-#define MRB_QSYM(sym) MRB_PRESYM_q_##sym
 #endif  /* MRUBY_PRESYM_H */