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10.2.2 Class related Symbols

Here's an example which illustrates some C++ class syntactic symbols:

      1: class Bass
      2:     : public Guitar,
      3:       public Amplifiable
      4: {
      5: public:
      6:     Bass()
      7:         : eString( new BassString( 0.105 )),
      8:           aString( new BassString( 0.085 )),
      9:           dString( new BassString( 0.065 )),
     10:           gString( new BassString( 0.045 ))
     11:     {
     12:         eString.tune( 'E' );
     13:         aString.tune( 'A' );
     14:         dString.tune( 'D' );
     15:         gString.tune( 'G' );
     16:     }
     17:     friend class Luthier;
     18: };

As in the previous example, line 1 has the topmost-intro syntax. Here however, the brace that opens a C++ class definition on line 4 is assigned the class-open syntax. Note that in C++, classes, structs, and unions are essentially equivalent syntactically (and are very similar semantically), so replacing the class keyword in the example above with struct or union would still result in a syntax of class-open for line 4 1. Similarly, line 18 is assigned class-close syntax.

Line 2 introduces the inheritance list for the class so it is assigned the inher-intro syntax, and line 3, which continues the inheritance list is given inher-cont syntax.

Hitting C-c C-s on line 5 shows the following analysis:

     ((inclass 58) (access-label 58))

The primary syntactic symbol for this line is access-label as this is a label keyword that specifies access protection in C++. However, because this line is also a top-level construct inside a class definition, the analysis actually shows two syntactic symbols. The other syntactic symbol assigned to this line is inclass. Similarly, line 6 is given both inclass and topmost-intro syntax:

     ((inclass 58) (topmost-intro 60))

Line 7 introduces a C++ member initialization list and as such is given member-init-intro syntax. Note that in this case it is not assigned inclass since this is not considered a top-level construct. Lines 8 through 10 are all assigned member-init-cont since they continue the member initialization list started on line 7.

Line 11's analysis is a bit more complicated:

     ((inclass 58) (inline-open))

This line is assigned a syntax of both inline-open and inclass because it opens an in-class C++ inline method definition. This is distinct from, but related to, the C++ notion of an inline function in that its definition occurs inside an enclosing class definition, which in C++ implies that the function should be inlined. However, if the definition of the Bass constructor appeared outside the class definition, the construct would be given the defun-open syntax, even if the keyword inline appeared before the method name, as in:

      1: class Bass
      2:     : public Guitar,
      3:       public Amplifiable
      4: {
      5: public:
      6:     Bass();
      7: };
      9: inline
     10: Bass::Bass()
     11:     : eString( new BassString( 0.105 )),
     12:       aString( new BassString( 0.085 )),
     13:       dString( new BassString( 0.065 )),
     14:       gString( new BassString( 0.045 ))
     15: {
     16:     eString.tune( 'E' );
     17:     aString.tune( 'A' );
     18:     dString.tune( 'D' );
     19:     gString.tune( 'G' );
     20: }

Returning to the previous example, line 16 is given inline-close syntax, while line 12 is given defun-block-open syntax, and lines 13 through 15 are all given statement syntax. Line 17 is interesting in that its syntactic analysis list contains three elements:

     ((inclass 58) (topmost-intro 380) (friend))

The friend and inline-open syntactic symbols are modifiers that do not have anchor positions.

Template definitions introduce yet another syntactic symbol:

      1: ThingManager <int,
      2:    Framework::Callback *,
      3:    Mutex> framework_callbacks;

Here, line 1 is analyzed as a topmost-intro, but lines 2 and 3 are both analyzed as template-args-cont lines.


[1] This is the case even for C and Objective-C. For consistency, structs in all supported languages are syntactically equivalent to classes. Note however that the keyword class is meaningless in C and Objective-C.