Copyright (C) 2016-2017 Josua Groeger. groegerj at thp.uni-koeln dot de
YCLASS is an extension of the C programming language with object oriented elements, mostly by means of the C preprocessor.
YCLASS is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
YCLASS is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with YCLASS. If not, see http://www.gnu.org/licenses/.
While C itself is not an object oriented programming language, it can be used as such. This can be done by utilising structs and functions in a way that models classes and functions, i.e. to use C in its original form but use the existing language elements in a specific form. Another possibility is to make up some new syntax that is translated to C by some preprocessor. The first version (or predecessor) of C++ was implemented that way.
The objective of YCLASS is to have object oriented C by means of C's preprocessor, by inclusion of a single header file. I have read somewhere that the preprocessor is not meant to introduce new language elements. But this is exactly what YCLASS does.
Advantages and status:
- Easy to use.
- No additional software needed besides a C compiler.
- Lightweight.
- Everything seems to work now (classes, constructors, destructors, inheritance, virtual methods, signals and events, exceptions).
- Besides the disadvantages (see below), there are no known bugs.
Disadvantages and suggestions for improvement:
- Usage of the C preprocessor restricts the possibilities and does not prevent the user from using YCLASS in a way that is not intended.
- Compiler errors become really hard to understand. The situation might become slightly better by using the #error directive in yclass.h.
- So far tested only with GCC. Not everything might be portable, e.g. I am unsure about "VA_ARGS".
- So far tested only with examples consisting of a single .c file. While I have tried to forsee and circumvent linking errors, I have not tested it so far.
- YCLASS messes up the namespace. The macros declare functions and variables, do typedefs etc., with names that are invisible to the YCLASS user and only used internally. It is possible to accidentally run into such a name, which gives an error. More care should be taken in the implementation of YCLASS, e.g. by using some common prefix.
- In the current implementation, the method table is part of each object of one class. That means, if you have two objects of the same class, the method table for that class exists twice, certainly a waste of memory. It is thus not a good idea e.g. to define an "integer class" and to have a large array of it. This certainly needs improvement. The information concerning the class should better be kept separately.
- The system of signals and events is very simple, for some purposes maybe too simple. The same statement applies even more to the current form of exception handling.
- Documentation (see below) still needs significant improvement.
- There is no real world program written with YCLASS yet.
To use YCLASS, it suffices to include the header file yclass.h in your program.
#include <yclass.h>
Debug information is printed if YCLASS_DEBUG is defined:
#define YCLASS_DEBUG
#include <yclass.h>
For usage examples, see the files
example01.c
example02.c
example03.c
example04.c
example05.c
example06.c
example07.c
example08.c
example09.c
example10.c
example11.c
example12.c
example13.c
example14.c
example15.c
along with the comments therein.
These examples are meant to be read, compiled and run in ascending order. They should give you a good idea of the usage. While the documentation would certainly enjoy some improvement, the examples are now complete in the sense that I think they cover every aspect of YCLASS.