Compiler Design PROJECT PRESENTATION : COMPILER FOR OBJECTIVE C Harshal Waghmare Jeet Kumar Nandan Kumar Vishal Agrawal

Objective C: An Introduction The Objective-C language is defined as a small but powerful set of extensions to the standard C language., designed to give C full object-oriented programming capabilities. The Objective-C model of object-oriented programming is based on sending messages to sovereign objects. An object with method "method" is said to "respond" to the message method. [obj method:parameter]; Objective-C messages do not need to execute because they are dynamically bound.

Interfaces and implementations Objective-C requires the interface and implementation of a class be in separately declared code blocks. The interface is put in a header classname : superclassname { // instance variables } //class methods //instance The actual code is written in classname +classMethod { // implementation } -instanceMethod { // implementation

Instantiation This is done by first allocating the memory for a new object and then by initializing it. MyObject * o = [[MyObject alloc] init] Protocols An informal protocol is a list of methods which a class can implement. Dynamic typing An object can be sent a message that is not specified in its interface. Forwarding If message is sent to a object which might not respond to it, it forward the message on to an object which can respond to it. Posing Objective-C permits a class to wholly replace another class within a program

History & Evolution Hybrid between smalltalk and c. Created primarily by Brad Cox and Tom Love who began by modifying the C compiler to add some of the capabilities of Smalltalk. In 1988, Next released their own Objective-C compiler and libraries. The GNU Objective-C runtime which has been in use since 1993 is the one developed by Kresten Krab Thorup. Most of Apple's present-day Cocoa API is based on OpenStep interface objects, and is the most significant Objective-C environment being used for active development.

Why better than others? Objective-C messages do not need to execute because they are dynamically bound. If message is not implemented the code will still compile and run, unlike statically typed languages like C++. The Objective-C protocols is better than Java or C# concept of interfaces in that a class may implement a protocol without being declared to implement that protocol. Delegating methods to other objects and remote invocation can be easily implemented using categories and message forwarding. Instead of using an Enumerator object to iterate through a collection, Objective-C offers the fast enumeration syntax

Since ObjC is C plus Objects, it's very compatible with C (and now C++) code bases. Categories allow addition of methods to classes after the class's initial definition. We can redefine an existing method's implementation. Objective-C has a dynamic run-time. It allows crafting messages at run-time, dynamically creating classes, dynamically adding methods to existing classes, changing method implementations and so on. ObjC has real, fast, runtime message sending. #import appends a file only if it has not been already appended, unlike #include.

Progress till now Lexical Analysis : Completed Tool used : Lex Syntax Analysis : Completed Tool used : Yacc All implementations till now are in C, except that symbol table is implemented in C++.

Future Plans

Deadlines 28 th February : Syntax Analysis 15 th March : Semantic Analysis 30 th March : Intermediate Code Generation 10 th April : Final code Generation