Update clang-repl documentation

[Krishna-13-cyber]

Summary

Update Clang-repl documentation with:-

• Add usage and build instructions
• Add examples depicting their usage in clang-repl.

[v.g.vassilev]

I think this is heading in a good direction. Please find some comments inline.

clang/docs/ClangRepl.rst

220

229

I find it surprising to see the build instructions as part of the "usage" section. Can you move it out?

248

A typo?

[Krishna-13-cyber]

• Update with addressing the comments.

[v.g.vassilev]

clang/docs/ClangRepl.rst

119

120

145

146

We can use \ to break lines.

[Krishna-13-cyber]

• Update with addressing the comments
• Update with example of Dynamic library usage in repl

[Krishna-13-cyber]

• Update with addressing the comments

[v.g.vassilev]

LGTM! If you don't have commit access I can commit this on your behalf.

[Krishna-13-cyber]

In D152109#4464563, @v.g.vassilev wrote:

LGTM! If you don't have commit access I can commit this on your behalf.

Yes,
It would be great if you could land it on my behalf!
Thanks.

clang/docs/ClangRepl.rst

 Clang-Repl is suitable for exploratory programming and in places where time
 to insight is important. Clang-Repl is a project inspired by the work in
 `Cling <https://github.com/root-project/cling>`_, a LLVM-based C/C++ interpreter
 developed by the field of high energy physics and used by the scientific data
 analysis framework `ROOT <https://root.cern/>`_. Clang-Repl allows to move parts
 of Cling upstream, making them useful and available to a broader audience.
 
 
-
-Clang-Repl Usage
-================
-
-
-.. code-block:: text
-
-  clang-repl> #include <iostream>
-  clang-repl> int f() { std::cout << "Hello Interpreted World!\n"; return 0; }
-  clang-repl> auto r = f();
-  // Prints Hello Interpreted World!
-
-Note that the implementation is not complete and highly experimental. We do
-not yet support statements on the global scope, for example.
-
-
 Clang-Repl Basic Data Flow
 ==========================
 
 .. image:: ClangRepl_design.png
    :align: center
    :alt: ClangRepl design
 
 Clang-Repl data flow can be divided into roughly 8 phases:
6. The LLVM IR is the input format for LLVM’s JIT compilation infrastructure.
    The tool will instruct the JIT to run specified functions, translating them
    into machine code targeting the underlying device architecture (eg. Intel
    x86 or NVPTX).
 
 7. The LLVM JIT lowers the LLVM IR to machine code.
 
 8. The machine code is then executed.
 
+===================
+Build Instructions:
+===================
+
+
+.. code-block:: console
+
+   $ cd llvm-project
+   $ mkdir build
+   $ cd build
+   $ cmake -DCMAKE_BUILD_TYPE=RelWithDebInfo -DLLVM_ENABLE_PROJECTS=clang -G "Unix Makefiles" ../llvm
+
+**Note here**, above RelWithDebInfo - Debug / Release
+
+.. code-block:: console
+
+   cmake --build . --target clang clang-repl -j n
+      OR
+   cmake --build . --target clang clang-repl
+
+**Clang-repl** is built under llvm-project/build/bin. Proceed into the directory **llvm-project/build/bin**
+
+.. code-block:: console
+
+   ./clang-repl
+   clang-repl>
+
+
+================
+Clang-Repl Usage
+================
+
+**Clang-Repl** is an interactive C++ interpreter that allows for incremental
+compilation. It supports interactive programming for C++ in a
+read-evaluate-print-loop (REPL) style. It uses Clang as a library to compile the
+high level programming language into LLVM IR. Then the LLVM IR is executed by
+the LLVM just-in-time (JIT) infrastructure.
+
+
+Basic:
+======
+
+.. code-block:: text
+
+  clang-repl> #include <iostream>
+  clang-repl> int f() { std::cout << "Hello Interpreted World!\n"; return 0; }
+  clang-repl> auto r = f();
+   // Prints Hello Interpreted World!
+
+.. code-block:: text
+
+   clang-repl> #include<iostream>
+   clang-repl> using namespace std;
+   clang-repl> std::cout << "Welcome to CLANG-REPL" << std::endl;
+   Welcome to CLANG-REPL
+   // Prints Welcome to CLANG-REPL
+
+
+Function Definitions and Calls:
+===============================
+
+.. code-block:: text
+
+   clang-repl> #include <iostream>
+   clang-repl> int sum(int a, int b){ return a+b; };
+   clang-repl> int c = sum(9,10);
+   clang-repl> std::cout << c << std::endl;
+   19
+   clang-repl>
+
+Iterative Structures:
+=====================
+
+.. code-block:: text
+
+   clang-repl> #include <iostream>
+   clang-repl> for (int i = 0;i < 3;i++){ std::cout << i << std::endl;}
+   0
+   1
+   2
+   clang-repl> while(i < 7){ i++; std::cout << i << std::endl;}
+   4
+   5
+   6
+   7
+
+Classes and Structures:
+=======================
+
+.. code-block:: text
+
+   clang-repl> #include <iostream>
+   clang-repl> class Rectangle {int width, height; public: void set_values (int,int);\
+   clang-repl... int area() {return width*height;}};
+   clang-repl>  void Rectangle::set_values (int x, int y) { width = x;height = y;}
+   clang-repl> int main () { Rectangle rect;rect.set_values (3,4);\
+   clang-repl... std::cout << "area: " << rect.area() << std::endl;\
+   clang-repl... return 0;}
+   clang-repl> main();
+   area: 12
+   clang-repl>
+   // Note: This '\' can be used for continuation of the statements in the next line
+
+Lamdas:
+=======
+
+.. code-block:: text
+
+   clang-repl> #include <iostream>
+   clang-repl> using namespace std;
+   clang-repl> auto welcome = []()  { std::cout << "Welcome to REPL" << std::endl;};
+   clang-repl> welcome();
+   Welcome to REPL
+
+Using Dynamic Library:
+======================
+
+.. code-block:: text
+
+   clang-repl> %lib print.so
+   clang-repl> #include"print.hpp"
+   clang-repl> print(9);
+   9
+
+**Generation of dynamic library**
+
+.. code-block:: text
+
+   // print.cpp
+   #include <iostream>
+   #include "print.hpp"
+
+   void print(int a)
+   {
+      std::cout << a << std::endl;
+   }
+
+   // print.hpp
+   void print (int a);
+
+   // Commands
+   clang++-17  -c -o print.o print.cpp
+   clang-17 -shared print.o -o print.so
+
+Comments:
+=========
+
+.. code-block:: text
+
+   clang-repl> // Comments in Clang-Repl
+   clang-repl> /* Comments in Clang-Repl */
+
+
+Closure or Termination:
+=======================
+
+.. code-block:: text
+
+   clang-repl>%quit
+
 
-Just like Clang, Clang-Repl can be integrated in existing applications as a
-library (via using the clangInterpreter library). This turning your C++ compiler
-into a service which incrementally can consume and execute code. The
-**Compiler as A Service** (**CaaS**) concept helps supporting move advanced use
-cases such as template instantiations on demand and automatic language
-interoperability. It also helps static languages such as C/C++ become apt for
-data science.
+Just like Clang, Clang-Repl can be integrated in existing applications as a library
+(using the clangInterpreter library). This turns your C++ compiler into a service that
+can incrementally consume and execute code. The **Compiler as A Service** (**CaaS**)
+concept helps support advanced use cases such as template instantiations on demand and
+automatic language interoperability. It also helps static languages such as C/C++ become
+apt for data science.
 
 
 Related Reading
 ===============
 `Cling Transitions to LLVM's Clang-Repl <https://root.cern/blog/cling-in-llvm/>`_
 
 `Moving (parts of) the Cling REPL in Clang <https://lists.llvm.org/pipermail/llvm-dev/2020-July/143257.html>`_
 
 `GPU Accelerated Automatic Differentiation With Clad <https://arxiv.org/pdf/2203.06139.pdf>`_