Add language feature description to readme

Readme.md

@@ -1,6 +1,183 @@
 # Qutes Lang
 A high level programming language for quantum computing.
 
+# Implemented Features
+## Variable Declaration and Assignment
+```csharp
+    bool a = true;
+    int b = 10;
+    string c = "Hello";
+    qubit d = 1q;
+    quint e = 10q;
+```
+
+## Variable Scope
+```csharp
+    bool b = false;
+    {
+        int b = 100; //this int b override the upper bool b.  
+    }
+    b = true; //this b refer to the bool b.
+```
+
+## Printing
+```csharp
+    int a = 10;
+    quint b = 10q;
+    print b;
+```
+
+## Branching
+```csharp
+    bool b = true;
+    if(b){
+        //Do something.
+    }
+
+    if(!b){
+        //Do something.
+    }
+    else{
+        //Do something else.
+    }
+
+    if(b){
+        //Do something.
+    }
+    else if(true){
+        //Do something else.
+    }
+```
+
+## Looping
+```csharp
+    bool b = true;
+    while(b){
+        //Do something while b == true.
+        b = false;
+    }
+
+    do{
+        //Do something until b == false.
+        b = true;
+    }
+    while(!b)
+```
+
+## Qubit declaration syntax
+```csharp
+    //alpha and beta values
+    qubit a = 0.7,0.3q;
+    //states we want the qubit is able to take
+    qubit b = [0, 1]q;
+    //shorter syntax for a qubit that take only the zero value
+    qubit c = 0q;
+    //special syntax for common superposition
+    qubit d = |+>;
+    qubit e = |->;
+```
+
+## Quint declaration syntax
+```csharp
+    //quint with 2^4 qubits that represent the number 10.
+    quint a = 10q;
+    //quint representing the number 1
+    quint b = [0q, 0q, 1q]; 
+    //quint with a superposition state where the most significant bit can be 0(70%) or 1(30%)
+    quint c = [0.7,0.3q, 0q, 1q];
+    //quint with a superposition state where the most significant bit can be 0(50%) or 1(50%) 
+    quint d = [[0, 1]q, 0q, 1q];
+    //quint with a superposition state that can be both 1(50%) or 3(50%)
+    quint e = [1, 3]q; 
+```
+
+## Quantum basic operations
+```csharp
+    qubit a = 1q;
+    qubit b = 1q;
+    not a;
+    pauliz a;
+    hadamard a;
+    quint c = a + b;
+```
+
+## Quantum circuit measurement
+```csharp
+    //Explicit measure
+    qubit a = [1]q;
+    qubit b = [1]q;
+    quint x = a + b;
+    measure x;
+
+    //Implicit measure
+    qubit a = [true]q;
+    qubit b = [true]q;
+    int classical = a + b;
+```
+
+# Features to implement
+## Branching on quantum functions and/or a mix of quantum and classical operations
+```csharp
+    if(grover_find()){
+        //do something
+    }
+    else{
+        //do something else
+    }
+```
+## Explicit casting
+```csharp
+    quint a = 1q;
+    qubit b = (qubit)a;
+```
+
+## Handle quantum scope
+```csharp
+    //This two blocks can be two different circuits.
+    {
+        qubit a = [true]q;
+        qubit b = [true]q;
+        quint x = a + b;
+        measure x;
+    }
+    {
+        quint c = 10q;
+        quint d = 4q;
+        quint re = d + c;
+        measure re;
+    }
+
+    //-----------
+
+    //This two blocks cannot be two different circuits because they use the same global variable.
+    //But we can say that we have two custom gate in the circuit,
+    //So if a custom gate doesn't take anything as input then it's a new circuit.
+    qubit a = [1]q;
+    {
+        qubit b = [1]q;
+        quint x = a + b;
+        measure x;
+    }
+    {
+        quint c = 10q;
+        quint re = c + a;
+        measure re;
+    }
+```
+
+## Functions
+```csharp
+    //easy to implement, create a new variable scope and execute the code inside.
+    public int sum(int a, int b){
+        return a + b;
+    }
+
+    //This could be implemented as a custom gate of the quantum circuit, but we need to handle the parameters allocation, release and the scope of the variables.
+    public quint sum(quint a, quint b){
+        return a + b;
+    }
+```
+
 ## How to Run
 ### 1. Install python requirements
 ```bash
@@ -19,4 +196,4 @@ python ./src/qutes.py ./specification/grammar/grammar_test.qut
 ```
 
 ### Notes
-You can follow the official antlr repository [starting guide for Python](https://github.com/antlr/antlr4/blob/master/doc/python-target.md) if you need a helping hand getting the environment ready.
+You can follow the official antlr repository [starting guide for Python](https://github.com/antlr/antlr4/blob/master/doc/python-target.md) if you need a help getting the environment ready.