Update README.md

Author: harmya

README.md

@@ -1,3 +1,60 @@
 ### Writing a compiler from scratch
 
-Yes
+Parts of a compiler: 
+- Lexer
+- Parser
+- Semantic Analysis
+- IR Generation
+- Optimization Passes
+- Code Generation
+
+I might skip the backend and make this an interpreter (easier?)
+
+Current progress:
+
+Lexer: Done
+Consider a program as a long string, loop through it token by token, and assign each token.
+Each Token can be: 
+``` rust
+pub enum Token {
+    // Delimiters
+    Comma,
+    LeftParen,
+    RightParen,
+    LeftBrace,
+    RightBrace,
+    SemiColon,
+    DoubleQuote,
+    // Operators
+    Add,
+    Sub,
+    Mul,
+    Div,
+    Mod,
+    NotEqual,
+    EqualEqual,
+    Greater,
+    GreaterEqual,
+    Less,
+    LessEqual,
+    Equal,
+    Not,
+    Or,
+    And,
+    // Literals
+    Number(i32),
+    Boolean(bool),
+    Identifier(String),
+    StringLiteral(String),
+    // Keywords
+    Func,
+    Main,
+    If,
+    Else,
+    For,
+    While,
+    Let,
+    Return,
+    Print,
+}
+```