update README

README.md

@@ -21,4 +21,17 @@ This outputs
 AST: SQLSelect { projection: [SQLIdentifier("a"), SQLIdentifier("b"), SQLLiteralLong(123), SQLFunction { id: "myfunc", args: [SQLIdentifier("b")] }], relation: Some(SQLIdentifier("table_1")), selection: Some(SQLBinaryExpr { left: SQLBinaryExpr { left: SQLIdentifier("a"), op: Gt, right: SQLIdentifier("b") }, op: And, right: SQLBinaryExpr { left: SQLIdentifier("b"), op: Lt, right: SQLLiteralLong(100) } }), order_by: Some([SQLOrderBy { expr: SQLIdentifier("a"), asc: false }, SQLOrderBy { expr: SQLIdentifier("b"), asc: true }]), group_by: None, having: None, limit: None }
 ```
 
+## Design
+
+This parser is implemented using the [Pratt Parser](https://tdop.github.io/) design, which is a top-down operator-precedence parser.
+
+I am a fan of this design pattern over parser generators for the following reasons:
+
+- Parsing code is simple to write and can be concise and elegant (this is far from true for this current implementation unfortunately, but I hope to fix that using some macros)
+- Performance is generally better than code generated by parser generators
+- Debugging is much easier with hand-written code
+- It is far easier to extend and make dialect-specific extensions compared to using a parser generator
+
+## Contributing
+
 Please get involved in helping build first class SQL support in Rust by filing issues for missing features (there are plenty!) and create pull requests.