WorkLog

2018-02-11 (Sun)

Add an example of mapping from a resultset to a haskell record type. I think it's easier than by using template haskell. See example

2018-02-04 (Sun)

Add the parser which understand criteria, projection, order. See example

2017-10-31 (Tue)

I have finally closed the issue #7. I made hhe issue open about a week ago, but I came across the problem since when I started coding. Now my next challenge is to coding TLS connection.

2017-10-28 (Mon)

I made a presentation of the library.

https://atnd.org/events/91275

2017-10- ( )

Learning parser. I am reading ExprParser.java. This page is useful

Hare are methods to generate Expr.

parse orExpr parseLeftAssocBinaryOpExpr OR OROR andExpr parseLeftAssocBinaryOpExpr AND ANDAND ilriExpr IS, IN, LIKE, BETWEEN, REGEXP, NOT compExpr parseLeftAssocBinaryOpExpr GE, GT, LE, LT, EQ, NE bitExpr parseLeftAssocBinaryOpExpr BITAND, BITOR, BITXOR shiftExpr parseLeftAssocBinaryOpExpr LSHIFT, RSHIFT addSubExpr parseLeftAssocBinaryOpExpr PLUS, MINUS mulDivExpr parseLeftAssocBinaryOpExpr STAR, SLASH, MOD addSubIntervalExpr PLUS MINUS INTERVAL atomicExpr EROTEME , COLON , LPAREN , LCURLY , LSQBRACKET , CAST , PLUS , MINUS , NOT , NEG , BANG , LSTRING , NULL , LNUM_INT , LNUM_DOUBLE , TRUE , FALSE , DOLLAR , STAR , IDENT parenExprList ( , .. , .. ) used by IN, FUNCTION_CALL

parseLeftAssocBinaryOpExpr l = innerParse while (check BinaryOperator) r = inserParse l = BO l r

ex:

1 + 2 + 3 -> + (+ 1 2) 3 1 + 2 + 3 + 4 -> + (+ (+ 1 2) 3) 4

An experimental Code

package com.company;

import com.mysql.cj.xdevapi.ExprParser;

public class MyParser01 {

    public static void main(String[] args){
        System.out.println(new ExprParser(expr06).parse());
    }

    static String expr01 = "1 + 10 ";
    static String expr02 = "CASE WHEN 1>0 THEN 'true' ELSE 'false' END";// com.mysql.cj.core.exceptions.WrongArgumentException: Only 1 tokens consumed, out of 10
    static String expr03 = "max (capital)";
    static String expr04 = "max (distinct capital)"; // com.mysql.cj.core.exceptions.WrongArgumentException: Expected token type RPAREN at token pos 3
    static String expr05 = "1 + 2 + 3";
    static String expr06 = "1 + 2 + 3 + 4";

}

type: OPERATOR
operator {
  name: "+"
  param {
    type: OPERATOR
    operator {
      name: "+"
      param {
        type: OPERATOR
        operator {
          name: "+"
          param {
            type: LITERAL
            literal {
              type: V_SINT
              v_signed_int: 1
            }
          }
          param {
            type: LITERAL
            literal {
              type: V_SINT
              v_signed_int: 2
            }
          }
        }
      }
      param {
        type: LITERAL
        literal {
          type: V_SINT
          v_signed_int: 3
        }
      }
    }
  }
  param {
    type: LITERAL
    literal {
      type: V_SINT
      v_signed_int: 4
    }
  }
}

2017-10-08 (Sun)

Proxy ScreenShot

Now proxy working! 🎉

Need to refactor code.

Basic Pitfall

I've fallen into an error as follows:

*** Exception: src/PPrint01.hs:(89,1)-(98,131): Non-exhaustive patterns in function myFunc

Haskell is a strongly typed language, so I never thought I got such an error. I was wondering hours. The reason is very simple. I just forgot handling empty list.

buzz :: [Char] -> Bool
buzz (x:xs) = x == 'a'

 > buzz "ab"
True
 > buzz "xb"
False
 > buzz ""
*** Exception: src/PPrint01.hs:113:1-22: Non-exhaustive patterns in function buzz

Need to add.

buzz [] = False

I am still a beginner. 😢

Message Record Formatting

I'm working on a proxy facility for the library and trying to implement logging for messages. I use Text.Pretty.Simple package, which is fine. But the output of a message is a little bit noisy, because Nothing fields are displayed. For example

Right
    ( PCS
        ( CapabilitiesSet
            { capabilities = Capabilities
                { capabilities = fromList
                    [ Capability
                        { name = "client.pwd_expire_ok"
                        , value = Any
                            { type' = SCALAR
                            , scalar = Just
                                ( Scalar
                                    { type' = V_BOOL
                                    , v_signed_int = Nothing    -- (*)
                                    , v_unsigned_int = Nothing    -- (*)
                                    , v_octets = Nothing    -- (*)
                                    , v_double = Nothing    -- (*)
                                    , v_float = Nothing    -- (*)
                                    , v_bool = Just True    -- (##)
                                    , v_string = Nothing    -- (*)
                                    }
                                )
                            , obj = Nothing
                            , array = Nothing
                            }
                        }
                    ]
                }
            }
        )
    )

You notice the Scalar record above has only a boolean value (##), but other values (*) are printed. So I am trying to remove Nothing values.

2017-10-07 (Sat)

Writing client library for a database requires much knowledge, not only MySQL but also other areas. I noticed that I don't know network programing well. So now I am reading TCP/IP Sockets in C: Practical Guide for Programmers (The Practical Guides) (Yes I am reading the Japanese translated Version. 😀 ). Though the book published about 15 years ago, it's not outdated. I haven't finished yet, but I think it explains TCP/IP programming short and concise.