jestan

Programming Achievements: How to Level Up as a Developer

This gist is part of a blog post. Check it out at:

http://jasonrudolph.com/blog/2011/08/09/programming-achievements-how-to-level-up-as-a-developer

jestan

class A
class A2 extends A
class B

trait M[X]

//
// Upper Type Bound
//
def upperTypeBound[AA <: A](x: AA): A = x

jestan

/**
 * Part Zero : 10:15 Saturday Night
 *
 * (In which we will see how to let the type system help you handle failure)...
 *
 * First let's define a domain. (All the following requires scala 2.9.x and scalaz 6.0)
 */

import scalaz._
import Scalaz._

jestan

trait Enum { //DIY enum type
  import java.util.concurrent.atomic.AtomicReference //Concurrency paranoia

  type EnumVal <: Value //This is a type that needs to be found in the implementing class

  def withName(name: String): Option[EnumVal] = values.find(_.name == name)
  def withNameIgnoringCase(name: String): Option[EnumVal] = values.find(_.name.equalsIgnoreCase(name))

  private def lazyName(requestingInstance: EnumVal): String = {
    getClass().getMethods()

jestan

Caused by: org.h2.jdbc.JdbcSQLException: Invalid value "16" for parameter "scale (precision = -1)"; SQL statement:
create table agent_account (
    agent_id bigint not null,
    occ_version_number int not null,
    state int not null,
    balance decimal(-1,16) not null,
    account_id bigint not null primary key auto_increment,
    currency varchar(128) not null
  ) [90008-163]
	at org.h2.message.DbException.getJdbcSQLException(DbException.java:329)

jestan

 
#install vbox additions and create a shared dir called Shared in host OS
#switch to root and

mount -F vboxfs Shared <path to the local mount dir>

jestan

 # Fixed header - size 6 byes

 # variable length content 


 |--------- Header --------------| ----- content--|
 +--------+----------+-----------+----------------+    
 |  Tag   |  Seq No  |  Length   |  Content       |    
 | 0xCAFE |  0x0001  |  0x000C   | "HELLO, WORLD" |    
 +--------+----------+-----------+----------------+

jestan

# sudo sysctl -a | grep tcp

net.ipv4.tcp_timestamps = 1
net.ipv4.tcp_window_scaling = 1
net.ipv4.tcp_sack = 1
net.ipv4.tcp_retrans_collapse = 1
net.ipv4.tcp_syn_retries = 5
net.ipv4.tcp_synack_retries = 5
net.ipv4.tcp_max_orphans = 262144
net.ipv4.tcp_max_tw_buckets = 262144

jestan

import sbt._
import Keys._

object MyBuild extends Build {
  val ProjectVersion = "1.0"
  val Organization = "org.yit"
  val ScalaVersion = "2.9.1"

  val repositories = Seq("scala-tools.org" at "http://scala-tools.org/repo-releases")

jestan

#monitor the hard disk utilization  
iostat -xm 1

#monitor the cpu usage
sar -P ALL 1

#show disk usage
df -h