Hey, this is my blog

Git Custom Merge Drivers

June 16, 2016 - git merging

Git merge drivers.

Postgres Update With Join

April 20, 2016 - postgres cte update

How to perform and update with a join using CTE’s in postgres

• in a cte, write a select that returns the update to values, and the join on conditions
• join on that in the update
• Test: Optionally write a select that tests your results and wrap it all in a rolled back transaction to test run

Using Custom Packages in NixOs Configuration File

March 26, 2016 - nix nixos

Here is a problem we encountered with NixOS:

The nix-channel we were on didn’t have the latest version of something we needed. This happened recently when my coworker upgraded to Postgres 9.5 from 9.4 but the PostGIS version in nixpkgs hadn’t been updated to a 9.5 compatible version.

Bitcoin Transactions

November 4, 2015 - prediction good-judgement-project bitcoin

What will be the average number of Bitcoin transactions per day in the first week of June 2016?

Fitness Books

October 21, 2015 - fitness books

I’ve read a lot of fitness biographies over the last little while. Here is a quick list.

More Scala Groups And Tuples

August 19, 2015 - scala slick tuples

Continuing from here, I have lists of tuples and I want to group them. Here I have a list of 4-tuples and I want to group the second tuple by the first. The fact that I need to do this probably represents some greater problem, but that is a story for another time

import shapeless._
import syntax.std.tuple._
import poly._

object GroupLists {
def group1TwoExtra[A,B,C,D](t : List[(A,B,C,D)]) : List[(A,List[B],C,D)] = {
      val map = LinkedHashMap[A, LinkedHashSet[B]]()
      val mapOther = scala.collection.mutable.Map[A,(C,D)]()
      for (i <- t) {
        val key = i.head
        map(key) = map.lift(key).getOrElse(LinkedHashSet[B]()) + i.drop(1).head
        mapOther += (key -> i.drop(2))
      }
      map.map(b => (b._1, b._2.toList) ++ mapOther(b._1)).toList
    }

Mixed Metaphors

August 11, 2015 - humor presentation

Here I’m collecting some mixed metaphors that I thought were funny. Hopefully for use in a presentation about comedy I am doing

• I wouldn’t eat that with a ten foot pole

Scala Slick Group

August 4, 2015 - scala slick

In slick, if each foo has many bars and I need to retrive several foos and associtated bars I will do something like this:

val join = for {
     (f,b) <-
                  foo.filter(...) on  innerJoin
                  bar on (...)
   } yield (o,i,s)

Hakyll and CircleCi

July 31, 2015 - blog hakyll ci haskell

This blog was on tumblr, which was easy to setup and post and such. However, I spend like 8 hours a day with a text editor open and a git in terminal window.

Lazy Evaluation In Haskell

January 14, 2015

This post is a work in progress and represents my getting to understand how laziness works in haskell and how it affects performance.