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Clojure and Unix

Learning Clojure

  • learning Clojure can be hard
  • I was used to imperative programming: Perl, Python, JavaScript, Java
  • my code was full of for loops and if statements

Data Flow

  • immutable data and the ->> macro changed my life
  • I had to stop thinking of my code as poking at the data
  • I started thinking of data flowing through code

Tables and Batches

  • most of my Clojure code does batch processing
  • source data usually comes from tables: CSV, SQL, Excel
  • I convert rows to maps, tables to lists of maps
  • I define little functions for updating those maps
  • I work with lists of maps using filter and map
  • I use Prismatic's Graph library to build a dependency graphs of tasks

Annoyances

  • I'm a functional programming convert
  • Clojure is my favourite language
  • but there are annoyances!
    • Clojure is too heavy for scripting tasks
    • the JVM is its own universe
    • getting Clojure adopted can be hard
  • for a lot of stuff, I just can't use Clojure

The Old Ways

  • the older I get, the more I appreciate old tools and code
    • Vim for everything
    • live in the terminal
    • write Lisp
  • I've written enough crap using the "shiny new thing"
  • I don't have time to reinvent the wheel

Mental Block

  • when I was an imperative programmer ...
    • I loved Python: modern, clean, consistent syntax
    • I hated Bash: arcane symbols, imperative structures feel tacked on
  • Bash didn't suit my programming mindset
  • I didn't bother to learn more ...
  • I only used the shell for one-liners

Change is Slow

  • I started collecting my one-liners in Makefiles
  • I started writing two-liners and three-liners
  • I started adding more Unix tools to my toolkit
  • I never had to write any for loops in Bash
  • things were great!

A Second Look

  • my Clojure code is
    • full of little functions
    • grouped into pipelines
    • processing lists of rows
    • connected in dependency graphs
  • but I was using Unix to write
    • little tool executions
    • grouped into pipelines
    • processing lists of rows
    • connected in dependency graphs

Strangely Similar

Clojure Unix
lists of maps tables (tab separated lines)
-> ->> pipes, tee
filter find, grep
map, apply call, xargs
conditions test
strings, regex sed, awk, tr
Prismatic Graph make
pmap parallel

List Manipulation

Clojure Unix
conj, concat cat
take, drop head, tail
sort sort
count wc
distinct uniq
frequencies uniq -c
range seq
shuffle shuf

Other Stuff

Clojure Unix
slurp curl
assoc, dissoc cut, join
println echo
str, format paste, printf

But, but, but!

  • REPL: the shell is your REPL!
  • obscure syntax:
    • you got used to parens!
    • many people are more comfortable with the shell
  • mutability, concurrency:
    • write to a new location
    • pipes are efficient (like transducers!)
  • Windows support: use Vagrant, VMs
  • fancy algorithms: use Clojure for the tricky parts
  • fancy data structures: use Clojure for that part
  • servers: fine, use Clojure

Upshot

Clojure and Unix tools are both focused on processing sequences of lightweight data structures through composable pipelines.

Closing Thoughts

  • the more deeply I understand how great Clojure is, the less I use it
  • Unix tools are usually lighter and faster, and easier to integrate with other tools
  • use Clojure for the hard parts!