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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 APL
lists of maps tables (tab separated lines) rank 2 array (matrix)
-> ->> pipes, tee right to left execution
filter find, grep ⍳,⍸,∊,⍷,=,≡, etc.
map, apply call, xargs ¨
conditions test ≥,>,=,≠,≤,<,∨,∧, etc.
strings, regex sed, awk, tr character vectors, regex
Prismatic Graph make graphs
pmap parallel ¨

List Manipulation

Clojure Unix APL
conj, concat cat ,
take, drop head, tail ↑,↓
sort sort ⍒,⍋
count wc ≢
distinct uniq ∪
frequencies uniq -c {(⊣,≢)⌸⍵}
range seq ⍳
shuffle shuf {⍵[?⍨⍴⍵]}

Other Stuff

Clojure Unix APL
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!