Purescript on the BEAM: Getting Started

Published on 2018-11-6

Previous entries..

I guess the first thing we need to do is get some sort of environment up and running on my machine - seeing as this is a fork of Purescript with an Erlang backend and it's reasonably likely at some point I'm going to have to make a pull request or two, I settled with cloning the repo and running

stack build 
stack install

Haven't got stack? Well this isn't a tutorial, so you can Google that if you need to.

I then did the same for psc-package simply because I couldn't be bothered working out a different way, if it ain't broke then don't fix it - that's what I always say, my definition of broke is probably more lax than others though so YMMV.

Armed with a purescript compiler and a package manager, the next step is to obviously get something building.

I decided to base my meanderings off of pureerl_otp_sandbox at least as far as basic structure goes, although I did modify the makefile a tad so it looks a bit like this (I'm sure it's changed by the time anybody will read this, but close enough)

.PHONY: all clean

PS_SRC = ps_src
COMPILED_PS = src/compiled_ps
OUTPUT = output

all: $(COMPILED_PS)

$(COMPILED_PS): output
    mkdir -p $(COMPILED_PS)
    cp -pu $(OUTPUT)/*/*.erl $(COMPILED_PS)/
    touch $(COMPILED_PS)

output: $(PS_SRC)/**/*.purs $(PS_SRC)/*.purs .psc-package
    psc-package sources | xargs purs compile '$(PS_SRC)/**/*.purs'
    touch output

.psc-package: psc-package.json
    psc-package install
    touch .psc-package

clean:
    rm -rf $(OUTPUT)/*
    rm -f $(COMPILED_PS)/*

This is added to a hook in the rebar.config so it happens automatically on rebar3 compile

{pre_hooks,
  [
   {"(linux|darwin|solaris|win32)", compile, "make"},
   {"(linux|darwin|solaris|win32)", clean, "clean"}
  ]}.

Essentially, I can write an Erlang app as if ever ordinarily did, and as long as I have some .purs files in a folder called "ps_src" they'll get compiled into beam and everything will "just work".

My psc-package.json is about as stock as it gets at this point and just contains a pile of packages from the pureerl package set.

{
  "name": "untitled",
  "set": "erl-0.12.0-20180730",
  "source": "https://github.com/purerl/package-sets.git",
  "depends": [
    "console",
    "erl-atom",
    "erl-binary",
    "erl-lists",
    "erl-tuples",
    "erl-jsone",
    "maybe",
    "prelude"
  ]
}

This is probably already too long for most people to read when sat on the loo, so I'll leave the writing of any code at all to the next entry..

2018 © Rob Ashton. ALL Rights Reserved.