Purescript on the BEAM: Getting Started

Previous entries..

• Intro

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..