The Bosatsu Programming Language

Bosatsu (菩薩) is the transliteration in Japanese of the sanskrit bodhisattva. A bodhisattva is someone who can reach enlightenment but decides not to, to help others achieve that goal. -- Wikipedia

Bosatsu is a simple, non-turing complete language designed for configuration, queries and scripting. It borrows from Python, Haskell, Dhall and Rust.

An example of Bosatsu

Here is a working Bosatsu program to solve the first Project Euler problem:

package Euler/One

# see:
# https://projecteuler.net/problem=1
# Find the sum of all the multiples of 3 or 5 below 1000.

operator == = eq_Int
operator % = mod_Int

def operator ||(x, y):
  True if x else y

def keep(i):
  (i % 3 == 0) || (i % 5 == 0)

def sum(as): as.foldLeft(0, add)

# >>> sum(i for i in xrange(1000) if keep_fn(i))
# 233168
computed = [i for i in range(1000) if keep(i)].sum

test = Assertion(computed == 233168, "expected 233168")

For more details see the language guide in particular the section on syntax. For vim syntax files see bosatsu.vim.

Getting started

You can try basic expressions using this in-browser Bosatsu compiler. To work locally, clone this repo, then build the compiler:

sbt cli/assembly

Now try running the above program:

./bosatsuj eval --main Euler/One::computed --input test_workspace/euler1.bosatsu

The command ./bosatsuj has pretty complete help if you run it with no arguments. If you have graal native-image on your path, after building with sbt cli/assembly you can build the native image:

./build_native.sh

Now you should have ./bosatsu available which is MUCH faster to use than ./bosatsuj which has to pay the JVM startup cost on each call, e.g.:

oscar@oscar-XPS-13-7390:~/oss/bosatsu$ time bosatsu eval --main Euler/One::computed --input test_workspace/euler1.bosatsu 
233168: Bosatsu/Predef::Int

real    0m0.161s
user    0m0.085s
sys     0m0.051s
oscar@oscar-XPS-13-7390:~/oss/bosatsu$ time ./bosatsuj eval --main Euler/One::computed --input test_workspace/euler1.bosatsu 
233168: Bosatsu/Predef::Int

real    0m2.260s
user    0m4.621s
sys     0m0.155s

Use cases

Currently we have implemented type-checking, the package system, and an interpreter to evalute expressions and tests. This could already be useful if you want to give some programmability to configuration that can load, type-check and evaluate the configuration before executing the rest of the scala or java code.

As a JSON templating engine

Bosatsu can be used as a JSON generation system, which could be useful for generating complex configurations in a way that has type-checking and ability to compose.

Using the bosatsu json command you can convert bosatsu expressions into json.

This gives you a programmatic way to generate JSON in a limited language (no IO, no infinite recursion, totally reproducible).

An example is the dependencies file used by the bazel build of this repo:

./bosatsuj json write --package_root test_workspace --input_dir test_workspace --main_file test_workspace/gen_deps.bosatsu

Bazel rules

This repo include bazel rules to call bosatsu so you can build libraries, write tests, and generate json using bosatsu and Bazel. For a working example see this example.

cd test_workspace
bazel build ...
cat bazel-build/testjson.json

Future features

We would like to implement a number of features:

a REPL or Notebook experience.
a java backend and bazel rules which can call java and scala functions
a skylark backend to allow writing strongly typed bazel rules compiling to untyped skylark

How to run the benchmarks

bench/jmh:run -i 3 -wi 3 -f1 -t1

or for a specific benchmark

bench/jmh:run -i 3 -wi 3 -f1 -t1 .*SomeBench.*

honkfestival/bosatsu