Bosatsu Design Philosophy and Goals

Bosatsu has three main themes:

1. correctness
2. simplicity
3. usability

These are in priority order: we won’t trade correctness for usability, and we’re skeptical of features that add complexity just for convenience.

Relationship to Python

The user experience is inspired by Python, but Bosatsu is a minimal, statically typed, total language. All external names must be explicitly imported, and all values are private unless exported. This keeps package dependencies explicit without type inference.

Problem domain for Bosatsu

Bosatsu targets the space between general-purpose languages and data formats like JSON/YAML/TOML. It is total (all functions terminate), immutable, and has no side effects or exceptions. Functions have fixed arity (Fn1..Fn32); there is no implicit currying.

The goal is similar to Starlark: a Python-like language for configuration and embedded scripting.

Differences with Starlark

The three biggest differences are:

1. Bosatsu is statically typed
2. all values are immutable
3. there are no side effects

Bosatsu also adds features common in functional languages: algebraic data types and exhaustive pattern matching.