Prism

Prism is a small, strict, impure functional language in the ML family whose type system tracks side effects. Effects are inferred, extensible rows that combine structurally as functions call one another, and they track observability: an effect handled inside a function vanishes from its type. The core is a call-by-push-value calculus in A-normal form that compiles to native code through LLVM, with memory managed by deterministic reference counting and fully-in-place update rather than a garbage collector.

This book has two parts:

• Language Specification defines the surface language: lexical structure, grammar, types, effects, and evaluation.
• Compiler documents the implementation: the pipeline, the core calculus, effect lowering, reference counting, the backends, and the verification harness.

Use the Playground to edit, run, and inspect Prism code via an interpreter run in the browser.