go-simplicity

go-simplicity

A Go-to-SimplicityHL transpiler for writing Bitcoin/Elements smart contracts in Go.

Write contract logic in idiomatic Go. The transpiler converts it to SimplicityHL — a typed, functional intermediate language that compiles to Simplicity bytecode for Bitcoin and Elements sidechains.

Quick Start

git clone https://github.com/0ceanslim/go-simplicity.git
cd go-simplicity
make build

./build/simgo -input examples/p2pk.go
./build/simgo -input examples/htlc.go
./build/simgo -input examples/vault.go

make test

What It Does

• Transpiles Go contracts — go run cmd/simgo/main.go -input contract.go prints ready-to-use SimplicityHL
• Witness/parameter separation — var sig [64]byte → mod witness; const Pubkey = 0x... → mod param
• Sum types — struct with IsLeft bool → Either<L, R>; struct with IsSome bool + Value T → Option<T>
• Match expression generation — if w.IsLeft { ... } else { ... } and switch { case w.IsLeft: ... } both compile to match witness::W { Left(...) => { ... }, Right(...) => { ... } }
• Boolean if/else — if boolVar { ... } else { ... } where boolVar is a jet result with type bool compiles to match boolVar { true => { ... }, false => { ... } }
• Helper function inlining — user-defined helper functions are emitted as named functions and inlined at call sites
• Operator mapping — +, -, *, /, %, <, <=, ==, &, |, ^ auto-map to the correct add_N/subtract_N/lt_N/and_N/etc. jet based on operand width
• SHA256Add auto-select — jet.SHA256Add(ctx, data) resolves to the correctly-sized sha_256_ctx_8_add_N variant at transpile time
• 102 jets registered across signature, hash, arithmetic, comparison, bitwise, time lock, transaction introspection, and Elements amount/issuance categories

Supported Contract Patterns

See docs/contract-patterns.md for Go source and generated SimplicityHL for each pattern.

Available Jets

102 jets registered. Quick reference by category:

Run simgo -list-jets to print the full list.

Types

Architecture

cmd/simgo/          # CLI binary (-input, -output, -target, -debug, -list-jets, -version)
pkg/
├── compiler/       # Validation and orchestration
├── jets/           # Jet registry (102 jets)
├── transpiler/     # Core Go → SimplicityHL AST walker
│   ├── transpiler.go   # Analysis, code generation, helper inlining
│   ├── patterns.go     # Either/Option match extraction, switch dispatch
│   └── arrays.go       # Fixed-size arrays
├── types/          # Type mapping (Go → Simplicity)
└── testkeys/       # BIP-340 spec test vectors
examples/           # 16 contract examples + 4 testable variants
tests/              # 60 tests

Not Supported

• Dynamic arrays, slices, maps, channels, goroutines, interfaces
• 3+ spending paths / nested Either (two arms only)
• Recursive function calls
• if/else inside helper function bodies (only main() supported)
• Imports other than simplicity/jet
• String types

Documentation

• Contract patterns & examples

Resources

• Simplicity Paper
• SimplicityHL repository
• Elements Project

License

MIT — see license for details.