circom by hairyf/blockchain-master

Skill is based on circom 2.x, generated at 2026-02-24.

circom is a domain-specific language and compiler for defining arithmetic circuits used in zero-knowledge proving systems (e.g. with snarkjs). Circuits are built from parameterized templates and components; the compiler outputs R1CS (and optionally WASM/C++ witness generators). This skill focuses on language semantics, constraint generation, and practical usage for agents.

Core References

Topic	Description	Reference
Signals	Input/output/intermediate, assignment operators, public/private, immutability	core-signals
Templates and components	Definition, instantiation, dot notation, arrays, parallel and custom templates	core-templates-components
Constraint generation	Quadratic constraints, ===, <== vs <-- + ===	core-constraints
Main component	Entry point, public input list, single main	core-main-component
Pragma and include	Version, custom_templates, include, -l	core-pragma-include

Features

Topic	Description	Reference
Operators	Field, boolean, relational, bitwise; precedence; conditional ? :	features-operators
Control flow	if/for/while, known vs unknown conditions, instantiation order	features-control-flow
Functions	Pure computations, no signals/constraints, return on every path	features-functions
Variables and data types	var, arrays (known size), field and signal arrays	features-variables-data-types
Anonymous components and tuples	Inline instantiation, multiple outputs, _, array <==	features-anonymous-tuples
Tags	Signal tags (e.g. binary, maxbit), inheritance, valued tags	features-tags
Buses	Struct-like signal groups, tagging, nested/parameterized, input format	features-buses
Compilation	CLI flags (r1cs, wasm, c, sym, O0/O1/O2, prime, -l, inspect)	features-compilation
Scoping	Signals/components at top-level or known-condition if; var block scope	features-scoping

Best Practices

Topic	Description	Reference
Signal safety	Prefer <==/==>; use <-- only when needed and add ===; use --inspect	best-practices-signal-safety
Assert and log	Compile-time vs witness-time assert; log() for debugging	best-practices-assert-log
Known vs unknown	Signals unknown; constraints and indices under known control flow	best-practices-unknowns
Simplification	When to use O0/O1/O2; PLONK vs Groth16; large circuits	best-practices-simplification