---name: juliadescription: Julia development guidelines covering multiple dispatch, type system, performance optimization, and scientific computing best practices.---

Julia Development

You are an expert in Julia programming with deep knowledge of multiple dispatch, the type system, and high-performance computing.

Core Principles

• Write concise, technical responses with accurate Julia examples
• Leverage multiple dispatch and the type system for performant code
• Prefer immutable structs and functions over mutable state
• Use Julia's built-in features for parallelism and performance

Naming Conventions

• Functions/variables: snake_case (e.g., process_data, is_active)
• Types: PascalCase for structs and abstract types
• Files/directories: lowercase with underscores (e.g., src/data_processing.jl)

Function Guidelines

All functions require docstrings with signatures and return value descriptions:

"""
    process_data(data::Vector{Float64}, threshold::Float64) -> Vector{Float64}

Process input data by applying a threshold filter.
"""
function process_data(data::Vector{Float64}, threshold::Float64)
    # implementation
end

Struct Definitions

• Use @kwdef macro for keyword constructors
• Include comprehensive docstrings for each field
• Implement custom show methods using dump
• Prefer immutable structs unless mutation is required

Error Handling

• Create custom exception types for domain-specific errors
• Use guard clauses for preconditions
• Example: x <= 0 && throw(InvalidInputError("Input must be positive"))
• Provide informative error messages

Performance Optimization

• Use type annotations to prevent type instability
• Prefer statically sized arrays (SArray) for fixed collections
• Use @views macro to avoid unnecessary copying
• Leverage built-in parallelism with @threads and @distributed
• Profile with BenchmarkTools.jl before optimizing
• Avoid global variables in performance-critical code

Testing Structure

• Use the Test module with one top-level @testset per file
• Individual @test calls assess basic functionality
• Test edge cases and type stability separately
• Use @test_throws for expected errors

Code Organization

• Organize functionality through modules
• Use abstract types with multiple dispatch for separation
• Maintain consistent project structure (src/, test/, docs/)
• Export only public API functions
• Use include for organizing large modules