How to update nested maps in Elixir with Pathex?

Use the `Pathex.update/3` function with a path created by `path/2`. For example, `path(:user / :name)` can update a name field efficiently. Check the cheatsheet for more examples on common operations.

Pathex vs Access: which is better for JSON manipulation?

Pathex is significantly faster and more composable, making it ideal for performance-critical JSON tasks. However, Access is built into Elixir and sufficient for simpler use cases without adding dependencies.

Is Pathex compatible with Elixir 1.17?

No, Pathex has critical bugs with Elixir 1.17 that block reliable usage, as stated in the README. It's recommended to use Elixir 1.18 or later, but note that 1.18 also has issues; always check the latest documentation.

How to compose paths in Pathex for reusable queries?

Use the `~>` operator to chain paths, like `path(:users) ~> all() ~> path(:name)`. This creates efficient, composable queries that can be reused across different data operations without performance loss.

What data structures does Pathex support beyond maps?

Pathex works with various nested structures including keyword lists, tuples, and can be extended to others like JSON, HTML, or Elixir AST via its flexible path-closure system, as mentioned in the features.

How does Pathex handle errors when a path is not found?

Pathex provides detailed error messages specifying the path and structure, making debugging easier. Functions return `{:error, reason}` or raise exceptions with context, unlike simpler tools that might fail silently.

Open-Awesome

pathex

BSD-2-ClauseElixir

A fast, composable functional lens library for manipulating nested data structures in Elixir.

GitHub

364 stars17 forks0 contributors

What is pathex?

Pathex is a library for performing fast actions with nested data structures in Elixir using the functional lens pattern. It allows developers to trivially set, get, and update values in structures in a functional manner, solving the problem of slow or limited data access in existing tools.

Target Audience

Elixir developers working with nested data structures who need efficient and composable data manipulation, such as those handling GenServer state, JSON, HTML, or AST transformations.

Value Proposition

Developers choose Pathex because it combines high performance (up to 160x faster than alternatives) with full composability, eliminating boilerplate code while providing an easy-to-use API similar to Elixir's standard library.

Overview

Fastest tool to access data in Elixir

Use Cases

Best For

Manipulating deeply nested maps and keyword lists in Elixir
Building reusable data access patterns for GenServer state
Transforming JSON structures efficiently
Working with HTML or Elixir AST in a functional way
Replacing boilerplate getter/setter functions in modules
Performance-critical data access where built-in `Access` is too slow

Not Ideal For

Projects running on Elixir 1.17 or 1.18 due to documented bugs that block reliable usage
Applications with flat or shallow data structures where Elixir's built-in Map and Keyword modules are sufficient
Teams that prioritize minimal dependencies and prefer standard library tools like Access for simple data access

Pros & Cons

Pros

Blazing Fast Performance

Uses pattern-matching compilation to achieve speeds up to 160x faster than Focus and 2-3x faster than built-in put_in/get_in, as verified in independent benchmarks.

Highly Composable Paths

Paths can be combined and reused for get, set, update, and delete operations without concatenation overhead, enabling efficient, reusable data access patterns.

User-Friendly API

Designed to be intuitive like Enum and Map, with clear error messages and a cheatsheet for common tasks, reducing boilerplate code.

Extensible Architecture

Built on a simple path-closure primitive, allowing any implementation complying with Pathex.t() spec to be integrated, fostering customization.

Cons

Version Compatibility Issues

Has known bugs with Elixir 1.17 and 1.18 that block reliable usage, requiring users to avoid these versions or wait for fixes, which can hinder adoption in legacy projects.

Niche Adoption and Ecosystem

As a specialized library, it has a smaller community and fewer third-party resources compared to standard Elixir data manipulation tools, limiting support and integrations.

Initial Learning Investment

Introduces the functional lens pattern, which may be unfamiliar to developers used to imperative or simpler functional approaches, despite the easy API, adding cognitive load.

Frequently Asked Questions

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