fp-fundamentals_skill

Overview

This skill teaches core functional programming concepts: pure functions, currying, composition, and pointfree style. It focuses on practical patterns that make TypeScript code predictable, testable, and easy to compose. Learn guidelines and common pitfalls before using fp-ts types like Option, Either, and Task.

How this skill works

The skill examines how to write deterministic, side-effect-free functions and how to convert impure code into pure forms via dependency injection and data-last APIs. It demonstrates currying and partial application to enable reusable helpers, and shows composition (pipe/flow) and pointfree style to build clear pipelines. Each concept includes practical examples, common mistakes, and fixes you can apply immediately.

When to use it

• When you want functions that are easy to test and memoize
• When building reusable data transformation pipelines with pipe/flow
• Before introducing fp-ts types (Option, Either, Task) into your codebase
• When you need safe parallelizable logic without shared mutable state
• When composing small utilities into larger domain workflows

Best practices

• Prefer pure functions: return new values and inject dependencies instead of using globals
• Use data-last, curried functions to enable clean partial application and pipe usage
• Compose small, single-purpose functions and name grouped pipelines for readability
• Avoid over-currying: curry only to the level your callers need
• Make argument order consistent (config -> options -> data) across your codebase

Example use cases

• Transforming API responses through a typed pipeline that validates, maps, and formats data
• Creating reusable UI data mappers in React using curried map/filter helpers
• Turning impure database or I/O calls into Task/IO descriptions for controlled execution
• Building composable validation chains that return Either results for error handling
• Converting utility libraries to data-last functions so they work with pipe/flow