context_fp_gleam

Functional programming context for Gleam

gleam add context_fp_gleam

Features

• 💉 Dependency injection without magic, only functions
• 🤌 Functions cached during workflow, no excess cost of CPU
• 💡 Smart type inference via generics
• ♻️ Unit tests friendly, feel free to pass mocked function in the Context

How to

Basic example

import context_fp_gleam.{cfp2}

let positive_numbers = fn(ns, _c) { list.filter(ns, fn(n) { n > 0 }) }
let numbers_prefix = fn(_ns, _c) { "Here is numbers: " }
let positive_numbers_as_string = {
 use ns, prefix <- cfp2(positive_numbers, numbers_prefix)
 prefix
 <> list.map(ns, fn(n) { int.to_string(n) })
 |> string.join(",")
}

// Here is numbers: 7,4
positive_numbers_as_string([-1, -5, 7, 0, 4], dict.new())

Calculations cached example

import context_fp_gleam.{cfp1,cfp2}

let positive_numbers = fn(ns, _c) {
 list.filter(ns, fn(n) { n > 0 }) // will be called only once
}
let positive_numbers_length = {
 use ns <- cfp1(positive_numbers)
 list.length(ns)
}
let positive_numbers_as_string = {
 use ns, length <- cfp2(positive_numbers, positive_numbers_length)
 list.map(ns, fn(n) { int.to_string(n) })
 |> string.join(",")
 <> "; length - "
 <> int.to_string(length)
}

// 7,4; length - 2
positive_numbers_as_string([-1, -5, 7, 0, 4], dict.new())

Dependency injection example

import context_fp_gleam.{cfp1}

let fetch_user_from_db = fn() { User("Petya") }
let fetch_user = fn(fetch_user_mock, _c) {
 option.unwrap(fetch_user_mock, fetch_user_from_db)()
}
let hello_world_user = {
 use user <- cfp1(fetch_user)
 "Hello world, " <> user.name
}

// Hello world, Vasya
hello_world_user(option.Some(fn() { User("Vasya") }), dict.new())

See also

• context-fp - Functional programming context for TypeScript
• context-fp-go - Functional programming context for Golang