Code Explainers

Code explainers tagged #recursion

java 
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

Building a trie for autocomplete in Java

trie prefix-tree recursion
Intermediate 8 steps
ruby 
class KeyTransformer
  def self.camelize(data)
    new.camelize(data)
  end

Recursively camelizing nested Ruby data

recursion data-transformation pattern-matching
Intermediate 7 steps
ruby 
require "yaml"
 
class FrontMatter
  DELIMITER = /\A---\s*\n(.*?)\n---\s*\n?(.*)\z/m

Parsing YAML front matter in Ruby

parsing regular-expressions yaml
Intermediate 8 steps
javascript 
const FRONTMATTER_RE = /^---\r?\n([\s\S]*?)\r?\n---\r?\n?/;
 
function coerce(value) {
  const trimmed = value.trim();

Parsing YAML-style frontmatter in JavaScript

parsing regular-expressions type-coercion
Intermediate 9 steps
java 
package com.example.validation;
 
import java.util.List;
import java.util.stream.Collectors;

Validating JSON payloads against a schema in Java

json-schema validation recursion
Intermediate 8 steps
python 
from typing import Any
 
_MISSING = object()
 

Recursively diffing two JSON structures

recursion sentinel tree-traversal
Intermediate 8 steps
php 
<?php
 
namespace App\Support;
 

Recursively finding files with SPL iterators in PHP

recursion iterators filesystem
Intermediate 7 steps
typescript 
type DeepPartial<T> = T extends object
  ? { [K in keyof T]?: DeepPartial<T[K]> }
  : T;
 

Type-safe deep merge in TypeScript

recursion conditional-types mapped-types
Advanced 7 steps
python 
from copy import deepcopy
from typing import Any, Mapping
 
 

How a recursive deep merge works in Python

recursion immutability dictionaries
Intermediate 6 steps
javascript 
function deepFreeze(obj) {
  const propNames = Reflect.ownKeys(obj);
 
  for (const name of propNames) {

Recursively freezing a nested object

recursion immutability object-freezing
Intermediate 6 steps
go 
package fsutil
 
import (
	"io/fs"

Walking a directory tree to find large files in Go

filesystem recursion closures
Intermediate 7 steps
ruby 
module DeepImmutable
  module_function
 
  def deep_freeze(obj)

Deep-freezing config with recursive immutability

immutability recursion deep-copy
Intermediate 8 steps
ruby 
class QueryParser
  def self.parse(query_string)
    new(query_string).parse
  end

Parsing nested query strings in Ruby

parsing recursion tokenization
Intermediate 9 steps
ruby 
require "yaml"
require "pathname"
 
class AppConfig

A typed config loader in Ruby

yaml configuration recursion
Intermediate 8 steps
rust 
use std::collections::HashMap;
 
#[derive(Debug, Clone)]
struct Row {

Building a tree from flat parent-id rows in Rust

recursion hashmap tree-building
Intermediate 6 steps
php 
function deepMerge(array $defaults, array $overrides): array
{
    foreach ($overrides as $key => $value) {
        if (

Recursively merging nested config arrays in PHP

recursion arrays configuration
Intermediate 6 steps
typescript 
type Curried<A extends any[], R> = A extends [infer First, ...infer Rest]
  ? (arg: First) => Rest extends [] ? R : Curried<Rest, R>
  : R;
 

Type-safe currying in TypeScript

currying conditional-types recursion
Advanced 8 steps
php 
<?php
 
function buildTree(array $items, ?int $parentId = null): array
{

Building a tree from a flat list in PHP

recursion tree grouping
Intermediate 6 steps