Syntax

JavaScript Web

// Async HTTP fetch with exponential-backoff retry
const MAX_RETRIES = 3;

async function fetchWithRetry(url, options = {}, retries = MAX_RETRIES) {
  try {
    const response = await fetch(url, {
      headers: { 'Content-Type': 'application/json', ...options.headers },
      ...options,
    });
    if (!response.ok) {
      throw new Error(`HTTP ${response.status}: ${response.statusText}`);
    }
    return await response.json();
  } catch (err) {
    if (retries > 0) {
      const delay = 2 ** (MAX_RETRIES - retries) * 200;
      console.warn(`Retrying in ${delay}ms… (${retries} left)`);
      await new Promise((res) => setTimeout(res, delay));
      return fetchWithRetry(url, options, retries - 1);
    }
    throw err;
  }
}

// Binary-search tree — in-order traversal
class TreeNode {
  constructor(val, left = null, right = null) {
    this.val   = val;
    this.left  = left;
    this.right = right;
  }
}

function inorder(node, result = []) {
  if (!node) return result;
  inorder(node.left, result);
  result.push(node.val);
  inorder(node.right, result);
  return result;
}

const tree = new TreeNode(4,
  new TreeNode(2, new TreeNode(1), new TreeNode(3)),
  new TreeNode(6, new TreeNode(5), new TreeNode(7)),
);

console.log(inorder(tree)); // [1, 2, 3, 4, 5, 6, 7]

// Iterator protocol
function* range(start, end, step = 1) {
  for (let i = start; i < end; i += step) yield i;
}

const evens = [...range(0, 20, 2)];
console.log(evens);

TypeScript Web

// Generic Result type for typed error handling
type Result<T, E = Error> =
  | { ok: true; value: T }
  | { ok: false; error: E };

const ok  = <T>(value: T): Result<T>        => ({ ok: true,  value });
const err = <E>(error: E): Result<never, E>  => ({ ok: false, error });

// Typed API model
interface ApiUser {
  id:        number;
  name:      string;
  email:     string;
  role:      'admin' | 'user' | 'guest';
  createdAt: string;
}

async function getUser(id: number): Promise<Result<ApiUser>> {
  try {
    const res = await fetch(`/api/users/${id}`);
    if (!res.ok) return err(new Error(`Status ${res.status}`));
    return ok(await res.json() as ApiUser);
  } catch (e) {
    return err(e instanceof Error ? e : new Error(String(e)));
  }
}

void (async () => {
  const result = await getUser(42);
  if (result.ok) {
    const { name, role } = result.value;
    console.log(`${name} is a ${role}`);
  } else {
    console.error('Failed:', result.error.message);
  }
})();

// Mapped and conditional types
type Nullable<T>  = { [K in keyof T]: T[K] | null };
type Readonly2<T> = { readonly [K in keyof T]: T[K] };
type IsString<T>  = T extends string ? true : false;
type Flatten<T>   = T extends Array<infer U> ? U : T;

// Class decorator
function sealed(ctor: Function): void {
  Object.seal(ctor);
  Object.seal(ctor.prototype);
}

@sealed
class UserCache {
  private cache = new Map<number, ApiUser>();

  set(user: ApiUser): void {
    this.cache.set(user.id, user);
  }

  get(id: number): ApiUser | undefined {
    return this.cache.get(id);
  }
}

// Memoised Fibonacci with Map
const memo = new Map<number, bigint>();

function fib(n: number): bigint {
  if (n <= 1) return BigInt(n);
  if (memo.has(n)) return memo.get(n)!;
  const result = fib(n - 1) + fib(n - 2);
  memo.set(n, result);
  return result;
}

console.log(Array.from({ length: 10 }, (_, i) => fib(i)));

Python Scripting

from __future__ import annotations
import asyncio
import re
from dataclasses import dataclass, field
from typing import AsyncIterator


@dataclass
class TextProcessor:
    text: str
    stop_words: set[str] = field(
        default_factory=lambda: {"the", "a", "an", "is", "in", "on"}
    )

    def tokenize(self) -> list[str]:
        pattern = re.compile(r"\b[a-zA-Z']+\b")
        return [t.lower() for t in pattern.findall(self.text)]

    def word_freq(self) -> dict[str, int]:
        freq: dict[str, int] = {}
        for word in self.tokenize():
            if word not in self.stop_words:
                freq[word] = freq.get(word, 0) + 1
        return dict(sorted(freq.items(), key=lambda x: x[1], reverse=True))

    def top_n(self, n: int = 5) -> list[tuple[str, int]]:
        return list(self.word_freq().items())[:n]


async def stream_chunks(data: str, chunk_size: int = 8) -> AsyncIterator[str]:
    """Async generator simulating a streaming API response."""
    for i in range(0, len(data), chunk_size):
        await asyncio.sleep(0.01)
        yield data[i : i + chunk_size]


async def main() -> None:
    sample = "The quick brown fox jumps over the lazy dog " * 3
    processor = TextProcessor(sample)

    print("Top words:", processor.top_n(5))

    chunks: list[str] = []
    async for chunk in stream_chunks(sample):
        chunks.append(chunk)
    print(f"Received {len(chunks)} chunks, total {sum(len(c) for c in chunks)} chars")


if __name__ == "__main__":
    asyncio.run(main())

Rust Systems

use std::collections::HashMap;
use std::fmt;

#[derive(Debug)]
enum StackError {
    Empty,
    Overflow(usize),
}

impl fmt::Display for StackError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            StackError::Empty        => write!(f, "stack is empty"),
            StackError::Overflow(n) => write!(f, "stack capacity ({n}) exceeded"),
        }
    }
}

struct Stack<T> {
    data: Vec<T>,
    capacity: usize,
}

impl<T: fmt::Debug> Stack<T> {
    fn new(capacity: usize) -> Self {
        Self { data: Vec::with_capacity(capacity), capacity }
    }

    fn push(&mut self, item: T) -> Result<(), StackError> {
        if self.data.len() >= self.capacity {
            Err(StackError::Overflow(self.capacity))
        } else {
            self.data.push(item);
            Ok(())
        }
    }

    fn pop(&mut self) -> Result<T, StackError> {
        self.data.pop().ok_or(StackError::Empty)
    }
}

// Trait with a lifetime parameter
trait Summary<'a> {
    fn summarise(&'a self) -> &'a str;
    fn preview(&'a self, max: usize) -> &'a str {
        let s = self.summarise();
        &s[..s.len().min(max)]
    }
}

struct Article<'a> {
    title: &'a str,
    body:  &'a str,
}

impl<'a> Summary<'a> for Article<'a> {
    fn summarise(&'a self) -> &'a str {
        self.title
    }
}

fn print_preview(item: &impl Summary<'_>) {
    println!("Preview: {}", item.preview(40));
}

fn word_count(text: &str) -> HashMap<&str, usize> {
    let mut map = HashMap::new();
    for word in text.split_whitespace() {
        *map.entry(word).or_insert(0) += 1;
    }
    map
}

fn main() {
    let mut stack: Stack<i32> = Stack::new(4);
    for n in [10, 20, 30, 40] {
        stack.push(n).expect("push failed");
    }
    while let Ok(val) = stack.pop() {
        println!("popped: {val}");
    }

    let counts = word_count("the quick brown fox jumps over the lazy fox");
    let mut pairs: Vec<_> = counts.iter().collect();
    pairs.sort_by(|a, b| b.1.cmp(a.1));
    println!("{pairs:#?}");

    let article = Article { title: "Rust lifetimes explained", body: "..." };
    print_preview(&article);
}

CSS Web

/* Design token layer — CSS custom properties */
:root {
  --color-bg:           #0f0f14;
  --color-surface:      #1a1a24;
  --color-border:       rgba(255 255 255 / 0.08);
  --color-text:         #e2e2f0;
  --color-muted:        #9090a8;
  --color-accent:       #7c6bea;
  --color-accent-glow:  rgba(124 107 234 / 0.35);

  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 16px;

  --font-mono:  'JetBrains Mono', monospace;
  --font-sans:  system-ui, sans-serif;
  --font-size:  14px;

  --ease-spring:     cubic-bezier(0.34, 1.56, 0.64, 1);
  --transition-fast: 120ms ease;
}

/* Palette card in the sidebar */
.palette-card {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  padding: 0.75rem 1rem;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  cursor: pointer;
  transition:
    border-color var(--transition-fast),
    box-shadow  var(--transition-fast);
}

.palette-card:hover,
.palette-card.active {
  border-color: var(--color-accent);
  box-shadow: 0 0 0 3px var(--color-accent-glow);
}

/* Colour-swatch strip */
.swatch-row {
  display: flex;
  height: 8px;
  border-radius: var(--radius-sm);
  overflow: hidden;
  gap: 2px;
}

.swatch-row span {
  flex: 1;
  border-radius: 2px;
}

/* Layout grid */
.app-grid {
  display: grid;
  grid-template-columns: var(--sidebar-w) 1fr;
  grid-template-rows: var(--header-h) 1fr;
  grid-template-areas:
    "header header"
    "sidebar main";
  min-height: 100dvh;
}

/* Pseudo-elements */
.palette-card.active::before {
  content: '';
  position: absolute;
  inset: -1px;
  border-radius: inherit;
  background: linear-gradient(135deg, var(--color-accent), transparent);
  opacity: 0.15;
  pointer-events: none;
}

/* Fluid typography with clamp() and calc() */
.code-body {
  font-size: clamp(12px, calc(0.8rem + 0.2vw), 16px);
  line-height: calc(1.5 + 0.1 * (var(--font-size) - 12px));
}

/* Animations */
@keyframes fade-in {
  from { opacity: 0; transform: translateY(4px); }
  to   { opacity: 1; transform: translateY(0); }
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

.code-block {
  animation: fade-in 200ms var(--ease-out) both;
}

.loading-spinner {
  width: 16px;
  height: 16px;
  border: 2px solid var(--color-border);
  border-top-color: var(--color-accent);
  border-radius: 50%;
  animation: spin 600ms linear infinite;
}

/* Responsive sidebar collapse */
@media (max-width: 768px) {
  .sidebar {
    position: fixed;
    inset: auto 0 0;
    z-index: 100;
    border-radius: var(--radius-lg) var(--radius-lg) 0 0;
    transform: translateY(100%);
    transition: transform 300ms var(--ease-spring);
  }

  .sidebar.open {
    transform: translateY(0);
  }
}

Bash Shell

#!/usr/bin/env bash
# deploy.sh — build, test, and sync to S3 with CloudFront invalidation

set -euo pipefail

readonly SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
readonly ENV="${1:-staging}"
readonly BUCKET="my-app-${ENV}"
readonly BUILD_DIR="${SCRIPT_DIR}/dist"

log()  { printf '[%s] %s\n' "$(date +%T)" "$*"; }
die()  { log "ERROR: $*" >&2; exit 1; }

check_deps() {
  local deps=(aws node pnpm)
  for dep in "${deps[@]}"; do
    command -v "$dep" &>/dev/null || die "Missing dependency: $dep"
  done
}

build() {
  log "Building for: $ENV"
  NODE_ENV=production pnpm run build
  [[ -d "$BUILD_DIR" ]] || die "Build output missing at $BUILD_DIR"
  log "Build complete — $(du -sh "$BUILD_DIR" | cut -f1)"
}

deploy() {
  log "Syncing to s3://$BUCKET …"
  aws s3 sync "$BUILD_DIR" "s3://$BUCKET" \
    --delete \
    --cache-control "public,max-age=31536000,immutable" \
    --exclude "index.html"

  # Upload index.html with no-cache so stale CDN copies expire immediately
  aws s3 cp "$BUILD_DIR/index.html" "s3://$BUCKET/index.html" \
    --cache-control "no-cache,no-store,must-revalidate"

  log "Invalidating CloudFront distribution…"
  aws cloudfront create-invalidation \
    --distribution-id "$CF_DIST_ID" \
    --paths '/*' \
    --query 'Invalidation.Id' \
    --output text
}

main() {
  check_deps
  build
  deploy
  log "Deploy to $ENV complete ✓"
}

main "$@"

Go Systems

package main

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"log/slog"
	"net/http"
	"time"
)

type User struct {
	ID        int       `json:"id"`
	Name      string    `json:"name"`
	Email     string    `json:"email"`
	CreatedAt time.Time `json:"created_at"`
}

var ErrNotFound = errors.New("user not found")

type UserService struct {
	baseURL string
	client  *http.Client
}

func NewUserService(baseURL string) *UserService {
	return &UserService{
		baseURL: baseURL,
		client:  &http.Client{Timeout: 10 * time.Second},
	}
}

func (s *UserService) GetUser(ctx context.Context, id int) (*User, error) {
	url := fmt.Sprintf("%s/users/%d", s.baseURL, id)
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
	if err != nil {
		return nil, fmt.Errorf("creating request: %w", err)
	}

	resp, err := s.client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("executing request: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode == http.StatusNotFound {
		return nil, ErrNotFound
	}
	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("unexpected status %d", resp.StatusCode)
	}

	var user User
	if err := json.NewDecoder(resp.Body).Decode(&user); err != nil {
		return nil, fmt.Errorf("decoding response: %w", err)
	}
	return &user, nil
}

// fanOut fetches multiple users concurrently and merges results.
func fanOut(ctx context.Context, svc *UserService, ids []int) []*User {
	type result struct {
		user *User
		err  error
	}
	ch := make(chan result, len(ids))

	for _, id := range ids {
		go func(id int) {
			u, err := svc.GetUser(ctx, id)
			ch <- result{u, err}
		}(id)
	}

	var users []*User
	for range ids {
		select {
		case r := <-ch:
			if r.err == nil {
				users = append(users, r.user)
			}
		case <-ctx.Done():
			return users
		}
	}
	return users
}

func main() {
	svc := NewUserService("https://api.example.com")
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	user, err := svc.GetUser(ctx, 42)
	if errors.Is(err, ErrNotFound) {
		slog.Warn("user not found", "id", 42)
		return
	}
	if err != nil {
		slog.Error("failed to get user", "err", err)
		return
	}
	slog.Info("found user", "name", user.Name, "email", user.Email)

	batch := fanOut(ctx, svc, []int{1, 2, 3, 4, 5})
	slog.Info("batch fetched", "count", len(batch))
}

Java JVM

import java.util.*;
import java.util.concurrent.*;
import java.util.stream.*;

// Record type (Java 16+)
record Point(double x, double y) {
    double distanceTo(Point other) {
        double dx = x - other.x, dy = y - other.y;
        return Math.sqrt(dx * dx + dy * dy);
    }
}

// Sealed interface + switch expression (Java 17+)
sealed interface Shape permits Circle, Rect {}
record Circle(double radius) implements Shape {}
record Rect(double w, double h) implements Shape {}

class Geometry {
    static double area(Shape s) {
        return switch (s) {
            case Circle c -> Math.PI * c.radius() * c.radius();
            case Rect   r -> r.w() * r.h();
        };
    }

    // Text block (Java 15+)
    static final String QUERY = """
            SELECT id, name, email
            FROM users
            WHERE active = true
            ORDER BY name;
            """;
}

/** Generic LRU cache backed by LinkedHashMap. */
public class LRUCache<K, V> extends LinkedHashMap<K, V> {
    private final int capacity;

    public LRUCache(int capacity) {
        super(capacity, 0.75f, true);
        this.capacity = capacity;
    }

    @Override
    protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
        return size() > capacity;
    }

    public static void main(String[] args) throws Exception {
        LRUCache<Integer, String> cache = new LRUCache<>(3);
        cache.put(1, "alpha");
        cache.put(2, "beta");
        cache.put(3, "gamma");
        cache.get(1);           // access moves it to tail
        cache.put(4, "delta");  // evicts 2 (LRU)
        System.out.println(cache.keySet()); // [3, 1, 4]

        // Parallel stream partitioning
        List<Integer> numbers = IntStream.rangeClosed(1, 20)
            .boxed()
            .collect(Collectors.toList());

        Map<Boolean, List<Integer>> parts = numbers.parallelStream()
            .collect(Collectors.partitioningBy(n -> n % 2 == 0));

        System.out.println("Even: " + parts.get(true));
        System.out.println("Odd:  " + parts.get(false));

        // CompletableFuture pipeline
        CompletableFuture.supplyAsync(() -> "Hello")
            .thenApply(s -> s + ", World")
            .thenApply(String::toUpperCase)
            .thenAccept(System.out::println)
            .get(2, TimeUnit.SECONDS);
    }
}

Kotlin JVM

import kotlinx.coroutines.*
import kotlinx.coroutines.flow.*

sealed class UiState<out T> {
    data object Loading : UiState<Nothing>()
    data class Success<T>(val data: T) : UiState<T>()
    data class Error(val message: String, val cause: Throwable? = null) : UiState<Nothing>()
}

data class User(
    val id: Long,
    val name: String,
    val email: String,
    val roles: Set<String> = emptySet(),
) {
    val isAdmin: Boolean get() = "admin" in roles
    fun withRole(role: String) = copy(roles = roles + role)
}

class UserRepository(private val api: UserApi) {
    fun observeUser(id: Long): Flow<UiState<User>> = flow {
        emit(UiState.Loading)
        runCatching { api.fetchUser(id) }
            .onSuccess { emit(UiState.Success(it)) }
            .onFailure { emit(UiState.Error(it.message ?: "Unknown error", it)) }
    }.catch { e ->
        emit(UiState.Error("Stream error: ${e.message}"))
    }
}

fun main() = runBlocking {
    val users = listOf(
        User(1, "Alice", "alice@example.com", setOf("admin", "user")),
        User(2, "Bob",   "bob@example.com"),
        User(3, "Carol", "carol@example.com", setOf("user")),
    )

    users.asFlow()
        .filter { it.isAdmin }
        .map { it.withRole("superadmin") }
        .collect { println(it) }
}

Swift Apple

import Foundation

// Protocol-oriented networking
protocol Endpoint {
    var baseURL: URL { get }
    var path: String { get }
    var method: String { get }
    var headers: [String: String] { get }
}

extension Endpoint {
    var method: String { "GET" }
    var headers: [String: String] { ["Content-Type": "application/json"] }

    func urlRequest() -> URLRequest {
        var request = URLRequest(url: baseURL.appendingPathComponent(path))
        request.httpMethod = method
        headers.forEach { request.setValue($1, forHTTPHeaderField: $0) }
        return request
    }
}

// Codable model
struct Post: Codable, Identifiable {
    let id: Int
    let title: String
    let body: String
    let userId: Int
}

// Generic async fetch
func fetch<T: Decodable>(_ endpoint: some Endpoint) async throws -> T {
    let (data, response) = try await URLSession.shared.data(for: endpoint.urlRequest())
    guard let http = response as? HTTPURLResponse,
          (200..<300).contains(http.statusCode) else {
        throw URLError(.badServerResponse)
    }
    return try JSONDecoder().decode(T.self, from: data)
}

// Result builder — tiny HTML DSL
@resultBuilder
struct HTMLBuilder {
    static func buildBlock(_ parts: String...) -> String {
        parts.joined(separator: "\n")
    }
}

func html(@HTMLBuilder content: () -> String) -> String {
    "<html>\(content())</html>"
}

let page = html {
    "<head><title>Hello</title></head>"
    "<body><p>Swift result builders!</p></body>"
}
print(page)

Ruby Scripting

# frozen_string_literal: true

require 'net/http'
require 'json'
require 'uri'

module Retriable
  MAX_ATTEMPTS = 3

  def with_retry(attempts: MAX_ATTEMPTS, delay: 0.5)
    attempts.times do |i|
      return yield
    rescue => e
      raise if i == attempts - 1
      warn "Retry #{i + 1}/#{attempts - 1}: #{e.message}"
      sleep(delay * 2**i)
    end
  end
end

class ApiClient
  include Retriable

  BASE_URL = 'https://jsonplaceholder.typicode.com'

  def initialize(timeout: 10)
    uri            = URI(BASE_URL)
    @http          = Net::HTTP.new(uri.host, uri.port)
    @http.use_ssl  = true
    @http.read_timeout = timeout
  end

  def get(path)
    with_retry do
      res = @http.get(path, 'Accept' => 'application/json')
      raise "HTTP #{res.code}" unless res.is_a?(Net::HTTPSuccess)
      JSON.parse(res.body, symbolize_names: true)
    end
  end
end

client  = ApiClient.new
posts   = client.get('/posts')
summary = posts
  .group_by { |p| p[:userId] }
  .transform_values(&:count)
  .sort_by { |_, v| -v }

summary.first(5).each do |user_id, count|
  puts "User #{user_id}: #{count} posts"
end

Haskell Functional

module Main where

import Data.List (sortBy)
import Data.Map.Strict (Map)
import qualified Data.Map.Strict as Map
import Data.Ord (Down (..), comparing)

-- Infinite lazy Fibonacci list
fibs :: [Integer]
fibs = 0 : 1 : zipWith (+) fibs (tail fibs)

fibN :: Int -> Integer
fibN = (fibs !!)

-- Word frequency map
frequency :: (Ord a) => [a] -> Map a Int
frequency = foldr (\x -> Map.insertWith (+) x 1) Map.empty

topN :: (Ord a) => Int -> [a] -> [(a, Int)]
topN n =
  take n
    . sortBy (comparing (Down . snd))
    . Map.toList
    . frequency

-- Generic rose tree (BST)
data Tree a = Leaf | Node a (Tree a) (Tree a)
  deriving (Show, Functor)

insert :: (Ord a) => a -> Tree a -> Tree a
insert x Leaf = Node x Leaf Leaf
insert x (Node y l r)
  | x < y     = Node y (insert x l) r
  | x > y     = Node y l (insert x r)
  | otherwise  = Node y l r

toList :: Tree a -> [a]
toList Leaf          = []
toList (Node x l r)  = toList l ++ [x] ++ toList r

treeSort :: (Ord a) => [a] -> [a]
treeSort = toList . foldr insert Leaf

main :: IO ()
main = do
  putStrLn "First 15 Fibonacci numbers:"
  print (take 15 fibs)

  let ws = words "the cat sat on the mat and the cat sat"
  putStrLn "\nTop 3 words:"
  mapM_ print (topN 3 ws)

  putStrLn "\nTree-sorted:"
  print (treeSort [5, 3, 8, 1, 4, 7, 2 :: Int])

SQL Data

-- Monthly revenue by product category with 3-month rolling average
WITH
  monthly_sales AS (
    SELECT
      DATE_TRUNC('month', o.created_at)          AS month,
      p.category,
      SUM(oi.quantity * oi.unit_price)            AS revenue,
      COUNT(DISTINCT o.user_id)                   AS unique_buyers,
      AVG(oi.quantity * oi.unit_price) OVER (
        PARTITION BY p.category
        ORDER BY DATE_TRUNC('month', o.created_at)
        ROWS BETWEEN 2 PRECEDING AND CURRENT ROW
      )                                            AS revenue_3mo_avg
    FROM  orders       o
    JOIN  order_items  oi ON oi.order_id  = o.id
    JOIN  products     p  ON p.id         = oi.product_id
    WHERE
      o.status     = 'completed'
      AND o.created_at >= CURRENT_DATE - INTERVAL '12 months'
    GROUP BY 1, 2
  ),

  ranked AS (
    SELECT
      *,
      RANK() OVER (PARTITION BY month ORDER BY revenue DESC) AS rnk
    FROM monthly_sales
  )

SELECT
  TO_CHAR(month, 'YYYY-MM') AS period,
  category,
  ROUND(revenue, 2)          AS revenue,
  unique_buyers,
  ROUND(revenue_3mo_avg, 2)  AS rolling_avg,
  rnk
FROM  ranked
WHERE rnk <= 5
ORDER BY month DESC, rnk;

HTML Web

<!doctype html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta name="description" content="Syntax — syntax theme browser" />
    <title>Syntax</title>
    <link rel="preconnect" href="https://fonts.googleapis.com" />
    <link
      rel="stylesheet"
      href="https://fonts.googleapis.com/css2?family=JetBrains+Mono:wght@400;500&display=swap"
    />
    <link rel="stylesheet" href="/styles/global.css" />
  </head>
  <body data-palette="dracula">
    <header class="site-header" role="banner">
      <a href="/" class="logo" aria-label="Syntax home">
        <span class="logo-icon" aria-hidden="true">◈</span>
        Syntax
      </a>
      <nav aria-label="Primary navigation">
        <a href="/about">About</a>
        <a href="https://gitlab.com/brennankbrown/syntax" rel="noopener noreferrer">
          GitHub
        </a>
      </nav>
    </header>

    <main class="layout">
      <aside class="sidebar" aria-label="Theme controls">
        <!-- Controls injected by Astro components -->
      </aside>

      <section class="content" aria-label="Code previews">
        <article class="code-block" data-lang="javascript" data-visible="true">
          <header class="code-block__header">
            <span class="lang-badge">JavaScript</span>
            <button class="copy-btn" aria-label="Copy code">Copy</button>
          </header>
          <pre><code><!-- highlighted HTML injected at build time --></code></pre>
        </article>
      </section>
    </main>

    <button
      class="fab-menu"
      aria-label="Open theme controls"
      aria-expanded="false"
    >
      ◈ Themes
    </button>

    <script type="module" src="/scripts/switcher.js"></script>
  </body>
</html>

JSON Web

{
  "$schema": "https://json.schemastore.org/package.json",
  "name": "syntax",
  "version": "1.0.0",
  "description": "Interactive syntax theme and colour palette browser",
  "type": "module",
  "scripts": {
    "dev": "astro dev",
    "build": "astro build",
    "preview": "astro preview",
    "check": "astro check && tsc --noEmit",
    "lint": "eslint src --ext .ts,.astro",
    "format": "prettier --write ."
  },
  "dependencies": {
    "astro": "^4.15.0",
    "shiki": "^1.18.0"
  },
  "devDependencies": {
    "@types/node": "^20.0.0",
    "eslint": "^9.0.0",
    "prettier": "^3.0.0",
    "prettier-plugin-astro": "^0.14.0",
    "typescript": "^5.5.0"
  },
  "engines": {
    "node": ">=18.14.1"
  },
  "keywords": ["syntax", "theme", "shiki", "astro", "colour-palette"],
  "license": "MIT",
  "repository": {
    "type": "git",
    "url": "https://gitlab.com/brennankbrown/syntax"
  },
  "prettier": {
    "singleQuote": true,
    "semi": true,
    "tabWidth": 2,
    "plugins": ["prettier-plugin-astro"]
  }
}

YAML Web

# GitHub Actions — CI/CD pipeline
name: Deploy Syntax

on:
  push:
    branches: [main]
  pull_request:
    branches: [main]

env:
  NODE_VERSION: "20"
  PNPM_VERSION: "9"

jobs:
  build-and-test:
    name: Build & Test
    runs-on: ubuntu-latest
    timeout-minutes: 15

    steps:
      - name: Checkout repository
        uses: actions/checkout@v4

      - name: Set up Node.js
        uses: actions/setup-node@v4
        with:
          node-version: ${{ env.NODE_VERSION }}
          cache: pnpm

      - name: Install pnpm
        run: npm i -g pnpm@${{ env.PNPM_VERSION }}

      - name: Install dependencies
        run: pnpm install --frozen-lockfile

      - name: Type-check
        run: pnpm run check

      - name: Build
        run: pnpm run build

      - name: Upload build artifact
        uses: actions/upload-pages-artifact@v3
        with:
          path: dist/

  deploy:
    name: Deploy to Netlify
    needs: build-and-test
    if: github.ref == 'refs/heads/main'
    runs-on: ubuntu-latest
    environment:
      name: production
      url: ${{ steps.deploy.outputs.deploy-url }}

    steps:
      - name: Deploy
        id: deploy
        uses: netlify/actions/cli@master
        with:
          args: deploy --prod --dir=dist
        env:
          NETLIFY_AUTH_TOKEN: ${{ secrets.NETLIFY_AUTH_TOKEN }}
          NETLIFY_SITE_ID: ${{ secrets.NETLIFY_SITE_ID }}

C++ Systems

#include <algorithm>
#include <iostream>
#include <memory>
#include <optional>
#include <string>
#include <vector>

// CRTP-based mixin for printable types
template <typename Derived>
struct Printable {
    void print() const {
        static_cast<const Derived*>(this)->print_impl(std::cout);
        std::cout << '\n';
    }
};

struct Point : Printable<Point> {
    double x, y;
    void print_impl(std::ostream& os) const {
        os << "Point(" << x << ", " << y << ")";
    }
    double dist(const Point& o) const {
        double dx = x - o.x, dy = y - o.y;
        return std::sqrt(dx * dx + dy * dy);
    }
};

// Generic min-heap priority queue wrapper
template <typename T, typename Cmp = std::less<T>>
class Heap {
    std::vector<T> data_;
    Cmp cmp_;
public:
    void push(T val) {
        data_.push_back(std::move(val));
        std::push_heap(data_.begin(), data_.end(), cmp_);
    }
    T pop() {
        std::pop_heap(data_.begin(), data_.end(), cmp_);
        T top = std::move(data_.back());
        data_.pop_back();
        return top;
    }
    [[nodiscard]] bool empty() const noexcept { return data_.empty(); }
    [[nodiscard]] std::size_t size() const noexcept { return data_.size(); }
};

// constexpr — compile-time factorial
constexpr unsigned long long factorial(unsigned n) noexcept {
    return n <= 1 ? 1 : n * factorial(n - 1);
}

// std::optional — safe lookup
std::optional<int> findFirst(const std::vector<int>& v, int target) {
    for (const auto& x : v)
        if (x == target) return x;
    return std::nullopt;
}

int main() {
    Point a{0.0, 0.0}, b{3.0, 4.0};
    a.print();
    std::cout << "Distance: " << a.dist(b) << '\n';

    // Smart pointer ownership
    auto heap = std::make_unique<Heap<int, std::greater<int>>>();
    for (int v : {5, 1, 8, 3, 9, 2}) heap->push(v);

    std::cout << "Sorted: ";
    while (!heap->empty())
        std::cout << heap->pop() << ' ';
    std::cout << '\n';

    // Structured bindings + optional
    std::vector<std::pair<std::string, int>> scores{{"Alice", 95}, {"Bob", 82}};
    for (const auto& [name, score] : scores)
        std::cout << name << ": " << score << '\n';

    constexpr auto fact10 = factorial(10);
    std::cout << "10! = " << fact10 << '\n';

    if (auto val = findFirst({1, 2, 3, 4}, 3); val.has_value())
        std::cout << "Found: " << *val << '\n';
}

Zig Systems

const std = @import("std");
const Allocator = std.mem.Allocator;

// Generic stack backed by ArrayList
fn Stack(comptime T: type) type {
    return struct {
        const Self = @This();

        items: std.ArrayList(T),

        pub fn init(alloc: Allocator) Self {
            return .{ .items = std.ArrayList(T).init(alloc) };
        }

        pub fn deinit(self: *Self) void {
            self.items.deinit();
        }

        pub fn push(self: *Self, val: T) !void {
            try self.items.append(val);
        }

        pub fn pop(self: *Self) ?T {
            return if (self.items.items.len == 0)
                null
            else
                self.items.pop();
        }

        pub fn len(self: Self) usize {
            return self.items.items.len;
        }
    };
}

// Comptime string interning
fn comptimeUpper(comptime s: []const u8) []const u8 {
    comptime {
        var buf: [s.len]u8 = undefined;
        for (s, 0..) |c, i| buf[i] = std.ascii.toUpper(c);
        return buf[0..];
    }
}

pub fn main() !void {
    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
    defer _ = gpa.deinit();
    const alloc = gpa.allocator();

    var stack = Stack(i32).init(alloc);
    defer stack.deinit();

    for ([_]i32{ 10, 20, 30, 40, 50 }) |v| try stack.push(v);

    const stdout = std.io.getStdOut().writer();
    while (stack.pop()) |v| {
        try stdout.print("popped: {d}\n", .{v});
    }

    const msg = comptimeUpper("chromacode");
    try stdout.print("Comptime: {s}\n", .{msg});
}

C# .NET

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace Syntax.Examples;

// Record types for immutable models
public record User(int Id, string Name, string Email, Role Role = Role.User)
{
    public bool IsAdmin => Role == Role.Admin;
}

public enum Role { Guest, User, Admin }

// Generic result monad
public readonly struct Result<T>
{
    private readonly T? _value;
    private readonly string? _error;

    private Result(T value) { _value = value; _error = null; }
    private Result(string error) { _value = default; _error = error; }

    public static Result<T> Ok(T value)    => new(value);
    public static Result<T> Fail(string e) => new(e);

    public bool IsOk => _error is null;
    public T Value   => IsOk ? _value! : throw new InvalidOperationException(_error);

    public Result<U> Map<U>(Func<T, U> f) =>
        IsOk ? Result<U>.Ok(f(_value!)) : Result<U>.Fail(_error!);
}

// Async user service with LINQ projections
public class UserService(IEnumerable<User> seed)
{
    private readonly List<User> _store = [.. seed];

    public Task<Result<User>> FindAsync(int id) =>
        Task.FromResult(
            _store.FirstOrDefault(u => u.Id == id) is { } u
                ? Result<User>.Ok(u)
                : Result<User>.Fail($"User {id} not found"));

    public IEnumerable<string> AdminNames() =>
        _store.Where(u => u.IsAdmin).Select(u => u.Name).Order();
}

class Program
{
    static async Task Main()
    {
        var svc = new UserService([
            new(1, "Alice", "alice@example.com", Role.Admin),
            new(2, "Bob",   "bob@example.com"),
            new(3, "Carol", "carol@example.com", Role.Admin),
        ]);

        var result = await svc.FindAsync(1);
        if (result.IsOk)
            Console.WriteLine($"Found: {result.Value.Name}");

        Console.WriteLine("Admins: " + string.Join(", ", svc.AdminNames()));
    }
}

Scala JVM

import scala.concurrent.{ExecutionContext, Future}
import scala.util.{Failure, Success}

// ADT via sealed trait + case classes
sealed trait Shape {
  def area: Double
  def perimeter: Double
  override def toString: String = s"${getClass.getSimpleName}(area=${area.round})"
}

case class Circle(radius: Double) extends Shape {
  def area: Double      = math.Pi * radius * radius
  def perimeter: Double = 2 * math.Pi * radius
}

case class Rect(width: Double, height: Double) extends Shape {
  def area: Double      = width * height
  def perimeter: Double = 2 * (width + height)
}

case class Triangle(a: Double, b: Double, c: Double) extends Shape {
  def area: Double = {
    val s = (a + b + c) / 2
    math.sqrt(s * (s - a) * (s - b) * (s - c))
  }
  def perimeter: Double = a + b + c
}

// Typeclass pattern
trait Describable[A] {
  def describe(a: A): String
}

given Describable[Shape] with
  def describe(s: Shape): String = s match
    case Circle(r)      => s"Circle with radius $r"
    case Rect(w, h)     => s"Rectangle ${w}×${h}"
    case Triangle(a, b, c) => s"Triangle sides $a/$b/$c"

def describe[A](a: A)(using d: Describable[A]): String = d.describe(a)

@main def run(): Unit =
  val shapes: List[Shape] = List(Circle(5), Rect(4, 6), Triangle(3, 4, 5))

  shapes
    .sortBy(_.area)
    .foreach(s => println(s"${describe(s)} — area: ${f"${s.area}%.2f"}"))

  val totalArea = shapes.map(_.area).sum
  println(s"Total area: ${f"$totalArea%.2f"}")

PHP Web

<?php

declare(strict_types=1);

namespace App\Http;

use InvalidArgumentException;
use JsonException;

// Typed enums (PHP 8.1+)
enum HttpMethod: string
{
    case GET    = 'GET';
    case POST   = 'POST';
    case PUT    = 'PUT';
    case DELETE = 'DELETE';
}

// Readonly class (PHP 8.2+)
readonly class Request
{
    public function __construct(
        public readonly HttpMethod $method,
        public readonly string     $path,
        public readonly array      $headers = [],
        public readonly ?string    $body    = null,
    ) {}

    public function json(): array
    {
        if ($this->body === null) {
            throw new InvalidArgumentException('Request has no body');
        }
        return json_decode($this->body, true, flags: JSON_THROW_ON_ERROR);
    }
}

// Simple router with first-class callable syntax
class Router
{
    /** @var array<string, array<string, callable>> */
    private array $routes = [];

    public function add(HttpMethod $method, string $path, callable $handler): void
    {
        $this->routes[$method->value][$path] = $handler;
    }

    public function dispatch(Request $req): string
    {
        $handler = $this->routes[$req->method->value][$req->path]
            ?? fn() => throw new InvalidArgumentException("404 {$req->path}");

        return $handler($req);
    }
}

$router = new Router();

$router->add(HttpMethod::GET, '/health', fn(Request $r) => json_encode(['ok' => true]));

$router->add(HttpMethod::POST, '/echo', function (Request $r): string {
    $data = $r->json();
    return json_encode(['echo' => $data], JSON_PRETTY_PRINT);
});

$request = new Request(HttpMethod::POST, '/echo', body: '{"hello":"world"}');
echo $router->dispatch($request) . PHP_EOL;

GraphQL Web

"""A syntax palette available in Syntax."""
type Palette {
  id:          ID!
  name:        String!
  mode:        ColourMode!
  shikiTheme:  String!
  swatchColors: [String!]!
}

"""A monospace typeface available for preview."""
type Font {
  id:         ID!
  name:       String!
  googleSlug: String!
}

"""A language code sample."""
type Language {
  id:             ID!
  label:          String!
  shikiLang:      String!
  group:          String!
  defaultVisible: Boolean!
}

enum ColourMode { DARK LIGHT }

type Query {
  """Retrieve all palettes, optionally filtered by mode."""
  palettes(mode: ColourMode): [Palette!]!

  """Look up a single palette by its ID."""
  palette(id: ID!): Palette

  """Retrieve all available fonts."""
  fonts: [Font!]!

  """Retrieve all language samples, optionally by group."""
  languages(group: String): [Language!]!
}

type Mutation {
  """Record a palette view event for analytics."""
  recordView(paletteId: ID!, langId: ID!): Boolean!
}

# Example operation
query GetDarkPalettes {
  palettes(mode: DARK) {
    id
    name
    swatchColors
  }
}

fragment PaletteFields on Palette {
  id
  name
  mode
  shikiTheme
}

Elixir Functional

defmodule Syntax.Pipeline do
  @moduledoc """
  Demonstrates Elixir's pipe operator, pattern matching,
  structs, and Stream-based lazy processing.
  """

  defstruct [:name, :email, role: :user]

  @type t :: %__MODULE__{
    name:  String.t(),
    email: String.t(),
    role:  :user | :admin | :guest,
  }

  # Pattern-matched guard clauses
  def greet(%__MODULE__{role: :admin, name: name}), do: "Welcome back, admin #{name}!"
  def greet(%__MODULE__{name: name}),               do: "Hello, #{name}."

  # Pipe-heavy data transformation
  def top_words(text, n \\ 5) do
    text
    |> String.downcase()
    |> String.split(~r/\W+/, trim: true)
    |> Enum.frequencies()
    |> Enum.sort_by(fn {_k, v} -> -v end)
    |> Enum.take(n)
    |> Enum.map(fn {word, count} -> "#{word}: #{count}" end)
  end

  # Lazy stream — only computes what's needed
  def fib_stream do
    Stream.unfold({0, 1}, fn {a, b} -> {a, {b, a + b}} end)
  end

  def first_fibs(n), do: fib_stream() |> Enum.take(n)
end

alias Syntax.Pipeline

alice = %Pipeline{name: "Alice", email: "alice@example.com", role: :admin}
bob   = %Pipeline{name: "Bob",   email: "bob@example.com"}

IO.puts Pipeline.greet(alice)
IO.puts Pipeline.greet(bob)

sample = "the quick brown fox jumps over the lazy fox and the lazy dog"
Pipeline.top_words(sample, 3) |> Enum.each(&IO.puts/1)

Pipeline.first_fibs(10) |> IO.inspect(label: "Fibonacci")

Lua Scripting

-- Prototype-based OOP in Lua
local Vector = {}
Vector.__index = Vector

function Vector.new(x, y)
  return setmetatable({ x = x, y = y }, Vector)
end

function Vector:__add(other)  return Vector.new(self.x + other.x, self.y + other.y) end
function Vector:__sub(other)  return Vector.new(self.x - other.x, self.y - other.y) end
function Vector:__mul(scalar) return Vector.new(self.x * scalar,  self.y * scalar)  end
function Vector:__eq(other)   return self.x == other.x and self.y == other.y        end

function Vector:len()   return math.sqrt(self.x^2 + self.y^2) end
function Vector:norm()  return self * (1 / self:len())         end
function Vector:dot(v)  return self.x * v.x + self.y * v.y    end

function Vector:__tostring()
  return string.format("Vector(%.2f, %.2f)", self.x, self.y)
end

-- Coroutine-based range iterator
local function range(from, to, step)
  step = step or 1
  return coroutine.wrap(function()
    for i = from, to, step do
      coroutine.yield(i)
    end
  end)
end

-- Functional helpers
local function map(t, f)
  local out = {}
  for i, v in ipairs(t) do out[i] = f(v) end
  return out
end

local function filter(t, pred)
  local out = {}
  for _, v in ipairs(t) do
    if pred(v) then out[#out + 1] = v end
  end
  return out
end

local v1 = Vector.new(3, 4)
local v2 = Vector.new(1, 2)

print(tostring(v1))
print("Length:", v1:len())
print("Normalised:", tostring(v1:norm()))
print("Dot product:", v1:dot(v2))
print("Sum:", tostring(v1 + v2))

local nums = {}
for n in range(1, 20) do nums[#nums + 1] = n end
local evens  = filter(nums, function(n) return n % 2 == 0 end)
local squares = map(evens, function(n) return n * n end)
print("Even squares:", table.concat(squares, ", "))

TOML Data

# Syntax project configuration
[project]
name        = "syntax"
version     = "1.0.0"
description = "Interactive syntax theme & font browser"
license     = "AGPL-3.0-only"
authors     = ["Brennan Kenneth Brown <hi@brennan.day>"]
repository  = "https://gitlab.com/brennankbrown/syntax"

[project.keywords]
tags = ["syntax", "theme", "shiki", "astro", "colour"]

[build]
framework   = "astro"
output      = "static"
dist        = "dist/"
node        = ">=18.14.1"
typescript  = "strict"

[deploy]
provider    = "netlify"
branch      = "main"
auto_deploy = true

  [deploy.headers]
  "Cache-Control"             = "public, max-age=31536000, immutable"
  "X-Content-Type-Options"    = "nosniff"
  "X-Frame-Options"           = "DENY"
  "Referrer-Policy"           = "strict-origin-when-cross-origin"

[[palettes]]
id    = "dracula"
name  = "Dracula"
mode  = "dark"
theme = "dracula"

[[palettes]]
id    = "catppuccin-mocha"
name  = "Catppuccin Mocha"
mode  = "dark"
theme = "catppuccin-mocha"

[[palettes]]
id    = "catppuccin-latte"
name  = "Catppuccin Latte"
mode  = "light"
theme = "catppuccin-latte"

[features]
palette_switching = true
font_switching    = true
language_filter   = true
keyboard_nav      = true
mobile_sidebar    = true

Dockerfile DevOps

# syntax=docker/dockerfile:1
# Multi-stage build for a Node.js / Astro static site

# ── Stage 1: dependencies ──────────────────────────────────
FROM node:20-alpine AS deps
WORKDIR /app

RUN corepack enable && corepack prepare pnpm@latest --activate

COPY package.json pnpm-lock.yaml ./
RUN pnpm install --frozen-lockfile

# ── Stage 2: build ────────────────────────────────────────
FROM node:20-alpine AS build
WORKDIR /app

COPY --from=deps /app/node_modules ./node_modules
COPY . .

ENV NODE_ENV=production
RUN pnpm run build

# ── Stage 3: serve ────────────────────────────────────────
FROM nginx:1.27-alpine AS serve

LABEL org.opencontainers.image.title="Syntax"
LABEL org.opencontainers.image.source="https://gitlab.com/brennankbrown/syntax"
LABEL org.opencontainers.image.licenses="AGPL-3.0-only"

COPY --from=build /app/dist /usr/share/nginx/html
COPY docker/nginx.conf       /etc/nginx/conf.d/default.conf

RUN addgroup -S app && adduser -S app -G app \
 && chown -R app:app /usr/share/nginx/html \
 && chmod -R 755 /usr/share/nginx/html

EXPOSE 8080

HEALTHCHECK --interval=30s --timeout=5s --start-period=5s --retries=3 \
  CMD wget -qO- http://localhost:8080/ || exit 1

USER app
CMD ["nginx", "-g", "daemon off;"]

Markdown Data

# Syntax — Markdown Sample

> **Markdown** is a lightweight markup language for creating formatted text using a plain-text editor.
> It was created by John Gruber and Aaron Swartz in 2004.

---

## Text Formatting

Plain paragraph with **bold text**, *italic text*, ~~strikethrough~~, and `inline code`.  
You can also combine them: ***bold and italic***, **_nested styles_**, and `**code**`.

A soft break ends with two spaces.  
This continues on the next line.

---

## Headings

# H1 — Document Title
## H2 — Section
### H3 — Subsection
#### H4 — Detail

---

## Lists

**Unordered:**
- Syntax highlighting
- Font selection
  - Monospace fonts
  - Variable-width fallback
- Theme browsing
  - Dark palettes
  - Light palettes

**Ordered:**
1. Pick a palette
2. Choose a language
3. Adjust the font and size
4. Copy a snippet

**Task list:**
- [x] Dark mode support
- [x] Keyboard navigation
- [x] Copy-to-clipboard
- [ ] Export as image
- [ ] Custom user themes

---

## Blockquotes

> "Any fool can write code that a computer can understand.
> Good programmers write code that humans can understand."
>
> — *Martin Fowler*

> Nested blockquotes:
>
> > This is a second level.
> >
> > > And a third.

---

## Code

Inline: use `const x = 42;` or reference a file with `src/data/palettes.ts`.

Fenced block (TypeScript):

```typescript
interface Palette {
  id:          string;
  name:        string;
  mode:        'dark' | 'light';
  shikiTheme:  string;
  swatchColors: string[];
}

const dracula: Palette = {
  id:          'dracula',
  name:        'Dracula',
  mode:        'dark',
  shikiTheme:  'dracula',
  swatchColors: ['#282a36', '#ff79c6', '#50fa7b', '#f1fa8c', '#8be9fd', '#bd93f9'],
};
```

Shell:

```bash
npm install && npm run build
```

---

## Tables

| Theme              | Mode  | Background | Accent     |
| :----------------- | :---: | ---------: | ---------- |
| Dracula            | dark  | `#282a36`  | `#bd93f9`  |
| Tokyo Night        | dark  | `#1a1b26`  | `#bb9af7`  |
| Catppuccin Latte   | light | `#eff1f5`  | `#8839ef`  |
| Rosé Pine Dawn     | light | `#faf4ed`  | `#907aa9`  |

---

## Links & Images

[Syntax on GitLab](https://gitlab.com/brennankbrown/syntax)  
[🍓 Berry House](https://berryhouse.ca "Berry House homepage")  
[Brennan Kenneth Brown](https://brennan.day)

Reference-style: [Shiki][shiki-url]

[shiki-url]: https://shiki.style "Shiki syntax highlighter"

---

## Horizontal Rules

Three or more hyphens, asterisks, or underscores:

---
***
___

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## HTML in Markdown

<details>
<summary>Click to expand</summary>

This content is **hidden** by default.  
It supports _Markdown_ inside HTML blocks.

</details>

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---

## Footnotes

Syntax uses Shiki for syntax highlighting[^1] and Astro for static site generation[^2].

[^1]: [Shiki](https://shiki.style) is a beautiful syntax highlighter powered by TextMate grammars.
[^2]: [Astro](https://astro.build) builds fast content-driven websites with any JS framework.