SQL

Gap Detection — Missing Days / Sequences

Find holes in a series — missing invoice numbers, days with no events, gaps in a sequence. Combine `LAG` (or `generate_series`) with a join to spot them.

5h ago 0

Rust

Arc<Mutex<T>> — Shared Mutable State

Share mutable data across threads: `Arc` for the shared ownership, `Mutex` for the synchronized access. Lock with `.lock().unwrap()`; the guard drops the lock on scope exit.

5h ago 0

HTML

Figure + Figcaption (Images, Code, Charts)

`<figure>` groups self-contained illustrative content with its caption. Use it for images, code blocks, charts, diagrams — anything that's referenced from the surrounding text but stands on its own.

5h ago 0

Kotlin

also — Side Effect, Return Itself

`x.also { ... }` runs a side-effect block with `x` as `it` and returns `x` unchanged. Used for logging, debugging, or asserting mid-chain without breaking it.

5h ago 0

SQL

Moving Average (Window Frame)

Add a frame clause (`ROWS BETWEEN N PRECEDING AND CURRENT ROW`) to compute moving averages, sliding sums, rolling stats — anything that needs a bounded look-back.

5h ago 0

Rust

zip / enumerate / chain

Three adapters that pair, index, and concatenate iterators. Every Rust developer reaches for them daily.

5h ago 0

Kotlin

Custom Property Delegate

Any object with `getValue` / `setValue` operator methods can serve as a delegate. Lets you encapsulate cross-cutting behavior (logging, persistence, validation).

5h ago 0

Bash

PID File Management

Write a daemon's PID to a file at start, check on subsequent runs, clean up on exit. Avoids two copies of the same daemon when the script is invoked twice.

5h ago 0

Bash

Run on Multiple Hosts via SSH (with progress)

Iterate a host list, run the same command on each, show colored OK/FAIL summary at the end. Useful for ad-hoc fleet operations without setting up Ansible.

5h ago 0

Go

goroutine + sync.WaitGroup

`go fn()` spawns a goroutine. To wait for several to finish, use `sync.WaitGroup` — call `Add` before spawning, `Done` (deferred) inside, `Wait` to block until all are done.

5h ago 0

HTML

Sortable Table (semantic markup + JS hook)

Use `<button>` inside `<th>` and `aria-sort` on the column so screen readers announce sort state. The button is the keyboard-accessible trigger; JS only handles the actual sort.

5h ago 0

PHP

CSV Writer with Proper Escaping

Write rows to a CSV file using fputcsv with sensible quoting. Also writes a UTF-8 BOM so Excel opens the file with the right encoding.

5h ago 0

Kotlin

Local Functions

Functions can be declared inside other functions. Closures over outer scope let you eliminate parameter-threading. Use sparingly — too many nested locals hurts readability.

5h ago 0

Bash

Parse --flag=value Arguments

A getopts-free arg parser handling long flags, equals-separated values, and bundled short flags. Customize as needed.

5h ago 0

TypeScript

useDebounce — Debounced State

A React hook that returns a debounced version of any value. Trigger expensive effects (search, autosave, network fetches) on this value instead of the raw input.

5h ago 0

Kotlin

Default Arguments + Named Parameters

Default values eliminate most overload sets. Named args make call sites self-documenting and let you skip middle parameters without thinking about positions.

5h ago 0

Bash

Most-Modified Files in Repo

Find the hottest files in a git history — useful for spotting hotspots that need refactoring or extra test coverage.

5h ago 0

TypeScript

useFetch — Minimal Data Fetching Hook

A tiny self-contained data-fetching hook with loading/error/data states and AbortController cleanup on unmount. Good baseline before reaching for TanStack Query.

5h ago 0

Rust

Trait with Default Methods

A trait can supply default implementations — implementors override only the bits they need. Like abstract base classes, but with structural typing and zero runtime cost.

5h ago 0

HTML

Visually Hidden Utility (.sr-only)

Hides content from sighted users but keeps it discoverable by screen readers. Use for icon-only buttons, table-row context, and form-status announcements that don't need visible text.

5h ago 0

JavaScript

JSON Fetch Wrapper

A thin wrapper around fetch that automatically serialises the request body to JSON, sets the Content-Type header, parses the response as JSON, and throws a descriptive error on non-OK responses. Covers the boilerplate needed for 95% of REST API calls in a single reusable function.

5h ago 0

Go

Multiple Return Values + Named Returns

Go functions can return multiple values — most idiomatically a `(result, error)` pair. Named returns let you document the meaning of each value AND enable naked returns in short functions.

5h ago 0

Rust

Custom Iterator Implementation

Implementing `Iterator` is just supplying a `next() -> Option<Item>`. You automatically gain `map`, `filter`, `collect`, and every other adapter for free.

5h ago 0

SQL

ARRAY_AGG and JSON_AGG (PostgreSQL)

Roll up grouped rows into a PostgreSQL array or JSON array — often a faster replacement for the application doing the same "group children under parent" join.

5h ago 0

Bash

Print a Boxed Banner

Wrap a string in a Unicode box for important headers. Auto-sizes to the longest line. Helps milestone messages stand out in long CI logs.

5h ago 0

Kotlin

repeat, also lateinit and isInitialized

`repeat(n) { i -> ... }` for N-times loops where you don't care about index naming. `lateinit var` lets you declare a non-null var without initializing it — common for DI / framework injection.

5h ago 0

Bash

Confirm Prompt (y/n)

A reusable yes/no prompt with a configurable default and a single-keystroke read. Returns 0 for yes, non-zero for no.

5h ago 0

Kotlin

observable — Listen for Property Changes

`Delegates.observable(initial) { prop, old, new -> ... }` fires a callback every time the property changes. Useful for state-tracking, simple observability without a full reactive lib.

5h ago 0

Bash

Run Command with Timeout

`timeout` (GNU coreutils) kills a command after N seconds. Returns exit code 124 on timeout — let the caller distinguish "timed out" from "failed for other reasons."

5h ago 0

Python

pathlib Quick Reference

Forget os.path.* — pathlib.Path is the modern, OS-aware way to work with paths. Operator overloading for joins, attribute access for components, methods for reads/writes/iterations.

5h ago 0