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#php
#kotlin
#bash
#go
#sql
#rust
#typescript
#html
#java
#python
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#async
#json
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#types
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#format
SQL
Pivot Without PIVOT (Conditional Aggregation)
Most databases don't have a real `PIVOT` keyword (SQL Server does). The portable answer is conditional aggregation — `SUM(CASE WHEN ...) AS col` for each pivoted value.
@admin
HTML
Video Element with Captions
`<video>` with multiple `<source>` formats (MP4 + WebM), `controls`, `poster`, and a captions track via `<track kind="captions">`. All shipped with the browser — no JS player needed.
Rust
Async/Await with tokio
`async fn` returns a future; `.await` drives it. tokio is the de-facto runtime. The `#[tokio::main]` attribute turns `main` into the runtime entry point.
Kotlin
with — Scope an Existing Object
`with(x) { ... }` is `run` flipped: the receiver is the first argument. Reads naturally when you're doing several things to an existing object without chaining.
Python
Context Manager via @contextmanager
Build a custom context manager without writing a class — just a generator with one `yield`. The code before yield runs on enter, after yield runs on exit (even on exception).
Rust
From / Into Conversions
Implement `From` and you get `Into` for free. Then `.into()` and `T::from(x)` both work. The single most idiomatic way to express type conversions in Rust.
Kotlin
kotlin.test — Basic Tests
`kotlin.test` is the multiplatform test stdlib. `@Test` marks a test; `assertEquals`, `assertTrue`, `assertFailsWith` are the workhorses.
PHP
Average / Median / Mode
Three classic descriptive statistics over a numeric array. Built without any external math library — just sort + count.
Rust
Serde — Derive Serialize / Deserialize
`#[derive(Serialize, Deserialize)]` is the one-liner that bridges Rust structs and JSON / YAML / TOML / etc. via serde's data-format crates.
SQL
FIRST_VALUE / LAST_VALUE
Return the first or last value within a window. Useful for "compare each row to the partition's first/last value" — for example, "how much have we grown since the user's first order?"
Python
asyncio.to_thread — Run Blocking Code
Wrap a blocking function so it doesn't freeze the event loop. asyncio.to_thread (3.9+) schedules the call onto the default executor and awaits the result.
Java
AtomicInteger / LongAdder
Lock-free atomics for shared counters. `AtomicInteger` for low contention; `LongAdder` for high contention (shards internally — much faster under heavy parallel load).
Kotlin
Ktor Client — POST JSON with Serialization
Combine Ktor + kotlinx.serialization: register the JSON plugin, declare `@Serializable` data classes, the client (de)serializes automatically.
Rust
reqwest GET + JSON Deserialize
`reqwest` is the standard HTTP client. Combined with serde, you can fetch and parse a JSON API response into a typed struct in three lines.
Python
pairwise — Rolling Pair Iterator
`pairwise([a, b, c, d])` yields `(a, b), (b, c), (c, d)` — built into itertools since 3.10. Perfect for "diff consecutive elements" patterns (deltas, rate-of-change, validation between rows).
SQL
Sessionization — Group Events into Sessions
Stitch a stream of events into "sessions" where events more than N minutes apart start a new session. Uses LAG + a SUM-OVER trick to assign session IDs.
PHP
Validate Hex Color
Accept #RGB, #RGBA, #RRGGBB, or #RRGGBBAA hex colors (with or without the leading #). Returns the normalized 6/8-digit lowercase form.