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#php
#kotlin
#bash
#go
#sql
#rust
#typescript
#html
#java
#python
#files
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Python
take / drop / takewhile
Take the first N items of an iterable (or while a predicate holds). drop is the complement. Lazy via islice + itertools.dropwhile — works on infinite generators.
@admin
Go
Read File — Whole / Lines / Bytes
Three common patterns: load it all (`os.ReadFile`), iterate line-by-line with `bufio.Scanner`, or stream chunks via `io.Reader`. Pick by file size.
Java
Optional Chains — flatMap, filter
`flatMap` lets you chain Optional-returning methods without nested `if`. `filter` short-circuits to empty if the predicate fails. The functional equivalent of safe-navigation `?.`.
SQL
Views and Materialized Views
A view is a named query — no data stored. A materialized view caches the result; refresh it on demand. Great for expensive joins or aggregations that don't need to be real-time.
Kotlin
fold and scan
`fold` accumulates from a seed across all items. `runningFold` / `scan` yields every intermediate accumulator value — running totals, cumulative metrics.
Bash
Sort by a Specific Column
Sort takes -k for column-based ordering and -t to set the delimiter. -h sorts human-readable sizes ("1.5G", "300K") correctly.
Bash
Find Largest Files and Directories
Quick "where did all my disk go?" answer. du sorts by size, ncdu (interactive) is better for exploration.
SQL
EXISTS vs IN — Subquery Filtering
Both check membership. `EXISTS` is usually faster for big subqueries (stops at first hit). `IN` is more readable for small fixed lists. `NOT IN` is dangerous with NULLs — prefer `NOT EXISTS`.
Kotlin
Cheatsheet: let / apply / also / run / with
Five scope functions cover ~95% of "do something with x" patterns. Pick by two axes: receiver (this vs it) and return value (object itself vs block result).
HTML
Comment / Review Markup with Schema
Comments and reviews can also have Schema.org markup. The `Review` type appears under products in Google search results with star ratings; `Comment` is for general user feedback.
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.
Java
Immutable Collections — List.of / Map.of
Java 9+ static factory methods return immutable collections with no nulls allowed. Concise, fast, and safer to share across threads or APIs than mutable equivalents.
Python
Literal + match for Exhaustive Switching
`Literal` pins a value to specific strings/ints. Combine with the match statement (Python 3.10+) and a `_ : assert_never` clause for exhaustiveness — every variant must be handled or mypy yells at you.
PHP
URL-Safe Base64 Encode / Decode
Standard base64 uses + and / which break in URLs. Swap them for - and _, drop the = padding, and you get a string you can put in path segments and query parameters safely.
Kotlin
Compose Layout: Column, Row, Box
Compose's three fundamental layouts. `Column` stacks vertically, `Row` horizontally, `Box` overlays. Combine with `Modifier.weight()`, alignment, and arrangement for flexible UIs.
Go
time.Since — Easy Benchmark Timing
`time.Since(start)` is shorthand for `time.Now().Sub(start)`. Pair with `defer` for a quick "how long did this function take?" measurement.
SQL
UUID Primary Keys
UUIDs as PKs avoid sequence contention across services and let clients generate IDs offline. v4 is random (worst for B-tree indexes); v7 is time-ordered (B-tree friendly).