Tags
#php
#kotlin
#bash
#go
#sql
#rust
#typescript
#html
#java
#python
#files
#utils
#strings
#http
#concurrency
#async
#json
#arrays
#security
#types
#crypto
#database
#dates
#format
Rust
match with Guards, Ranges, and Bindings
`match` arms can have `if` guards, range patterns (`1..=5`), bindings (`x @ pattern`), and ORs (`A | B`). Combine them for very expressive dispatch.
@admin
Rust
Read a File — Whole / Lines / Bytes
Three common patterns: load it all into memory, iterate line-by-line, or stream bytes. Pick by file size — `read_to_string` is convenient but bad for huge files.
Rust
Untyped JSON with serde_json::Value
When you don't know the JSON shape up-front, parse into `serde_json::Value` and navigate via index / get(). Type-safe pattern matching converts back to Rust types.
SQL
RETURNING — Get Back What You Wrote
PostgreSQL `RETURNING *` returns the rows affected by an INSERT/UPDATE/DELETE — no separate SELECT round-trip needed. SQL Server has `OUTPUT`; MySQL added `RETURNING` in MariaDB and 8.0.31+.
SQL
CREATE TABLE with Constraints
Declare data integrity rules right in the schema — primary keys, foreign keys, unique constraints, NOT NULL, CHECK constraints, defaults. The DB enforces them so application bugs can't corrupt your data.
Kotlin
Result Type — Safe Error-Returning APIs
`Result<T>` wraps "success or thrown exception" without forcing the caller into try/catch. `runCatching { ... }` is the standard producer.
Kotlin
kotlin.test — Basic Tests
`kotlin.test` is the multiplatform test stdlib. `@Test` marks a test; `assertEquals`, `assertTrue`, `assertFailsWith` are the workhorses.
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).
Bash
Get Public IP Address
Several free services return your public IP as plain text. Useful when scripts running behind NAT need to know what address the outside world sees.
Bash
Read File Line-By-Line (the safe way)
The classic `for line in $(cat file)` is wrong — it word-splits and globbing fires on filenames. Use `while IFS= read -r line` with input redirection.
Rust
windows / chunks — Sliding & Fixed
`windows(n)` yields every overlapping sub-slice of length n; `chunks(n)` yields non-overlapping chunks. Both work on slices for free, no extra crates.
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).
Kotlin
lazy — Lazily Computed val
`by lazy { ... }` runs the block on first access, caches the result. Default mode is thread-safe (synchronized). Perfect for expensive initialization where you might never need the value.
Kotlin
Sealed Interfaces (Kotlin 1.5+)
Like sealed classes, but for interfaces — and a class can implement multiple sealed interfaces. Cleaner state modeling when you want "this is both a Loadable and a Cacheable".
Rust
String vs &str — The Cheat Sheet
`String` is an owned, growable heap allocation; `&str` is a borrowed view into a UTF-8 buffer. Function params should usually take `&str`; return types use `String` when ownership is needed.
JavaScript
Random Hex Color
Generates a random 6-digit hex colour string. Useful for seeding avatar backgrounds, chart series colours, placeholder UI elements, and testing colour-dependent components. The crypto version produces a more unpredictable result suitable for generating unique palette tokens.
JavaScript
Promise All with Concurrency Limit
Runs an array of async tasks with a maximum concurrency cap, preventing you from firing hundreds of requests simultaneously. Processes items in batches, moving to the next as slots free up. Essential when hitting rate-limited APIs or processing large datasets without overwhelming the server.