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
Result Combinators + the ? Operator
`Result<T, E>` chains like `Option`. The `?` operator unwraps `Ok` or early-returns the `Err`, converting via `From` so callers can use one error type for many sources.
@admin
HTML
Responsive Image — srcset + sizes
Let the browser pick the right image for the viewport. `srcset` lists candidates by intrinsic width; `sizes` tells the browser how big the image will render. Cuts mobile data dramatically.
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.
SQL
STRING_AGG / GROUP_CONCAT
Concatenate values across a group into a single delimited string. PostgreSQL/MSSQL use `STRING_AGG`; MySQL uses `GROUP_CONCAT`; SQLite has both.
TypeScript
Exhaustive `assertNever`
Compile-time guarantee that every variant of a union is handled. When you add a new variant later, every switch missing that case becomes a type error. The runtime version is a safety net.
Kotlin
Star Projections (List<*>, etc.)
`List<*>` means "list of something I don't need to know exactly" — read-only with Any? as element type. Useful when you genuinely don't care about the parameter.
Python
chunked — Split Iterable into Fixed-Size Pieces
Lazy chunker that works on any iterable, not just lists. Common building block for batch APIs — "send 50 rows per request" — without loading the source into memory.
Kotlin
Infix Functions
A single-arg method/extension can be called without dot or parens when marked `infix`. Lets you write DSL-style code like `5 shouldBe 5` or `key to value`.
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.
HTML
Skip-to-Main-Content Link
Keyboard users (and screen-reader users) tab through every nav link before reaching content. A skip-link as the first focusable element jumps straight to <main>. Required for WCAG 2.1 AA.
Java
Stream Basics — filter / map / collect
The fluent pipeline for transforming collections. `filter` keeps matching elements, `map` transforms each one, `collect(toList())` materializes the result.
SQL
NTILE — Bucket Rows into N Buckets
Assign rows to N approximately-equal-sized buckets based on the ORDER BY. The standard way to compute quartiles, deciles, or any percentile bucket.
TypeScript
URL Builder with Type-Safe Query
Build URLs with a clean query-param API. Skips null/undefined automatically, encodes everything, and accepts arrays for repeated keys. Avoids manual string concatenation.
Bash
Unique While Preserving Order
`sort -u` re-orders. `awk '!seen[$0]++'` is the classic order-preserving dedupe — and it's a single line.
Bash
SSH to Multiple Hosts in Parallel
Run the same command on a fleet of hosts. Three patterns: serial loop (simplest), GNU parallel (fastest), pssh (purpose-built).
SQL
Cohort Retention Analysis
Group users by their signup week, then count how many were still active in each subsequent week. The classic SaaS retention table — entirely in SQL.
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.