Andrew Walpole TCotton

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Focusing

London-based software engineer

TCotton / branded.ts

Last active November 29, 2025 12:20

branded types

	/**
	Branding in TypeScript is a technique for creating opaque, nominal, or distinct types even when they
	have the same underlying structure.

	It’s one of the most useful advanced type tricks in TS, because the language is otherwise structurally typed. **/

	// Branding:

	// Makes structurally identical types distinct

TCotton / effect-drizzle-error-handling.ts

Created November 26, 2025 15:42

Effect PostgreSQL and Drizzle with error handling

	import { DbSchema } from '@repo/database/schema'
	import { type ExtractTablesWithRelations } from 'drizzle-orm'
	import { drizzle, type NodePgDatabase, type NodePgQueryResultHKT } from 'drizzle-orm/node-postgres'
	import { type PgTransaction } from 'drizzle-orm/pg-core'
	import { Cause, Context, Data, Effect, Exit, Layer, Option, Redacted, Runtime } from 'effect'
	import * as pg from 'pg'

	type TransactionClient = PgTransaction<
	NodePgQueryResultHKT,
	typeof DbSchema,

TCotton / useful.ts

Last active November 29, 2025 10:40

TypeScript cheatsheet

	// return types from functions
	type P = ReturnType<typeof dateFromUUIDv7>;

	// return type with promise
	type P = Awaited<ReturnType<typeof dateFromUUIDv7>>;

	// see all types
	type PrettifyPromise<T> = {
	[K in keyof T]: T[K] extends Promise<infer U> ? U : T[K];
	} & {}

TCotton / briggs.hs

Created October 26, 2025 17:04

Use of every and superimpose

	d3
	$ every 4 ( superimpose
	( slice 2 (fast "2" "[1 2 3 4]" ) -- re-slice give variation of slight glitch
	. (\|+\| gain "0.1") -- slightly louder
	. ( # sound "bd*4") -- different sound from the bDrums
	))
	$ every 2 ( superimpose
	( (\|+\| gain "-0.2") -- slightly quieter
	. (0.25 <~) -- delay by 1/4 cycle
	. (slice 4 (fast "2" "[1 3 2 4]")) -- re-slice + rearrange

TCotton / fadetozero.hs

Created September 20, 2025 15:53

	let spread1 = (spread ($) [jux rev, rev])
	spread2 = spread ($) [density 2, rev, slow 2, striate 3, (# speed "0.8")]
	juxrev = jux rev
	revEffect = rev
	palindrom = palindrome
	fadeOut = range 1 0 $ slow 16 saw
	in d4 $ stack [(
	slow 2
	$ chop 32
	$ sound "piano_c"

TCotton / demo.hs

Last active September 19, 2025 17:19

Example of TidalCycle and as used on the YouTube demonstraton

	cps (120/60/4)

	-- drum patterns in do block

	do
	let drumz1 = every 4 (\|> sound "drum")
	$ sound "[drum <dr:2>] drum *2"
	# gain 0.7
	# orbit 0 -- routed to audiochannel 1-2
	let drumz2 = sound "[drum <dr:1>] drum [drum <techno:5>] drum /2"

TCotton / tidalCycle-example

Created September 10, 2025 14:56

TidalCycle example

	setcps (120/60/4)

	-- drum patterns in do block

	do
	let drumz1 = every 4 (\|> sound "drum")
	$ sound "[drum <dr:2>] drum *2"
	# gain 0.6
	# orbit 0
	let drumz2 = sound "[drum <dr:1>] drum [drum <techno:5>] drum /2"

TCotton / typescript-autocomplete.ts

Created August 19, 2025 07:26

typescript autocomplete

TCotton / not-enum.ts

Created August 19, 2025 05:55

Better TypeScript ENUMs

	const LOG_LEVEL = {
	DEBUG: "DEBUG",
	WARNING: "WARNING",
	ERROR: "ERROR",
	} as const
	type ObjectValues <T> = T[keyof T];
	type LogLevel = ObjectValues<typeof LOG_LEVEL>

TCotton / hook.js

Created May 17, 2021 10:55

Stale data invalidation

	const swr = new Map;

	const useSWR = (path, fetcher, cache) => {
	let [data, update] = useState(null);
	if (!swr.has(path) \|\| swr.get(path) !== cache) {
	fetcher(path).then(update, () => update(new Error(path)));
	swr.set(path, cache);
	}
	const isError = data instanceof Error;
	return {