Quick Start

Delta is a browser-based workbench for building and simulating formal automata. You write machines as TypeScript, compile them in the editor, and interact with them through a visual debugger and test suite — no local setup required.

Importing from delta:lib

All builders and utilities are available from a single virtual module:

import { nfa, dfa, tm, multitape, thompson, EPS, q, convertToDFA } from 'delta:lib'

This is the only import you need. delta:lib is resolved automatically by the workbench — you don't install anything.

Writing a Machine

Every machine is built with a fluent builder, then returned as the file's default export. The workbench reads the default export and uses it for simulation and visualization.

import { dfa } from 'delta:lib'
 
export default dfa('even number of 1s')
  .alphabet('0', '1')
  .states('q0', 'q1')
  .start('q0')
  .accept('q0')
  .transition('q0', '0', 'q0')
  .transition('q0', '1', 'q1')
  .transition('q1', '0', 'q1')
  .transition('q1', '1', 'q0')
  .build()

A missing export default, or a build error thrown by .build(), will be surfaced as a compile error.

The Editor

The Code tab contains a Monaco editor with full TypeScript support. Autocomplete and type checking work against the delta:lib types as you type.

Cmd+S (or the compile button) compiles your code and updates the visualization. The status indicator in the header shows:

• ✓ valid — machine compiled and is ready
• ✗ check errors — one or more errors; red underlines in the editor show exactly where, with hover tooltips giving details

Recipes

The dropdown in the header lists pre-built example machines. Selecting one loads its code into the editor and populates the test suite with relevant inputs. It's a good way to explore language patterns or start from a working baseline.

Sharing

The share button (icon next to the machine name) copies a URL that encodes the current machine code. Anyone who opens the link lands directly in the workbench with your machine loaded.

Graph

On desktop, the right panel always shows a Graphviz diagram of the compiled machine. You can export it as PNG, SVG, or raw DOT source using the actions in the graph header.

Tests

The Tests panel (right sidebar on desktop; Tests tab on mobile) lets you define a set of input strings and check whether the machine accepts or rejects each one.

You can also import and export test cases as JSON.

Helper: q(lower, upper)

Generates sequential state names ["q0", "q1", ..., "qN"]:

import { q } from 'delta:lib'
 
builder.states(...q(0, 7)) // → "q0" through "q7"