Documentation

Getting Started

• Installing Duso
• Learning Duso

Guides

• Performance Report vs. Node, Python, Ruby
• How to Bundle Applications
• Files and Modules
• Debugging Scripts
• Virtual Filesystem

Libraries

Standard Library (stdlib)

• ansi ANSI color and terminal styling utilities
• docserver Embedded documentation server with caching

Community Libraries (contrib)

• azure-ai Azure OpenAI API for accessing GPT-4, Claude, and other hosted models
• claude Anthropic Claude API integration with multi-turn conversations and tools
• couchdb CouchDB database client with CRUD operations and Mango queries
• deepseek DeepSeek LLM API idiomatic interface
• gemini Google Gemini API with OpenAI-compatible interface
• grok xAI Grok LLM API with OpenAI-compatible interface
• groq Groq ultra-fast inference API
• ollama Local LLMs through Ollama’s OpenAI-compatible API
• openai OpenAI API with options-based interface
• phospher Phospher Icons SVG inline icon fetcher
• stripe Stripe payment processing API
• svgraph SVG chart and graph generation
• zlm “Zero Language Model” for testing LLM-scale scenarios without burning tokens

Language Keywords

Variables

• var Variable declaration
• raw Raw string/template modifier

Syntax

• comments Using comments in code

Logic

• if then elseif else end Conditional statements
• end Block terminator keyword
• and or not Logical AND, OR, and NOT

Loops

• for in Loop with iteration
• while do Loop while condition is true
• break Exit loop early
• continue Skip to next iteration

Functions

• function Define a function
• return Return from function

Exceptions

• try Try-catch error handling
• catch() Catch errors from try block
• throw(msg) Throw an error with call stack information

Types

• array Ordered list of values
• binary Immutable binary data (files, images, etc.)
• boolean True or false
• code Pre-parsed source code value
• error Error value with message and stack trace
• nil Null/undefined value
• number Floating-point number
• object Key-value data structure
• string Text value

Built-in Functions

Strings

• contains(str, pattern) Check if contains pattern (supports regex)
• find(str, pattern) Find all matches, returns array of {text, pos, len} objects (supports regex)
• join(array, sep) Join array elements into single string
• len(value) Get the length of arrays, objects, or strings
• lower(str) Convert to lowercase
• pad_left(str, width, char) Pad on the left to reach desired width
• pad_right(str, width, char) Pad on the right to reach desired width
• repeat(str, count) Repeat string multiple times
• starts_with(str, prefix) Check if string starts with prefix
• ends_with(str, suffix) Check if string ends with suffix
• replace(str, pattern, replacement) Replace all matches of pattern with replacement string or function result (supports regex)
• split(str, sep) Split string into array by separator
• substr(str, pos, length) Get text, supports negative length
• template(str) Create reusable template function from string with {{expression}} syntax
• trim(str) Remove leading and trailing whitespace
• upper(str) Convert to uppercase

Arrays & Objects

• deep_copy(value) Deep copy of arrays/objects; functions removed (safety for scope boundaries)
• filter(array, fn) Keep only elements matching predicate
• keys(obj) Get array of all object keys
• map(array, fn) Transform each element with function
• pop(array) Remove and return last element
• push(array, values...) Add elements to end, returns new length
• range(start, end, step) Create array of numbers in sequence
• reduce(array, fn, init) Combine array into single value
• shift(array) Remove and return first element
• sort(array, fn) Sort array in ascending order
• unshift(array, values...) Add elements to beginning, returns new length
• values(obj) Get array of all object values

Math

• abs(n) Absolute value
• ceil(n) Round up to nearest integer
• clamp(val, min, max) Constrain value between min and max
• floor(n) Round down to nearest integer
• max(nums...) Find maximum value
• min(nums...) Find minimum value
• pow(base, exp) Raise to power (exponentiation)
• random() Get random float between 0 and 1 (seeded per invocation)
• round(n) Round to nearest integer
• sqrt(n) Square root
• acos(x) Inverse cosine (arccosine), x between -1 and 1, returns radians
• asin(x) Inverse sine (arcsine), x between -1 and 1, returns radians
• atan(x) Inverse tangent (arctangent), returns radians
• atan2(y, x) Inverse tangent with quadrant correction, returns radians
• sin(angle) Sine of angle in radians
• cos(angle) Cosine of angle in radians
• tan(angle) Tangent of angle in radians
• exp(x) E raised to the power x
• log(x) Logarithm base 10
• ln(x) Natural logarithm (base e)
• pi() Mathematical constant π (3.14159…)

File I/O

• load(path) Read file contents as string
• load_binary(path) Read file as immutable binary data
• save(path, content) Write string to file (create/overwrite)
• save_binary(binary, path) Write binary data to file
• append_file(path, content) Append content to file (create if needed)
• copy_file(src, dst) Copy file (supports /EMBED/ for embedded files)
• move_file(src, dst) Move file from source to destination
• rename_file(old, new) Rename or move a file
• remove_file(path) Delete a file
• list_dir(path) List directory contents with {name, is_dir}
• list_files(path) List files in directory recursively
• make_dir(path) Create directory (including parent directories)
• remove_dir(path) Remove empty directory
• file_exists(path) Check if file or directory exists
• file_type(path) Get file type (“file” or “directory”)
• current_dir() Get current working directory
• watch(path, timeout) Monitor file or directory for changes

Image Processing

• load_image(path) Load image from file
• save_image(image, path) Save image to file
• scale_image(image, max_x, max_y, mode) Scale image with fit/fill/stretch modes
• crop_image(image, x, y, width, height) Extract rectangular region from image
• rotate_image(image, degrees) Rotate by 90, 180, or 270 degrees
• flip_image_x(image) Flip horizontally (left-right mirror)
• flip_image_y(image) Flip vertically (top-bottom mirror)
• grayscale_image(image) Convert to grayscale
• convert_image(image, format) Convert between PNG, JPEG, and GIF formats
• composite_image(base, overlay, x, y, blend) Layer overlay on base with blend modes
• set_image_opacity(image, opacity) Set absolute opacity (0.0-1.0)
• adjust_image_opacity(image, factor) Multiply opacity by factor

Network & HTTP

• fetch(url, options) Make HTTP requests (JavaScript-style fetch API)
• http_server(config) Create HTTP server for handling requests

I/O

• input(prompt) Read line from stdin, optionally display prompt
• print(values...) Output values to stdout, separated by spaces
• write(values...) Output values to stdout without newline at the end
• busy(message) Display a loading/busy message to stderr

Date & Time

• format_time(timestamp, format) Format timestamp to string
• now() Get current Unix timestamp in local timezone
• timestamp(timezone) Get current Unix timestamp in UTC or a specific timezone/offset
• timer() Get current time with sub-second precision for benchmarking
• parse_time(str, format) Parse time string to timestamp
• sleep(duration) Pause execution for duration in seconds (default: 1)

Encoding

• encode_base64(str|binary) Encode string or binary to base64
• decode_base64(str) Decode base64 string to binary
• format_csv(array, delimiter) Format array of arrays to CSV string
• parse_csv(str, delimiter) Parse CSV string to array of arrays
• format_json(value, indent) Convert value to JSON string (stringifies binary, functions, errors)
• parse_json(str) Parse JSON string
• markdown_html(text, options) Render markdown to HTML
• markdown_ansi(text, theme) Render markdown to ANSI terminal output with colors
• markdown_text(text) Render markdown to plain text

Modules

• include(path) Execute script in current scope
• require(path) Load module in isolated scope, return exports

Types

• tobool(value) Convert to boolean
• tonumber(value) Convert to number
• tostring(value) Convert to string
• type(value) Get type name of variable

Flow & Concurrency

• context() Get runtime context for a scripts or nil if unavailable
• exit(value) Exit script with optional return value
• parallel(fns) Execute functions concurrently
• parse(source, metadata) Parse code string into code or error value (never throws)
• run(script, context) Execute script synchronously and return result
• spawn(script, context) Run script in background goroutine and return numeric process ID
• kill(pid) Terminate a spawned process by PID

Debugging

• breakpoint(args...) Pause execution and enter debug mode (enable with -debug)
• watch(exprs...) Monitor expression values and break on changes (enable with -debug)
• throw(msg) Throw an error with call stack information

Testing

• assert(condition, message) Check a condition and throw an error if false

System & Data Storage

• sql(namespace, config) Create or retrieve a MySQL-compatible database connection pool
• datastore(namespace, config) Access a named thread-safe in-memory key/value store with optional persistence
• sys(key) Access system information and CLI configuration values
• doc(topic) Access documentation for modules and builtins
• env(name) Read environment variable
• uuid() Generate RFC 9562 UUID v7 (time-ordered, sortable unique identifier)

Security

• hash(algo, data) Compute cryptographic hash of string or binary (sha256, sha512, sha1, md5)
• hash_password(password, cost) Hash password with bcrypt for secure storage
• verify_password(password, hash) Verify password against bcrypt hash
• sign_rsa(data, private_key_pem) Sign data with RSA private key (SHA256-PKCS1v15)
• verify_rsa(data, signature, public_key_pem) Verify RSA signature
• rsa_from_jwk(n, e) Convert JWK modulus and exponent to PEM-encoded RSA public key
• sign_ec(data, private_key_pem) Sign data with EC private key (ES256, P-256 curve)
• verify_ec(data, signature, public_key_pem) Verify EC signature (ES256, P-256 curve)
• ec_from_jwk(x, y) Convert JWK x,y coordinates to PEM-encoded EC public key (P-256)