🧿 Pipefish

Welcome to Pipefish!

Welcome to Pipefish, a new programming language. This is version 0.5.9; you shouldn't use it in production but it's good enough at this point for you to install it and play around with it. (Note: at time of writing, September, I have just changed the main branch from the prototype treewalker to the compiler/vm implementation. It is therefore probably rather flaky and needs me to test it hard for a couple of weeks.)

There are batteries included; there is tooling; there is a wiki; there are plenty of features including some you've never heard or thought of.

Pipefish aims to be a delightful general-purpose language particularly suitable for rapid development of CRUD apps. With the semantics of a functional language, with syntax borrowed from mainstream productivity languages (specifically Python and Go), and with inspiration mainly from SQL and Excel — Pipefish is not quite like anything you've ever seen. But it is also a very practical language that exists to solve some very ordinary "white-collar" problems.

It is my hope either that Pipefish itself will one day be used in production, or (given my amateur status and lack of time) that this project will get enough attention that my ideas will be copied by people with more money and personnel and expertise. To this end, please add a star to the repo! Thank you!

Instructions for installing Pipefish can be found here, as part of a general manual/tutorial wiki that tells you everything you need to know to code in Pipefish. There are lots of other supporting documents.

A little Pipefish

Here is some sample code: you should find it readable.

cmd    // An imperative command.

greet :
    get name from Input("What's your name? ")
    post "Hello " + name + "!"

def    // A pure function.

factorial(n) :
    n == 0 :
        1
    n > 0 :
        n * factorial n - 1
    else :
        error "can't take the factorial of a negative number"

Distinguishing features

Here are some of Pipefish's more distinctive features:

Pipefish services have a functional core, imperative shell architecture, in which a thin layer of IO sits on top of pure functional business logic.
All values are immutable; all comparison is by value.
Functions are pure and referentially transparent.
Local constants of functions are defined in a block at the end of the function and evaluated only if/when required. (You don't know how nice this is until you've tried it.)
Free order of intitialization also helps you to write your scripts top-down.
Abstraction is achieved by overloading and duck-typing. There is multiple dispatch.
Field names of structs are first-class objects. Indexing structs and maps overloads the same operator.
While Pipefish is very dynamic (as illustrated in the previous two points) it is also very strongly typed, much more so than any mainstream dynamic language.
Pipefish is REPL-oriented, with livecoding to make it easy to code and test incrementally.
The REPL is also a development environment and framework. It lets you test your code, write permanent tests, ask for help, interact with error messages, configure your services, deploy them to the web and manage access to them.
It is intended that often a Pipefish service will act as its own front end (like e.g. a SQL database does) with the end-user talking to it via the Pipefish REPL. For this reason Pipefish has an unusually flexible syntax for creating DSLs.
Pipefish comes with Go and SQL interop for all your backend needs.
(Also the system for embedding other languages is extensible if this does not in fact meet all your needs.)
Pipefish allows and encourages you to write your applications as microservices, giving you a natural way to encapsulate data and manage access to it.
Pipefish’s syntax is based on mainstream productivity languages, principally Python and Go. It has a shallow or indeed invisible learning curve: you can learn the simple parts of the language without knowing that the other parts exist.
Pipefish's roadmap includes a point where we freeze the core language around a small set of sufficiently powerful features and try to remain permanently in version 1.x.

Documents

The Pipefish manual/wiki. A complete guide to coding in Pipefish.
Pipefish: a high-level view. This explains the goals and design principles of the language.
Style guide. This gives best practices for the style in which one should write Pipefish code.
Functional core, imperative shell. A synopsis of the language paradigm.
The whys of Pipefish. This explains the reasoning behind some lower-level design choices which are sufficiently unusual as to need explanation.

Licensing