Awesome

NOTE: Tidy is still under development and this repository is not yet ready for public consumption. Most development is going on in the underlying typy repository for now.

Tidy

Typed functional programming is on the rise, but for many Python programmers it just isn't practical to switch outright to a typed functional language like OCaml or Haskell. Consider the following totally-not-made-up quotes:

"I'm not about to spend months rewriting all of these great Python statistics routines!"

"The rest of my research group uses Python, and we need to be able to interface with each other's code cleanly."

Tidy aims to address these concerns by embedding a typed functional programming language cleanly into Python, as a library. You can install Tidy by running pip install tidy today.

Hello, World!

Here is the heart of a tidy functional "Hello, World!":

def hello(x : string): 
    "Hello, " + x + "!"
print(hello("World"))

Notice that the function hello does not need to explicitly return -- like other functional languages, Tidy is expression-oriented. The return type, string, is inferred. Tidy allows side effects, like printing, anywhere (i.e. it can be considered an impure functional language in the ML tradition.)

Tidy code must appear inside a Tidy module:

import tidy

@tidy.module
def Hello():
    def hello(x : string): 
        "Hello, " + x + "!"
    print(hello("World"))

The module body is parsed by Python, then typechecked and translated to Python by tidy before it is evaluated. This needs to happen only once, even if hello is called many times.

Language Features

Simple functions like hello are, of course, just the beginning. Tidy features all the typed functional essentials...

• algebraic datatypes (tuples, labeled tuples and labeled sums)
• pattern matching
• parametric polymorphism
• local type inference

...plus, fast and clean two-way interoperability with Python.

If you're already familiar with a typed functional language, you might be interested in a side-by-side comparison with OCaml (TODO). The manual (TODO) gives the full details. If you're not familiar with a typed functional language, start with "what is typed functional programming, and why should I care?" (TODO)

License

tidy is released under the permissive MIT License, requiring only attribution in derivative works.