https://github.com/Microsoft/dafny

C#
Dafny is a verification-aware programming language

Dafny is a programming language with a program verifier. As you type in your program, the verifier constantly looks over your shoulders and flags any errors. Dafny is currently spread across 3 sites:

• Dafny's homepage, which contains some information about Dafny.
• This site, which includes sources, binary downloads for Windows, Mac, GNU/Linux, and FreeBSD, sources, and the issue tracker (old issues are on codeplex).
• The Rise4fun site, where you can verify Dafny programs in your web browser.

Try Dafny

The easiest way to get started with Dafny is to use rise4fun, where you can write and verify Dafny programs without having install anything. On rise4fun, you will also find the online Dafny tutorial.

Setup

See installation instructions on the wiki and instructions for installing the Dafny mode for Emacs.

Read more

Here are some ways to get started with Dafny:

• Online tutorial, focusing mostly on simple imperative programs
• 3-page tutorial notes with examples (ICSE 2013)
• Dafny Quick Reference
• Language reference for the Dafny type system, which also describes available expressions for each type
• Cheatsheet: basic Dafny syntax on two pages
• Videos at Verification Corner
• For more papers on Dafny, see the Dafny section of Rustan Leino's paper page

The language itself draws pieces of influence from:

• Euclid (from the mindset of a designing a language whose programs are to be verified),
• Eiffel (like the built-in contract features),
• CLU (like its iterators, and inpiration for the out-parameter syntax),
• Java, C#, and Scala (like the classes and traits, and syntax for functions),
• ML (like the module system, and its functions and inductive datatypes), and
• Coq and VeriFast (like the ability to include co-inductive datatypes and being able to write inductive and co-inductive proofs).

External contributions

• Haskell-to-Dafny translator, by Duncan White
• Vim-loves-Dafny mode for vim, by Michael Lowell Roberts
• Boogie-Friends Emacs mode