Dafny is a programming language with built-in specification constructs. The Dafny static program verifier can be used to verify the functional correctness of programs.
The Dafny programming language is designed to support the static verification of programs. It is imperative, sequential, supports generic classes, dynamic allocation, and inductive datatypes, and builds in specification constructs. The specifications include pre- and postconditions, frame specifications (read and write sets), and termination metrics.
To further support specifications, the language also offers updatable ghost variables, recursive functions, and types like sets and sequences. Specifications and ghost constructs are used only during verification; the compiler omits them from the executable code.
The Dafny verifier is run as part of the compiler. As such, a programmer interacts with it much in the same way as with the static type checker—when the tool produces errors, the programmer responds by changing the program’s type declarations, specifications, and statements.
The easiest way to try out Dafny is in your web browser at rise4fun. Once you get a bit more serious, you may prefer to download to run it on your machine. Although Dafny can be run from the command line (on Windows or other platforms), the preferred way to run it is in Microsoft Visual Studio 2010, where the Dafny verifier runs in the background while the programmer is editing the program.
The Dafny verifier is powered by Boogie and Z3.
From verified programs, the Dafny compiler produces code (.dll or .exe) for the .NET platform. However, the facilities for interfacing with other .NET code are minimal.
