# Extracting OCaml modules with imandra-extract¶

When developing code with Imandra, we write our programs in .iml (Imandra-ml), or .ire (Imandra-reason) for Reason syntax.

Imandra is both a programming language and a logic, and as such it incorporates arbitrary precision (integer and rational) arithmetic with their standard mathematical semantics. This deviates from 'normal' OCaml in which int is of fixed precision, for example.

When using Imandra, this arbitrary precision semantics is used both for code execution and reasoning. For example, during an Imandra session, integer literals are parsed as values of the arbitrary precision Z.t type, resp., rather than to standard (OCaml) machine integers.

Imandra also comes with its own prelude of functions that have been pre-verified, imandra-prelude.

As well as reasoning about them, you can execute your .iml and .ire programs directly with Imandra itself. However at some point you will probably want to compile a verified module or group of modules into a larger program using an OCaml toolchain (either the standard OCaml toolchain or Bucklescript). This is where imandra-extract fits in, allowing you to extract .ml and .re files.

The imandra-extract binary comes bundled with your Imandra installation.

## Example¶

let int_of_bit (a : bool) : Z.t =
if a then 1 else 0

let rec int_of_bits (a : bool list) : Z.t =
match a with
| [] -> 0
| a :: a' -> int_of_bit a + 2 * (int_of_bits a')


We can then use imandra-extract on this file:

imandra-extract my_module.iml -o my_module.ml


This creates an .ml file similar to the following:

(* generated by imandra-extract from "my_module.iml" *)

open Imandra_prelude;;

(* start generated code here *)

#1 "test.iml"
let int_of_bit (a : bool) =
(if a then Z.of_string "1" else Z.of_string "0" : Z.t)

#4 "test.iml"
let rec int_of_bits (a : bool list) =
(match a with
| [] -> Z.of_string "0"
| a::a' ->
(int_of_bit a) + ((Z.of_string "2") * (int_of_bits a')) :
Z.t)


As you can see, the literals are wrapped with the appropriate Z conversion functions, and the Imandra_prelude module has been opened (which is opened implicitly when running Imandra).

As this is now just a regular .ml program, it can be compiled alongside other OCaml modules - you will however need to install the extracted imandra-prelude as a dependency in your project. View the project and README for imandra-prelude on GitHub: https://github.com/aestheticIntegration/imandra-prelude.