Imandra comes with several different directives for loading files or including external modules.

It can be a bit daunting initially to undertstand which directive to use in the appropriate context, let's look at each in detail:

## use¶

Syntax: #use "filename.iml";; or [@@@use "filename.iml"]

The behavior of use is that of reading the content of "filename.iml" and evaluating it into the current environment, as if each definition had been directly entered into the toplevel.

The use directive is meant to used in interactive sessions rather than in library/production code, and is not recursive.

There exist a functional equivalent of the directive, called System.use that can be used to (recursively) load files at runtime, this is often useful to implement the common pattern of having a top.iml file responsible for loading the entire model one is working on, or more generally for programmatic loading of imandra files.

If filename.iml is a relative path, it is resolved to an absolute path by searching for it in Imandra's load path.

The current directory is always implicitly part of the load path, and additional directories can be added dynamically via the directory directive, or at startup using the -dir argument.

## mod_use¶

Syntax: #mod_use "filename.iml";; or [@@@mod_use "filename.iml"]

mod_use behaves exactly like use, with the only exception that the contents of the file will be evaluated in the toplevel as if they were wrapped in a module called Filename

The functional equivalent of the directive is System.mod_use

## use_gist¶

Syntax: #use_gist "my-user/gist-hash";; or [@@@use_gist "my-user/gist-hash"]

use_gist behaves exactly like use, except instead of loading a local path it will download the gist content and load that in the current environment.

## import¶

Syntax: #import "filename.iml";; or [@@@import "filename.iml"]

The behavior of import is similar to that of mod_use, with a number of significant differences:

• toplevel directives are disabled in the file being imported
• import is idempotent, as it caches on first import
• Imandra resolves the import at compile time, so the imported module is available when typechecking the remainder of the file

As such, import can be considered a version of mod_use to be used in IML libraries as opposed to during interactive development.

Like use and mod_use, import uses Imandra's load path to search for files, when importing an IML library, the current directory will be temporary set to that of the library itself.

## require¶

Syntax: #require "some-lib";; or [@@@require "some-lib"] or as an argument to imandra: -require somelib

The behavior of require is to search for some-lib in the list of installed libraries (using topfind) and load it in the current environment.

If some-lib comes packaged with a some-lib.iml file, it will be automatically loaded by Imandra using #import after the library has been required.

## require_use¶

Syntax: #require_use "some-lib";; or [@@@require_use "some-lib"] or as an argument to imandra: -require-use somelib

Similar to #require "some-lib";; except it loads the file some-lib.iml with #use instead of #import, so no module is created, and it's not idempotent.

## require_mod_use¶

Syntax: #require_mod_use "some-lib";; or [@@@require_mod_use "some-lib"] or as an argument to imandra: -require-mod-use somelib

Similar to #require "some-lib";; except it loads the file some-lib.iml with #mod_use instead of #import, so it's not idempotent.