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Modules

Tremor-script supports nested namespaces or modules.

Modules in tremor are the lowest unit of compilation available to developers to modularise tremor logic across multiple logical namespaces. On the filesystem, modules are rooted at a base path and are nested with folders. png)

Modules can define const constants, fn functions, or nested mod sub-modules. In addition trickle modules can include define statements.

module grammar

module inner statement grammar

Module Path

Modules can be defined physically on the file system. For example given the following modular hierarchy on the file system, relative to a root module path: Nested modules can be defined as follows:

  +-- foo
+-- bar
+-- snot.tremor
+-- badger.trickle
+-- baz
+-- badger.tremor
+-- panda.trickle

The same modular hierarchy can be defined as nested module declarations as follows:

mod foo with
mod bar with
const snot = "beep";
end;
mod baz with
const badger = "boop";
end;
end;

let snot = foo::bar::snot;
let badger = foo::baz::badger;

"#{snot}-#{badger}";

or for trickle:

mod foo with
mod bar with
define tumbling window second with
interval = 1000
end;
end;
mod baz with
define tumbling window minute with
interval = 60000
end;
end;
end;

select event
from in[snot::second, badger::minute] # use our imported window definitions
into out;

Assuming this module hierarchy is rooted at /opt/my-project/lib they can be registered with tremor by prepending this folder to the TREMOR_PATH environment variable

export TREMOR_PATH="/opt/my-project/lib:$TREMOR_PATH"

Defaults

The TREMOR_PATH uses ':' on linux/unix to separate multiple module paths.

The default places to look for your modules is /usr/local/share/tremor if TREMOR_PATH is not provided.

The default place for the tremor standard library is /usr/share/tremor/lib, so the full TREMOR_PATH default is

  • /usr/local/share/tremor
  • /usr/share/tremor/lib

Referencing Modules with use

The modules can be used using the use clause as follows:

use foo::bar::snot; # snot is a ref to 'foo/bar/snot.{tremor,trickle}'
use foo::baz::badger; # badger is a ref to 'foo/bar/badger.{tremor,trickle}'

"#{snot::snot}#{badger::badger}"; # emits an interpolated string

Modules can be loaded via the use clause which in turn loads a module from the physical file system via the module path.

Inline and externalized modules can be used separately or together as appropriate.

Where there are existing references a module can be aliased to avoid clashes in the local scope:

use foo::bar as fleek;

"Hello #{fleek::snot}"

It is to be noted that inclusion via use will prevent circular inclusion as in file a.tremor can use b.tremor but beyond that point b.tremor can no longer use a.tremor as this would create a dependency cycle. This is a restriction of the current implementation and may or may not be relaxed in the future.