use

The use keyword imports an IRL package or artifact.

Purpose

This keyword is used to import an IRL package or artifact.

Context

Packages

Syntax

use [packageName.] artifactName | packageName.*;

Description

The effect of referencing artifacts is different depending on whether they belong to the default package or not.

Using an artifact from another package

To use an artifact from another package, write this statement if the artifact is a variable, rule, or task: 

use artifactName;

For functions, the syntax is more complex because you must uniquely identify the artifact that you want to import. To do so, include the function signature in the use statement: 

use displayPrice(double);
Referencing artifacts in the default package

To reference artifacts from the default package in package B, you can import the artifacts one by one (not necessarily all of them) from the default package, using the use keyword. Only these artifacts are visible in package B.

When artifact names conflict, the following rule applies: If the default package defines an artifact named artifactName and package B defines an artifact also named artifactName and uses package A, all references to artifactName in B are considered to be references to the B artifact and priority is given to the local artifact. There is no way to reference the artifact in the default package.

Referencing another package that is not the default

To reference artifacts from package A (A not being the default package) in package B, you can do one of the following:

  • You can write a use statement to import package A into package B. In this case, all its artifacts are visible in package B.

  • If you can import artifacts from package A one by one (not necessarily all of them) uisng the use keyword. In this case, only the imported artifacts are visible in package B.

When artifact names conflict, the following rules apply:

  • If package A defines an artifact named artifactName and package B defines an artifact also named artifactName and uses package A, all references to artifactName in package B are considered to be references to the B artifact and priority is given to the local artifact. To reference the A artifact, you must use its fully qualified name.

  • If two packages A and B define an artifact named artifactName, and if package C® uses packages A and B and references the artifactName artifact, an error is raised because it is impossible to give priority to a package against another. To avoid any ambiguity, use the fully qualified name.

Example

This example defines two packages, pricing and europe.pricing. The displayPrice function belongs to the default package. The europe.pricing package uses the pricing package and the displayPrice function. 

function void displayPrice(double price)
{
  ...
}
package pricing
{
  variables {
     Customer customer;
  }
  rule isEligible
  {
    when {
    ...
    }
    then {
    ...
    }
  }
}

package europe.pricing
{
  use pricing.*;   All the pricing package is imported. All its artifacts are 
visible in this package
  use displayPrice(double); The function displayPrice from the default package 
is imported
  ruletask main
  {    
    body {
     isEligible
    } 
    finalaction {
      displayPrice(3.2d);
    }
  }
}