[MathJax on]

### 13
External packages

The use of the packages `NormalizInterface`

[GHS14] (an interface to `Normalize`

[BIRC14]; or in its absence `4ti2Interface`

[Gut], and interface to `4ti2`

[tt]), `SingularInterface`

(an interface to `Singular`

[DGPS12]; or in its absence `Singular`

[CdG12]); or in its absence `GradedModules`

[BGJ+14] is highly recommended for many of the functions presented in this chapter. However, whenever possible a method not depending on these packages is also provided (though slower). The package tests if the user has downloaded any of the above packages, and if so puts `NumSgpsCanUsePackage`

to true, where `Package`

is any of the above.

#### 13.1
Using external packages

As mentioned above some methods are specifically implemented to take advantage of several external packages. The following functions can be used in case these packages have not been loaded prior to `numericalsgps`

.

##### 13.1-1 NumSgpsUse4ti2

`‣ NumSgpsUse4ti2` ( ) | ( function ) |

Tries to load the package `4ti2Interface`

. If the package is available, then it also loads methods implemented using functions in this package.

##### 13.1-2 NumSgpsUse4ti2gap

`‣ NumSgpsUse4ti2gap` ( ) | ( function ) |

Tries to load the package `4ti2gap`

. If the package is available, then it also loads methods implemented using functions in this package.

##### 13.1-3 NumSgpsUseNormalize

`‣ NumSgpsUseNormalize` ( ) | ( function ) |

Tries to load the package `NormalizInterface`

. If the package is available, then it also loads methods implemented using functions in this package.

##### 13.1-4 NumSgpsUseSingular

`‣ NumSgpsUseSingular` ( ) | ( function ) |

Tries to load the package `singular`

. If the package is available, then it also loads methods implemented using functions in this package.

To prevent incompatibilities, the package will not load if `SingularInterface`

has been already loaded.

##### 13.1-5 NumSgpsUseSingularInterface

`‣ NumSgpsUseSingularInterface` ( ) | ( function ) |

Tries to load the package `SingularInterface`

. If the package is available, then it also loads methods implemented using functions in this package.

To prevent incompatibilities, the package will not load if `singular`

has been already loaded.

##### 13.1-6 NumSgpsUseSingularGradedModules

`‣ NumSgpsUseSingularGradedModules` ( ) | ( function ) |

Tries to load the package `GradedModules`

. If the package is available, then it also loads methods implemented using functions in this package.

It also creates a ring of rationals `NumSgpsRationals`

.