The GNAT Library (GNAT Reference Manual)

## 13 The GNAT Library ¶

The GNAT library contains a number of general and special purpose packages. It represents functionality that the GNAT developers have found useful, and which is made available to GNAT users. The packages described here are fully supported, and upwards compatibility will be maintained in future releases, so you can use these facilities with the confidence that the same functionality will be available in future releases.

The chapter here simply gives a brief summary of the facilities available. The full documentation is found in the spec file for the package. The full sources of these library packages, including both spec and body, are provided with all GNAT releases. For example, to find out the full specifications of the SPITBOL pattern matching capability, including a full tutorial and extensive examples, look in the `g-spipat.ads` file in the library.

For each entry here, the package name (as it would appear in a `with` clause) is given, followed by the name of the corresponding spec file in parentheses. The packages are children in four hierarchies, `Ada`, `Interfaces`, `System`, and `GNAT`, the latter being a GNAT-specific hierarchy.

Note that an application program should only use packages in one of these four hierarchies if the package is defined in the Ada Reference Manual, or is listed in this section of the GNAT Programmers Reference Manual. All other units should be considered internal implementation units and should not be directly `with`ed by application code. The use of a `with` clause that references one of these internal implementation units makes an application potentially dependent on changes in versions of GNAT, and will generate a warning message.