/**
 * The ol.proj namespace stores:
 * * a list of {@link ol.proj.Projection}
 * objects, one for each projection supported by the application
 * * a list of transform functions needed to convert coordinates in one projection
 * into another.
 *
 * The static functions are the methods used to maintain these.
 * Each transform function can handle not only simple coordinate pairs, but also
 * large arrays of coordinates such as vector geometries.
 *
 * When loaded, the library adds projection objects for EPSG:4326 (WGS84
 * geographic coordinates) and EPSG:3857 (Web or Spherical Mercator, as used
 * for example by Bing Maps or OpenStreetMap), together with the relevant
 * transform functions.
 *
 * Additional transforms may be added by using the {@link http://proj4js.org/}
 * library (version 2.2 or later). You can use the full build supplied by
 * Proj4js, or create a custom build to support those projections you need; see
 * the Proj4js website for how to do this. You also need the Proj4js definitions
 * for the required projections. These definitions can be obtained from
 * {@link https://epsg.io/}, and are a JS function, so can be loaded in a script
 * tag (as in the examples) or pasted into your application.
 * The first time there is a request for a projection, either with a
 * {@link ol.proj.projectionLike} or directly with {@link ol.proj.get}, the
 * code will check if the Proj4js library and the necessary definition are
 * loaded; if so, it will register the appropriate {@link ol.proj.Projection}
 * object and add transform functions between the new projection and all the
 * existing ones. See examples/wms-image-custom-proj for an example of this.
 * Because the check for presence of the Proj4js library and the definition only
 * takes place on the first request for them, this means they can be loaded
 * dynamically as needed; for example, with user-supplied data where you don't
 * know in advance what projections are needed, you can initially load minimal
 * support and then load whichever are requested.
 *
 * Note that Proj4js does not support projection extents. If you want to add
 * one for creating default tile grids, you can add it after the Projection
 * object has been created with `setExtent`, for example,
 * `ol.proj.get('EPSG:1234').setExtent(extent)`.
 *
 * In addition to Proj4js support, any transform functions can be added with
 * {@link ol.proj.addCoordinateTransforms}. To use this, you must first create
 * a {@link ol.proj.Projection} object for the new projection and add it with
 * {@link ol.proj.addProjection}. You can then add the forward and inverse
 * functions with {@link ol.proj.addCoordinateTransforms}. See
 * examples/wms-custom-proj for an example of this.
 *
 * Note that if no transforms are needed and you only need to define the
 * projection, just add a {@link ol.proj.Projection} with
 * {@link ol.proj.addProjection}. See examples/wms-no-proj for an example of
 * this.
 *
 * @namespace ol.proj
 */