Loads the given module.
The function starts by looking into the package.loaded table
to determine whether modname is already loaded.
If it is, then require returns the value stored
at package.loaded[modname] .
Otherwise, it tries to find a loader for the module.
To find a loader,
require is guided by the package.loaders array.
By changing this array,
we can change how require looks for a module.
The following explanation is based on the default configuration
for package.loaders .
First require queries package.preload[modname] .
If it has a value,
this value (which should be a function) is the loader.
Otherwise require searches for a Lua loader using the
path stored in package.path .
If that also fails, it searches for a C loader using the
path stored in package.cpath .
If that also fails,
it tries an all-in-one loader (see package.loaders ).
Once a loader is found,
require calls the loader with a single argument, modname .
If the loader returns any value,
require assigns the returned value to package.loaded[modname] .
If the loader returns no value and
has not assigned any value to package.loaded[modname] ,
then require assigns true to this entry.
In any case, require returns the
final value of package.loaded[modname] .
If there is any error loading or running the module,
or if it cannot find any loader for the module,
then require signals an error. |