Before the system had the ability to open resources as files,
resources were opened using the predicates open_resource/2
or open_resource/3.
These predicates provide somewhat better dynamic control over resources
depending on whether the code is running from files or from a saved
state. The main disadvantage is that having a separate open call
requires rewriting code to make it work with resources rather than
files.
- open_resource(+Name,
-Stream)
- open_resource(+Name,
-Stream, +Options)
- Opens the resource specified by Name. If successful, Stream
is unified with an input stream that provides access to the resource.
The stream can be tuned using the Options, which is a subset
of the options provided by open/4.
- type(Type)
- encoding(Encoding)
- bom(Bool)
- Options that determine the binary/text type, encoding for text streams
and whether or not the content should be checked for a BOM marker. The
options have the same meaning as the corresponding options for open/4.
The predicate open_resource/3
first checks resource/2.
When successful it will open the returned resource source file.
Otherwise it will look in the program's resource database. When creating
a saved state, the system normally saves the resource contents into the
resource archive, but does not save the resource clauses.
This way, the development environment uses the files (and
modifications) to the resource/3
declarations and/or files containing resource info, thus immediately
affecting the running environment, while the runtime system quickly
accesses the system resources.
