File_Import.rst

File Import

file filename

Evaluate the program stored in the file named filename, and return the resulting value. filename is a string.

The Curv file operation can import data from multiple file formats, of which the text-based Curv language (*.curv files) is just one example. All of these file formats are considered "source files", and all of them are "evaluated" to produce a value.

Supported file formats:

Filename Extension	Description
*.curv	Curv language source file
none, directory	Directory syntax

More graphical file formats will be added to this list in the future.

The file operator works as follows:

• If filename names a directory, then the file is imported using directory syntax.
• Otherwise, if the filename extension is one of the extensions in the above table, then the file is imported based on its extension.
• Otherwise, by default, the file is interpreted as a Curv language source file.

Directory Syntax

In the directory syntax, the filename names a directory (also known as a folder), instead of a regular file.

A directory is evaluated to produce a record value, with one record field for each contained file of a recognized type. (Files of an unknown type are ignored.) For each file contained within the directory,

• If the filename begins with ., then it is ignored.
• Otherwise, if the file is a directory, and the filename has no extension, then it is imported using directory syntax. The corresponding record field name is the filename.
• Otherwise, if the file is a regular file and the filename extension is one of the known extensions in the above table, then the file is imported based on its extension. The corresponding record field name is the filename with its extension removed.

The record values constructed by parsing directory syntax use lazy evaluation. The file contents of a record field are not read into memory and converted to a value until the field value is required. This means you can import a large directory, or a deep directory hierarchy, containing many *.curv files, without reading and evaluating all of those files.