key x     key[x]

Key of a dictionary

Where x is a dictionary (or the name of one), returns its key.

A namespace is a dictionary.

Keys of a keyed table

Where x is a keyed table (or the name of one), returns its key column/s.

Files in a folder

Where x is a directory handle returns a list of objects in the directory, sorted ascending.

Whether a folder exists

An empty folder returns an empty symbol vector; a non-existent folder returns an empty general list.

Whether a file exists

Where x is a file handle, returns the descriptor if the file exists, otherwise an empty list.

Note that

• an empty directory returns an empty symbol vector
• a non-existent directory returns an empty general list

Whether a name is defined

Where x is a symbol atom that is not a file or directory descriptor, nor the name of a dictionary or table, returns the original symbol if a variable of that name exists, otherwise an empty list. The name is interpreted relative to the current context if not fully qualified.

Target of a foreign key

Where x is a foreign-key column returns the name of the foreign-key table.

Type of a vector

Where x is a vector returns the name of its type as a symbol.

Enumerator of a list

Where x is an enumerated list returns the name of the enumerating list.

til

Where x is a non-negative integer returns the same result as til.