Modules

As we saw with "maths", modules of code can be imported to provide data and functions in addition to the built-in ones.

For example, the os module has a relation generator named cwd which returns the 'current working directory'.

import("os")
os.cwd

┌──────────┐
│ dirname  │
├──────────┤
│ localdir │
└──────────┘

There's also a relation generator os.file which, given one or more dirname, returns the filenames in those directories. So we can compose the two of them to get a list of the files in the current directory.

os.file(os.cwd)

┌─────────────────┬─────────────────────────┬───────┬──────┬────────┬─────┐
│ filename        │ path                    │ ext   │ size │ is_dir │ err │
├─────────────────┼─────────────────────────┼───────┼──────┼────────┼─────┤
│ test.txt        │ /localdir/test.txt      │ .txt  │   49 │ false  │     │
│ subdir          │ /localdir/subdir        │       │ 4096 │ true   │     │
└─────────────────┴─────────────────────────┴───────┴──────┴────────┴─────┘

Futhermore, there's another relation generator os.file_content which, given one or more file path, returns the contents of those files. So we can compose all three, and we can use all our relational query features to get a list of selected files and their contents.

os.file_content(os.file(os.cwd)[not is_dir])

┌──────────┬──────┬──────┬────────┬─────┬────────┬────────────────────────────────────────────┐
│ filename │ ext  │ size │ is_dir │ sep │ format │ r                                          │
├──────────┼──────┼──────┼────────┼─────┼────────┼────────────────────────────────────────────┤
│ test.txt │ .txt │   49 │ false  │     │        │ ┌─────┬──────────────────────────────────┐ │
│          │      │      │        │     │        │ │ seq │ ss                               │ │
│          │      │      │        │     │        │ ├─────┼──────────────────────────────────┤ │
│          │      │      │        │     │        │ │   0 │ This is a test file              │ │
│          │      │      │        │     │        │ │   1 │                                  │ │
│          │      │      │        │     │        │ │   2 │ It has several lines             │ │
│          │      │      │        │     │        │ │   3 │ of text.                         │ │
│          │      │      │        │     │        │ └─────┴──────────────────────────────────┘ │
└──────────┴──────┴──────┴────────┴─────┴────────┴────────────────────────────────────────────┘

The file contents are currently read into lines but in future we'll be able override that by passing a variety of format and sep options. For now we can re-combine the lines if we want to form a single block of file data, e.g. using str_rel.

os.file_content(os.file(os.cwd)[not is_dir])(str_rel){filename, s}

┌─────────────────────────┬──────────┐
│ s                       │ filename │
├─────────────────────────┼──────────┤
│ This is a test file     │ test.txt │
│                         │          │
│ It has several lines    │          │
│ of text.                │          │
└─────────────────────────┴──────────┘

Or we can read in a whole binary file by using format:="b".