IO

All wall IO operations return two streams - one for input and one for output - and a success code. The form of this is { 'i: <stream>, 'o: <stream> 'code: <0 -1 -2 ...> } While the code varies according to the operation, 0 always represents success. In case of failure, the length and content of the stream is undefined.

Streams

The function read takes a readable stream and a number of bytes to read as its arguments and returns a function in the form { 'bytes: <byte string>, 'read: <int> }.

The function write takes a writeable stream and a byte string as its arguments and returns the number of bytes written as an integer.

Files and Sockets

File and socket IO operations are created by specifying 'r or 'w and then the name of the file or URL of the socket.

w> a = file 'r 'foo.txt
w> a
{ 'i: <./foo.txt>, 'o: <./dev/null>, 'code: 0 }
w> b = file 'r 'does-not-exist
w> b
{ 'i: <./does-not-exist>, 'o: <./dev/null>, 'code: -1 }
w> write (socket 'w 'http://localhost:8080 'o) b"hi"
2
w> write (file 'w 'hello.txt 'o) b"world"
5
w> read (file 'r 'hello.txt 'i) 5
b"world"

In addition to files persisted to disk, file supports standard posix pipes like /dev/stdin. In the case of reads from pipes and sockets, the reading operation is blocking until a write has occured.