io — Core I/O Abstractions

The io module defines the fundamental I/O contracts (Reader, Writer, Seeker, Closer) plus standard streams and helper utilities.

Core Contracts

Current exported contracts use raw byte pointers plus lengths:

contract Reader {
	read(self: &Self!, buf: &u8!, len: u64): Result<u64, IoError>;
}

contract Writer {
	write(self: &Self!, data: &u8, len: u64): Result<u64, IoError>;
	flush(self: &Self!): Result<(), IoError>;
}

contract Seeker {
	seek(self: &Self!, pos: SeekFrom): Result<u64, IoError>;
}

contract Closer {
	close(self: &Self!): Result<(), IoError>;
}

Standard I/O

let! out = stdout();
let! err = stderr();

$println("Hello, Vex!")
eprintln("Error message")

match readLine() {
	Ok(line) => $println(line),
	Err(_) => $println("read failed")
}

Helpers

• stdin() → Stream
• stdout() → Stream
• stderr() → Stream
• readLine() → Result<string, IoError>
• prompt(message: string) → Result<string, IoError>
• printInt, printFloat, printBool

Notes

• Current Reader / Writer contracts are pointer-and-length based, not Span<u8> based.
• Prefer readLine() / prompt() for simple terminal input examples.
• Use stdout().flush() when prompt text must appear before a blocking read.