diff --git a/src/ona/io.zig b/src/ona/io.zig
index 7714365..c939f49 100644
--- a/src/ona/io.zig
+++ b/src/ona/io.zig
@@ -98,6 +98,12 @@ pub const FileAccess = struct {
     }
 };
 
+///
+/// Closure that captures a reference to readable resources like block devices, memory buffers,
+/// network sockets, and more.
+///
+pub const Reader = meta.Function(@sizeOf(usize), []u8, usize);
+
 ///
 /// Returns a state machine for lazily computing all `Element` components of a given source input
 /// that match a delimiting pattern.
@@ -238,9 +244,9 @@ test "Null writing" {
 }
 
 ///
-/// Writes the singular `byte` to `writer`, returning `true` if it was successfully written,
+/// Applies the singular `byte` to `writer`, returning `true` if it was successfully written,
 /// otherwise `false`.
 ///
-pub fn writeByte(writer: Writer, byte: u8) bool {
+pub fn writeByte(writer: *Writer, byte: u8) bool {
     return (writer.apply(std.mem.asBytes(&byte)) != 0);
 }