You're seeing just the function next_char, go back to Ergo.Context module for more information.
Link to this function


Reads the next character from the input of the passed in Context.

If the input is empty returns status: {:error, :unexpected_eoi}.

Otherwise returns a new Context setting char to the character read and incrementing positional variables such as index, line, and column appropriately.


iex> Context.next_char( %Context{status: {:error, :unexpected_eoi}, message: "Unexpected end of input"}

iex> Context.next_char("Hello World")) %Context{status: :ok, input: "ello World", char: ?H, ast: ?H, index: 1, line: 1, col: 2}