Lua Parser Template

#!/opt/local/bin/lua
--
-- Simple parser
--

if not arg[1] then
    print "Need a filename as an argument."
    return
end

local f = io.open(arg[1], "rb")
local content = f:read("*all")
f:close()

context =
{
    content = content,
    cursor = 1,
    line_number = 1,
    column_number = 0,
    syntax_tree = {},

    Byte = function(self)
        return self.content:sub(self.cursor, self.cursor)
    end,

    AtEnd = function(self)
        return self.cursor == #self.content
    end,

    AdvanceCursor = function(self)

        self.cursor = self.cursor + 1
        if self.cursor > #self.content then
            print("Warning: Trying to advance past the end of the content.")
            self.cursor = #self.content
        end
        self.column_number = self.column_number + 1

        if self:Byte() == '\n' then
            self.line_number = self.line_number + 1
            self.column_number = 0
        end

    end
}

-- [1] Start by printing out the no lines in the file
-- [2] Make a gist at this point as it's quite a common op

while true do
    print(context:Byte())
    if context:AtEnd() then
        break
    else
        context:AdvanceCursor()
    end
end

print("Number of lines ", context.line_number)