diff --git a/common.lua b/common.lua
index 15571de..2395513 100644
--- a/common.lua
+++ b/common.lua
@@ -30,6 +30,7 @@ local function iterate_utf8_chars (str)
 end
 
 local function utf8_string_length (str)
+	assert(type(str) == 'string')
 	local len = 0
 	for char in iterate_utf8_chars(str) do
 		if not UNICODE_ZERO_WIDTH_CHARACTERS[char] then
diff --git a/pretty.lua b/pretty.lua
index 7b45b3a..53de8ce 100644
--- a/pretty.lua
+++ b/pretty.lua
@@ -72,12 +72,17 @@ local ERROR_UNKNOWN_TYPE = [[
 We are attempting to cover all Lua features, so please report this bug, so we can improve.
 ]]
 
+local TERMINAL_WIDTH = 80
 local MAX_WIDTH_FOR_SINGLE_LINE_TABLE = 38
+
 if io and io.popen then
     local f = io.popen "tput cols"
     local term_width = f:read '*n'
     f:close()
---    if term_width then  MAX_WIDTH_FOR_SINGLE_LINE_TABLE = term_width * 3 / 2  end
+    if term_width then
+        TERMINAL_WIDTH = term_width
+        --MAX_WIDTH_FOR_SINGLE_LINE_TABLE = term_width * (2 / 3)
+    end
 end
 
 local KEY_TYPE_SORT_ORDER = {
@@ -313,7 +318,7 @@ local function align_into_columns (l, start_i, stop_i)
     for nr_items_pr_row = 10, 1, -1 do  -- TODO: Do this more intelligently.
         local column_width
         column_width, columns  =  attempt_to_align_into_columns(l, start_i, stop_i, nr_items_pr_row)
-        if column_width <= MAX_WIDTH_FOR_SINGLE_LINE_TABLE then  break  end
+        if column_width <= l.options.max_width_for_single_line_table then  break  end
     end
 
     -- Change alignment of columns
@@ -501,12 +506,14 @@ local function format_table (t, display, l, format_value)
 
     -- Decide for short or long table formatting.
     local table_width  =  width_of_strings_in_l(l, start_of_table_i)
-    if table_width <= MAX_WIDTH_FOR_SINGLE_LINE_TABLE then
+
+    if table_width <= l.options.max_width_for_single_line_table then
         -- Is short table: Ignore "width of key".
         l[start_of_table_i][3] = 'inline'
         ignore_alignment_info(l, start_of_table_i)
     elseif table_info.is_leaf_node then
         -- Is leaf node: Can format into columns.
+        -- Only if long or sequence.
         -- NOTE: Currently we only allow leaf-nodes to format into columns, due
         -- to issues with table alignment.
         align_into_columns(l, start_of_table_i)
@@ -562,7 +569,6 @@ local TYPE_TO_FORMAT_FUNC = {
 local function format_value (value, display, l)
     assert(type(display) == 'number' and type(l) == 'table')
     local formatting = TYPE_TO_FORMAT_FUNC[type(value)]
-    --print(value, formatting)
     if formatting then
         formatting(value, display, l, format_value)
     else
@@ -588,6 +594,8 @@ local KNOWN_OPTIONS = {
     _table_addr_comment = { type = 'boolean', default = false, debug = 'debug' }, -- TODO: Maybe automatically display table address when display = 0?
 
     indent              = { type = 'string',  default = '    ' },
+
+    max_output_width    = { type = 'number',  default = TERMINAL_WIDTH }
 }
 
 local function ensure_that_all_options_are_known (input_options)
@@ -622,10 +630,36 @@ local function ensure_that_all_options_are_known (input_options)
             output_options[option_name] = option_info.default
         end
     end
+    -- Calculate derived settings
+    output_options.max_width_for_single_line_table = MAX_WIDTH_FOR_SINGLE_LINE_TABLE -- TODO: Make dynamic
+
     -- Returns input_options
     return output_options
 end
 
+local function length_of_longest_line_in_text (text)
+    assert(type(text) == 'string')
+    local longest_line_len = text:match '([^\n]*)$' : len()
+    for line in text:gmatch '(.-)\n' do
+        longest_line_len = math.max(longest_line_len, line:len())
+    end
+    return longest_line_len
+end
+
+local function internal_warning (fmt, ...)
+    io.stderr:write('[pretty/internal]: '..string.format(fmt, ...))
+end
+
+local function assert_pretty_result (repr, options)
+    assert(type(repr) == 'string')
+    assert(type(options) == 'table')
+    -- Determine length of longest line in output
+    local max_width = length_of_longest_line_in_text(repr)
+    if max_width > options.max_output_width then
+        internal_warning('Internal assertion failed. Width of output was %i, but should be less than %i.', max_width, options.max_output_width)
+    end
+end
+
 local function pretty_format (value, options)
     -- Error checking
     local options  =  ensure_that_all_options_are_known(options or {})
@@ -642,7 +676,12 @@ local function pretty_format (value, options)
     fix_seperator_info(l, l.options.indent)
     ignore_alignment_info(l)
 
-    return table.concat(l, '')
+    -- Concat and perform last assertions.
+    local repr = table.concat(l, '')
+    assert_pretty_result(repr, options)
+
+    -- Return
+    return repr
 end
 
 return pretty_format
diff --git a/test/test_pretty.lua b/test/test_pretty.lua
index be40791..e9f7438 100644
--- a/test/test_pretty.lua
+++ b/test/test_pretty.lua
@@ -34,6 +34,15 @@ local function format_test (t)
     end, { line = debug.getinfo(2).currentline })
 end
 
+local function format_parsable_test (t)
+    local stripped = t.text:match '^%s*(.-)%s*$'
+    return format_test {
+        name   = t.name,
+        input  = loadstring('return '..stripped)(),
+        expect = stripped
+    }
+end
+
 --------------------------------------------------------------------------------
 -- Primitive types
 
@@ -263,6 +272,16 @@ format_test {
     expect = '{\n    \'hello\', \'world\',       \'how\',\n    \'is\',    \'it\',          \'going?\',\n    \'Im\',    \'doing great\', \'thanks\',\n    \'that\',  \'was\',         \'what\',\n    \'I\'\n}',
 }
 
+format_parsable_test {
+    name = 'Column style with aligned numbers',
+    text = [[
+{
+    200, -522, 423, 516, 523, 126, 2912,
+    523, -620,   0,   0,   0,  -5,    2,
+     72,    6
+}
+]] }
+
 format_test {
 	name = 'Tabular style with strings left aligned',
     input  = {