Module:Format ISBN/sandbox explained

require ('strict');

local data = mw.loadData ('Module:Format ISBN/data'); -- fetch separator positioning data local hyphen_pos_t = data.hyphen_pos_t; -- the hyphen positioning data k/v table local index_t = data.index_t; -- an index sequence into the hyphen positioning data table; used by binary_search local idx_count = data.count; -- from count = #index_t; in ~/data; used by binary_search

----------------------------< B I N A R Y _ S E A R C H >----------------------------------------------------

do a binary search for the hyphen positioning data for in using its index sequence.

accepts one input (a string) which it converts to a number

returns index into as a number when proper formatting is found; nil else

local function binary_search (target_isbn) target_isbn = tonumber (target_isbn); -- convert to number because index_t[x] values are numbers

if (index_t[1] >= target_isbn) or (index_t[idx_count] < target_isbn) then -- invalid; out of range; 9780000000000 to whatever the last value is return; -- TODO: return something meaningful? end local idx_bot = 1; -- initialize to index 1 (first element in ) local idx_top = idx_count; -- initialize to index of last element in while idx_bot ~= idx_top do local idx_mid = math.ceil ((idx_bot + idx_top) / 2); -- get the mid-point in the index sequence if index_t[idx_mid] >= target_isbn then -- when mid-point index value is greater than or equal to the target isbn if index_t[idx_mid-1] < target_isbn then -- and when the preceding value is less than the target isbn return index_t[idx_mid]; -- we found the correct mapping for isbn; return index into end idx_top = idx_mid - 1; -- adjust else idx_bot = idx_mid; -- adjust end end mw.logObject ('didn\'t find formatting for isbn: ' .. target_isbn); -- just in case for the nonceend

----------------------------< C O N V E R T _ T O _ I S B N 1 0 >--------------------------------------------

convert 13-digit isbn to 10-digit isbn; removes 978 GS1 prefix and recalculates the check digit

takes a single input; the 13-digit isbn as a string without separators

assumes that the GS1 prefix is 978; there is no mapping between isbn10 and 979-prefixed isbn13. calling functionsare required to ensure that is a properly formed string of 13 digits (no separators) that begins with 978.

local function convert_to_isbn10 (isbn13) local isbn9 = isbn13:sub (4, 12); -- get the 9 digits of that follow the '978' GS1 prefix (drop the check digit)

local check = 0; -- initialize the check digit calculation local i = 1; -- index for j=10, 2, -1 do -- is weighting for each of the 9 digits; counting down, left to right check = check + tonumber (isbn9:sub (i, i)) * j; -- accumulate the sum the weighted-digit-products i = i + 1; -- bump the index end

check = check % 11; -- remainder of the weighted-digit-products divided by 11

if 0

check then return isbn9 .. '0'; -- special case else check = 11 - check; -- calculate the check digit return isbn9 .. ((10

check) and 'X' or check); -- when is ten, use 'X'; else endend

----------------------------< C O N V E R T _ T O _ I S B N 1 3 >--------------------------------------------

convert 10-digit isbn to 13-digit isbn; adds 978 GS1 prefix and recalculates the check digit

takes a single input; the 10-digit isbn as a string (no separators)

local function convert_to_isbn13 (isbn10) local isbn12 = '978'.. isbn10:sub(1, 9); -- concatenate '978' with first 9 digits of (drop the check digit) local check = 0; -- initialize the check digit calculation for i=1, 12 do -- for the first 12 digits ('978' and 9 others) check = check + tonumber (isbn12:sub (i, i)) * (3 - (i % 2) * 2); -- accumulate checksum end return isbn12 .. ((10 - (check % 10)) %10); -- extract check digit from checksum; append and doneend

--out=) on success; initial else

local function _format_isbn (isbn_str, show_err_msg, separator, output_format, template_name) if (not isbn_str) or (

isbn_str) then return ; -- empty or nil input? empty output end

local isbn_str_raw = isbn_str; -- this will be the return value if unable to format isbn_str = isbn_str:gsub ('[^%dX]', ); -- strip all formatting (spaces and hyphens) from the isbn/sbn

local flags = ; -- a convenient place for flag stuff if '13'

output_format then -- set a flag for output format; ignored when is an sbn flags.out13 = true; elseif '10'

output_format then flags.out10 = true; end

if 9

#isbn_str then -- looks like an sbn? isbn_str = '0' .. isbn_str; -- convert to isbn10 flags.sbn = true; -- set a flag end local err_msg = require ("Module:Check isxn").check_isbn ; -- does 'look' like a valid isbn? does not check ranging if ~= err_msg then -- when there is an error message if show_err_msg then -- and we are showing error messages return isbn_str_raw, err_msg; -- return our input and the message else return isbn_str_raw; -- not showing error messages; return our input without the message end end

if 13

#isbn_str and flags.out10 then -- if isbn13 but we want an isbn10 output flags.isbn10_check_digit = (convert_to_isbn10 (isbn_str)):sub (-1); -- calculate and extract the isbn10 check digit for later end if 10

#isbn_str then -- if isbn10 or sbn flags.isbn10_check_digit = isbn_str:sub (-1); -- extract the check digit for later isbn_str = convert_to_isbn13 (isbn_str); -- convert isbn10 to isbn13 for formatting end local index = binary_search (isbn_str); -- look for the formatting that applies to if index then -- if found local format_t = hyphen_pos_t[index]; -- get the formatting sequence local result_t = ; -- init with prefix; the GS1 prefix element ('978' or '979') local digit_ptr = 4; -- initialize to point at registration group element for _, n in ipairs (format_t) do -- loop through the formatting sequence to build a sequence of isbn13 elements table.insert (result_t, isbn_str:sub (digit_ptr, digit_ptr+n-1)); -- add the digits from [<digit_ptr>] to [<digit_ptr+n-1>] to sequence digit_ptr = digit_ptr + n; -- advance the digit pointer end table.insert (result_t, isbn_str:sub (13)); -- and add the check digit element to

isbn_str = table.concat (result_t, separator and ' ' or '-'); -- assemble formatted with space or hyphen (default) separators

if flags.isbn10_check_digit then -- if we saved the check digit from an sbn or isbn10 if flags.sbn then -- when input is an sbn isbn_str = isbn_str:gsub ('^978%-0%-', ):gsub ('%d$', flags.isbn10_check_digit); -- remove GS1 prefix element and registration group element; restore check digit else -- when input is an isbn10 if not flags.out13 then isbn_str = isbn_str:gsub ('^978%-', ):gsub ('%d$', flags.isbn10_check_digit); -- remove GS1 prefix element; restore check digit end end end

return isbn_str; -- return formatted end

return isbn_str_raw; -- should never actually be reached; but, if we do, return original input stringend

--2 template |isbn= params, no point in causing confusion due to multiple error messages

|separator=space – render formatted ISBN with spaces instead of hyphens |out= – takes either of 10 or 13 to specify the output format if different from the default

local function format_plain (frame) local args_t = require ('Module:Arguments').getArgs (frame); -- get template and invoke parameters local isbn_str = args_t[1]; local separator = 'space'

args_t.separator; -- boolean: when true use space separator; hyphen else local output_format = args_t.out; -- 10 or 13 to convert input format to the other for output

return _format_isbn (isbn_str, nil, separator, output_format); -- no error messagingend

--suppress-errors=yes – suppress error messages |separator=space – render formatted ISBN with spaces instead of hyphens |out= – takes either of 10 or 13 to specify the output format if different from the default

local function format_linked (frame) local args_t = require ('Module:Arguments').getArgs (frame); -- get template and invoke parameters local isbn_str = args_t[1]; local show_err_msg = 'yes' ~= args_t['suppress-errors']; -- always show errors unless |suppress-errors=yes local separator = 'space'

args_t.separator; -- boolean: when true use space separator; hyphen else local output_format = args_t.out; -- 10 or 13 to convert input format to the other for output

local formatted_isbn_str, err_msg = _format_isbn (isbn_str, show_err_msg, separator, output_format, args_t.template_name); -- show error messages unless suppressed if err_msg then return formatted_isbn_str .. ' ' .. err_msg; -- return unformatted, unlinked isbn and error message else return '' .. formatted_isbn_str ..''; -- return formatted and linked isbn endend

----------------------------< E X P O R T S >----------------------------------------------------------------

return