--[[  This code is derived from the ISXN validation code at Module:Citation/CS1.  It allows validating ISBN, ISMN, and ISSN without invoking a citation template.  ]]  local p = {}  --[[--------------------------< E R R _ M S G _ S U P L _ T >--------------------------------------------------  error message supplements for check_isbn(); adapted from a similarly named table at Module:Citation/CS1/Configuration  ]]  local err_msg_supl_t = { 	['char'] = 'অবৈধ অক্ষর', 	['check'] = 'চেকসাম', 	['form'] = 'অবৈধ ফর্ম', 	['group'] = 'অবৈধ গ্রুপ আইডি', 	['length'] = 'দৈর্ঘ্য', 	['prefix'] = 'অবৈধ উপসর্গ', 	}  --[[--------------------------< IS _ V A L I D _ I S X N >-----------------------------------------------------  ISBN-10 and ISSN validator code calculates checksum across all isbn/issn digits including the check digit. ISBN-13 is checked in check_isbn(). If the number is valid the result will be 0. Before calling this function, issbn/issn must be checked for length and stripped of dashes, spaces and other non-isxn characters.  ]]  local function is_valid_isxn (isxn_str, len) 	local temp = 0; 	isxn_str = { isxn_str:byte(1, len) };	-- make a table of byte values '0' → 0x30 .. '9'  → 0x39, 'X' → 0x58 	len = len+1;							-- adjust to be a loop counter 	for i, v in ipairs( isxn_str ) do		-- loop through all of the bytes and calculate the checksum 		if v == string.byte( "X" ) then		-- if checkdigit is X (compares the byte value of 'X' which is 0x58) 			temp = temp + 10*( len - i );	-- it represents 10 decimal 		else 			temp = temp + tonumber( string.char(v) )*(len-i); 		end 	end 	return temp % 11 == 0;					-- returns true if calculation result is zero end  --[[--------------------------< IS _ V A L I D _ I S X N  _ 1 3 >----------------------------------------------  ISBN-13 and ISMN validator code calculates checksum across all 13 isbn/ismn digits including the check digit. If the number is valid, the result will be 0. Before calling this function, isbn-13/ismn must be checked for length and stripped of dashes, spaces and other non-isxn-13 characters.  ]]  local function is_valid_isxn_13 (isxn_str) 	local temp=0; 	 	isxn_str = { isxn_str:byte(1, 13) };										-- make a table of byte values '0' → 0x30 .. '9'  → 0x39 	for i, v in ipairs( isxn_str ) do 		temp = temp + (3 - 2*(i % 2)) * tonumber( string.char(v) );				-- multiply odd index digits by 1, even index digits by 3 and sum; includes check digit 	end 	return temp % 10 == 0;														-- sum modulo 10 is zero when isbn-13/ismn is correct end  --[[--------------------------< C H E C K _ I S B N >------------------------------------------------------------  Determines whether an ISBN string is valid.  Implements an ISBN validity check for , , , and .  ]]  local function check_isbn (isbn_str, frame) 	local function return_result (check, err_type)								-- local function to render the various error returns 		if not check then														-- <check> false when there is an error 			local template = ((frame.args.template_name and  ~= frame.args.template_name) and frame.args.template_name) or nil;	-- get template name 			if not template then 				return ' কলিং টেমপ্লেটের template_name প্যারামিটার প্রয়োজন'; 			end  			local out_t = {''};		-- open the error message span 			table.insert (out_t, ' {{[[টেমপ্লেট:');		-- open 'template' markup; open wikilink with Template namespace 			table.insert (out_t, template);										-- template name wikilink 			table.insert (out_t, '|');											-- its pipe 			table.insert (out_t, template);										-- wikilink label 			table.insert (out_t, ']]}} এ প্যারামিটার ত্রুটি: ');								-- close wikilink; close 'template' markup 			table.insert (out_t, err_type);										-- type of isbn error 			table.insert (out_t, '')										-- close the error message span 			if 0 == mw.title.getCurrentTitle().namespace then					-- categorize only when this template is used in mainspace 				local category = table.concat ({'বিষয়শ্রেণী:আইএসবিএন ত্রুটিসহ পাতা'}); 				table.insert (out_t, category); 			end 			return table.concat (out_t);										-- make a big string and done 		end 	return ;																	-- no error, return an empty string 	end  	if nil ~= isbn_str:match ('[^%s-0-9X]') then 		return return_result (false, err_msg_supl_t.char);						-- fail if isbn_str contains anything but digits, hyphens, or the uppercase X 	end  	local id = isbn_str:gsub ('[%s-]', );										-- remove hyphens and whitespace  	local len = id:len();   	if len ~= 10 and len ~= 13 then 		return return_result (false, err_msg_supl_t.length);					-- fail if incorrect length 	end  	if len == 10 then 		if id:match ('^%d*X?$') == nil then										-- fail if isbn_str has 'X' anywhere but last position 			return return_result (false, err_msg_supl_t.form);									 		end 		if id:find ('^63[01]') then												-- 630xxxxxxx and 631xxxxxxx are (apparently) not valid isbn group ids but are used by amazon as numeric identifiers (asin) 			return return_result (false, err_msg_supl_t.group);					-- fail if isbn-10 begins with 630/1 		end 		return return_result (is_valid_isxn (id, 10), err_msg_supl_t.check);	-- pass if isbn-10 is numerically valid (checksum) 	else 		if id:match ('^%d+$') == nil then 			return return_result (false, err_msg_supl_t.char);					-- fail if ISBN-13 is not all digits 		end 		if id:match ('^97[89]%d*$') == nil then 			return return_result (false, err_msg_supl_t.prefix);				-- fail when ISBN-13 does not begin with 978 or 979 		end 		if id:match ('^9790') then 			return return_result (false, err_msg_supl_t.group);					-- group identifier '0' is reserved to ISMN 		end 		return return_result (is_valid_isxn_13 (id), err_msg_supl_t.check);		-- pass if isbn-10 is numerically valid (checksum) 	end end  --[[--------------------------< C H E C K _ I S M N >------------------------------------------------------------  Determines whether an ISMN string is valid.  Similar to isbn-13, ismn is 13 digits begining 979-0-... and uses the same check digit calculations.  See http://www.ismn-international.org/download/Web_ISMN_Users_Manual_2008-6.pdf section 2, pages 9–12.  ]]  local function check_ismn (id, error_string) 	local text; 	local valid_ismn = true;  	id=id:gsub( "[%s-–]", "" );													-- strip spaces, hyphens, and endashes from the ismn  	if 13 ~= id:len() or id:match( "^9790%d*$" ) == nil then					-- ismn must be 13 digits and begin 9790 		valid_ismn = false; 	else 		valid_ismn=is_valid_isxn_13 (id);										-- validate ismn 	end  	return valid_ismn and  or error_string end  --[[--------------------------< I S S N >----------------------------------------------------------------------  Validate and format an issn.  This code fixes the case where an editor has included an ISSN in the citation but has separated the two groups of four digits with a space.  When that condition occurred, the resulting link looked like this:  	|issn=0819 4327 gives: 4327 0819 4327  -- can't have spaces in an external link 	 This code now prevents that by inserting a hyphen at the issn midpoint.  It also validates the issn for length and makes sure that the checkdigit agrees with the calculated value.  Incorrect length (8 digits), characters other than 0-9 and X, or checkdigit / calculated value mismatch will all cause a check issn error message.  ]]  local function check_issn(id, error_string) 	local issn_copy = id;		-- save a copy of unadulterated issn; use this version for display if issn does not validate 	local text; 	local valid_issn = true;  	if not id:match ('^%d%d%d%d%-%d%d%d[%dX]$') then 		return error_string; 	end 	 	id=id:gsub( "[%s-–]", "" );									-- strip spaces, hyphens, and endashes from the issn  	if 8 ~= id:len() or nil == id:match( "^%d*X?$" ) then		-- validate the issn: 8 digits long, containing only 0-9 or X in the last position 		valid_issn=false;										-- wrong length or improper character 	else 		valid_issn=is_valid_isxn(id, 8);						-- validate issn 	end  	return valid_issn and '' or error_string end  < E N T R Y   P O I N T S >--------------------------------------------------====  function p.check_isbn(frame) 	return check_isbn(frame.args[1] or frame:getParent().args[1], frame) end  function p.check_ismn(frame) 	return check_ismn(frame.args[1] or frame:getParent().args[1], frame.args['error'] or frame:getParent().args['error'] or 'error') end  function p.check_issn(frame) 	return check_issn(frame.args[1] or frame:getParent().args[1], frame.args['error'] or frame:getParent().args['error'] or 'error') end  return p