Module:String
This module is intended to provide access to basic string functions.
Most of the functions provided here can be invoked with named parameters, unnamed parameters, or a mixture. If named parameters are used, Mediawiki will automatically remove any leading or trailing whitespace from the parameter. Depending on the intended use, it may be advantageous to either preserve or remove such whitespace.
Global options
- ignore_errors
- If set to
lualua - error_category
- If an error occurs, specifies the name of a category to include with the error message. The default category is Errors reported by Module String.
- no_category
- If set to
lualua
local str = {}
-- Cannot include null byte.
local UTF8_char = "[\1-\127\194-\244][\128-\191]*"
--[[
ulen
Counts UTF-8 characters. Faster than mw.ustring.len.
Assumes that the encoding is correct. Unlike mw.ustring.len, does not return nil
if encoding is invalid.
Does not count the bytes 192, 193, and 245-255. They are not used in UTF-8 and
will not occur if the string is valid. They are replaced with the replacement
character (U+FFFD) on MediaWiki pages.
--]]
function str.ulen(text)
local _, length = string.gsub(text, UTF8_char, "")
return length
end
--[[
len
This function returns the length of the target string.
Usage:
{{#invoke:string|len|target_string|}}
OR
{{#invoke:string|len|s=target_string}}
Parameters
s: The string whose length to report
If invoked using named parameters, Mediawiki will automatically remove any leading or
trailing whitespace from the target string.
]]
function str.len(frame)
local new_args = str._getParameters(frame.args, { 's' });
local s = new_args['s'] or '';
return mw.ustring.len(s)
end
--[[
sub
This function returns a substring of the target string at specified indices.
Usage:
{{#invoke:string|sub|target_string|start_index|end_index}}
OR
{{#invoke:string|sub|s=target_string|i=start_index|j=end_index}}
Parameters
s: The string to return a subset of
i: The fist index of the substring to return, defaults to 1.
j: The last index of the string to return, defaults to the last character.
The first character of the string is assigned an index of 1. If either i or j
is a negative value, it is interpreted the same as selecting a character by
counting from the end of the string. Hence, a value of -1 is the same as
selecting the last character of the string.
If the requested indices are out of range for the given string, an error is
reported.
]]
function str.sub(frame)
local new_args = str._getParameters(frame.args, { 's', 'i', 'j' });
local s = new_args['s'] or '';
local i = tonumber(new_args['i']) or 1;
local j = tonumber(new_args['j']) or -1;
local len = mw.ustring.len(s);
-- Convert negatives for range checking
if i < 0 then
i = len + i + 1;
end
if j < 0 then
j = len + j + 1;
end
if i > len or j > len or i < 1 or j < 1 then
return str._error('String subset index out of range');
end
if j < i then
return str._error('String subset indices out of order');
end
return mw.ustring.sub(s, i, j)
end
--[[
This function implements that features of {{str sub old}} and is kept in order
to maintain these older templates.
]]
function str.sublength(frame)
local i = tonumber(frame.args.i) or 0
local len = tonumber(frame.args.len)
return mw.ustring.sub(frame.args.s, i + 1, len and (i + len))
end
--[[
match
This function returns a substring from the source string that matches a
specified pattern.
Usage:
{{#invoke:string|match|source_string|pattern_string|start_index|match_number|plain_flag|nomatch_output}}
OR
{{#invoke:string|pos|s=source_string|pattern=pattern_string|start=start_index
|match=match_number|plain=plain_flag|nomatch=nomatch_output}}
Parameters
s: The string to search
pattern: The pattern or string to find within the string
start: The index within the source string to start the search. The first
character of the string has index 1. Defaults to 1.
match: In some cases it may be possible to make multiple matches on a single
string. This specifies which match to return, where the first match is
match= 1. If a negative number is specified then a match is returned
counting from the last match. Hence match = -1 is the same as requesting
the last match. Defaults to 1.
plain: A flag indicating that the pattern should be understood as plain
text. Defaults to false.
nomatch: If no match is found, output the "nomatch" value rather than an error.
If invoked using named parameters, Mediawiki will automatically remove any leading or
trailing whitespace from each string. In some circumstances this is desirable, in
other cases one may want to preserve the whitespace.
If the match_number or start_index are out of range for the string being queried, then
this function generates an error. An error is also generated if no match is found.
If one adds the parameter ignore_errors=true, then the error will be suppressed and
an empty string will be returned on any failure.
For information on constructing Lua patterns, a form of [regular expression], see:
* http://www.lua.org/manual/5.1/manual.html#5.4.1
* http://www.mediawiki.org/wiki/Extension:Scribunto/Lua_reference_manual#Patterns
* http://www.mediawiki.org/wiki/Extension:Scribunto/Lua_reference_manual#Ustring_patterns
]]
function str.match(frame)
local new_args = str._getParameters(frame.args, { 's', 'pattern', 'start', 'match', 'plain', 'nomatch' });
local s = new_args['s'] or '';
local start = tonumber(new_args['start']) or 1;
local plain_flag = str._getBoolean(new_args['plain'] or false);
local pattern = new_args['pattern'] or '';
local match_index = math.floor(tonumber(new_args['match']) or 1);
local nomatch = new_args['nomatch'];
if s == '' then
return str._error('Target string is empty');
end
if pattern == '' then
return str._error('Pattern string is empty');
end
if math.abs(start) < 1 or math.abs(start) > mw.ustring.len(s) then
return str._error('Requested start is out of range');
end
if match_index == 0 then
return str._error('Match index is out of range');
end
if plain_flag then
pattern = str.pattern_escape(pattern);
end
local result
if match_index == 1 then
-- Find first match is simple case
result = mw.ustring.match(s, pattern, start)
else
if start > 1 then
s = mw.ustring.sub(s, start);
end
local iterator = mw.ustring.gmatch(s, pattern);
if match_index > 0 then
-- Forward search
for w in iterator do
match_index = match_index - 1;
if match_index == 0 then
result = w;
break;
end
end
else
-- Reverse search
local result_table = {};
local count = 1;
for w in iterator do
result_table[count] = w;
count = count + 1;
end
result = result_table[count + match_index];
end
end
if result == nil then
if nomatch == nil then
return str._error('Match not found');
else
return nomatch;
end
else
return result;
end
end
--[[
pos
This function returns a single character from the target string at position pos.
Usage:
{{#invoke:string|pos|target_string|index_value}}
OR
{{#invoke:string|pos|target=target_string|pos=index_value}}
Parameters
target: The string to search
pos: The index for the character to return
If invoked using named parameters, Mediawiki will automatically remove any leading or
trailing whitespace from the target string. In some circumstances this is desirable, in
other cases one may want to preserve the whitespace.
The first character has an index value of 1.
If one requests a negative value, this function will select a character by counting backwards
from the end of the string. In other words pos = -1 is the same as asking for the last character.
A requested value of zero, or a value greater than the length of the string returns an error.
]]
function str.pos(frame)
local new_args = str._getParameters(frame.args, { 'target', 'pos' });
local target_str = new_args['target'] or '';
local pos = tonumber(new_args['pos']) or 0;
if pos == 0 or math.abs(pos) > mw.ustring.len(target_str) then
return str._error('String index out of range');
end
return mw.ustring.sub(target_str, pos, pos);
end
--[[
str_find
This function duplicates the behavior of {{str_find}}, including all of its quirks.
This is provided in order to support existing templates, but is NOT RECOMMENDED for
new code and templates. New code is recommended to use the "find" function instead.
Returns the first index in "source" that is a match to "target". Indexing is 1-based,
and the function returns -1 if the "target" string is not present in "source".
Important Note: If the "target" string is empty / missing, this function returns a
value of "1", which is generally unexpected behavior, and must be accounted for
separatetly.
]]
function str.str_find(frame)
local new_args = str._getParameters(frame.args, { 'source', 'target' });
local source_str = new_args['source'] or '';
local target_str = new_args['target'] or '';
if target_str == '' then
return 1;
end
local start = mw.ustring.find(source_str, target_str, 1, true)
if start == nil then
start = -1
end
return start
end
--[[
find
This function allows one to search for a target string or pattern within another
string.
Usage:
{{#invoke:string|find|source_str|target_string|start_index|plain_flag}}
OR
{{#invoke:string|find|source=source_str|target=target_str|start=start_index|plain=plain_flag}}
Parameters
source: The string to search
target: The string or pattern to find within source
start: The index within the source string to start the search, defaults to 1
plain: Boolean flag indicating that target should be understood as plain
text and not as a Lua style regular expression, defaults to true
If invoked using named parameters, Mediawiki will automatically remove any leading or
trailing whitespace from the parameter. In some circumstances this is desirable, in
other cases one may want to preserve the whitespace.
This function returns the first index >= "start" where "target" can be found
within "source". Indices are 1-based. If "target" is not found, then this
function returns an empty string. If either "source" or "target" are missing / empty, this
function also returns an empty string.
This function should be safe for UTF-8 strings.
]]
function str.find(frame)
local params = {
[1] = { required = true },
[2] = { required = true },
[3] = { type = "number" },
[4] = { type = "boolean" },
}
local args = require("Module:parameters").process(frame.args, params)
return mw.ustring.find(args[1], args[2], args[3], args[4])
end
--[[
replace
This function allows one to replace a target string or pattern within another
string.
Usage:
{{#invoke:string|replace|source_str|pattern_string|replace_string|replacement_count|plain_flag}}
OR
{{#invoke:string|replace|source=source_string|pattern=pattern_string|replace=replace_string|
count=replacement_count|plain=plain_flag}}
Parameters
source: The string to search
pattern: The string or pattern to find within source
replace: The replacement text
count: The number of occurences to replace, defaults to all.
plain: Boolean flag indicating that pattern should be understood as plain
text and not as a Lua style regular expression, defaults to true
]]
function str.replace(frame)
local new_args = str._getParameters(frame.args, { 'source', 'pattern', 'replace', 'count', 'plain' });
local source_str = new_args['source'] or '';
local pattern = new_args['pattern'] or '';
local replace = new_args['replace'] or '';
local count = tonumber(new_args['count']);
local plain = new_args['plain'] or true;
if source_str == '' or pattern == '' then
return source_str;
end
plain = str._getBoolean(plain);
if plain then
pattern = str.pattern_escape(pattern);
replace = mw.ustring.gsub(replace, "%%", "%%%%"); --Only need to escape replacement sequences.
end
local result;
result = mw.ustring.gsub(source_str, pattern, replace, count);
return result;
end
function str.gsub(frame)
local params = {
[1] = { required = true, allow_empty = true },
[2] = { required = true, allow_empty = true },
[3] = { required = true, allow_empty = true },
[4] = { type = "number" },
}
local args = require("Module:parameters").process(frame.args, params)
return (mw.ustring.gsub(args[1], args[2], args[3], args[4]))
end
--[[
simple function to pipe string.rep to templates.
]]
function str.rep(frame)
local repetitions = tonumber(frame.args[2])
if not repetitions then
return str._error('function rep expects a number as second parameter, received "' .. (frame.args[2] or '') .. '"')
end
return string.rep(frame.args[1] or '', repetitions)
end
function str.lower(frame)
local text = frame.args[1] or ''
return mw.ustring.lower(text)
end
str.lc = str.lower
--[[
Helper function that populates the argument list given that user may need to use a mix of
named and unnamed parameters. This is relevant because named parameters are not
identical to unnamed parameters due to string trimming, and when dealing with strings
we sometimes want to either preserve or remove that whitespace depending on the application.
]]
function str._getParameters(frame_args, arg_list)
local new_args = {};
local index = 1;
local value;
for _, arg in ipairs(arg_list) do
value = frame_args[arg]
if value == nil then
value = frame_args[index];
index = index + 1;
end
new_args[arg] = value;
end
return new_args;
end
--[[
Helper function to handle error messages.
]]
function str._error(error_str)
local frame = mw.getCurrentFrame();
local error_category = frame.args.error_category or 'Errors reported by Module String';
local ignore_errors = frame.args.ignore_errors or false;
local no_category = frame.args.no_category or false;
if str._getBoolean(ignore_errors) then
return '';
end
local error_str = '<strong class="error">String Module Error: ' .. error_str .. '</strong>';
if error_category ~= '' and not str._getBoolean(no_category) then
error_str = '[[Category:' .. error_category .. ']]' .. error_str;
end
return error_str;
end
--[[
Helper Function to interpret boolean strings
]]
function str._getBoolean(boolean_str)
local boolean_value;
if type(boolean_str) == 'string' then
boolean_str = boolean_str:lower();
if boolean_str == 'false' or boolean_str == 'no' or boolean_str == '0'
or boolean_str == '' then
boolean_value = false;
else
boolean_value = true;
end
elseif type(boolean_str) == 'boolean' then
boolean_value = boolean_str;
else
error('No boolean value found');
end
return boolean_value
end
--[[
Helper function that escapes all pattern characters – ().%+-*?[^$] – so that they will be treated
as plain text.
]]
function str.pattern_escape(pattern_str)
local invoked = false
if type(pattern_str) == "table" then
if pattern_str.args then
local frame = pattern_str
invoked = true
if frame.args[1] then
pattern_str = frame.args[1]
else
pattern_str = frame:getParent().args[1]
end
else
error("First argument to pattern_escape should be a string, a number, or a frame object.")
end
elseif not (type(pattern_str) == "string" or type(pattern_str) == "number") then
error("First argument to pattern_escape should be a string or a number.")
end
if invoked then
local escaped = mw.ustring.gsub(pattern_str, "([%(%)%.%%%+%-%*%?%[%^%$%]])", "%%%1")
return escaped
else
return mw.ustring.gsub(pattern_str, "([%(%)%.%%%+%-%*%?%[%^%$%]])", "%%%1");
end
end
function str.count(text, pattern, plain)
if not (type(text) == "string" or type(text) == "number") then
error('The first argument to the function "count" must be a string or a number, not a ' .. type(text) .. '.')
end
if not (type(pattern) == "string" or type(pattern) == "number") then
error('The first argument to the function "count" must be a string or a number, not a ' .. type(text) .. '.')
end
if plain then
pattern = str.pattern_escape(pattern)
end
local _, count = mw.ustring.gsub(text, pattern, "")
return count
end
function str.plain_gsub(text, pattern, replacement)
local invoked = false
if type(text) == "table" then
invoked = true
if text.args then
local frame = text
local params = {
[1] = {},
[2] = {},
[3] = { allow_empty = true },
}
local args = require("Module:parameters").process(frame.args, params)
text = args[1]
pattern = args[2]
replacement = args[3]
else
error("If the first argument to plain_gsub is a table, it should be a frame object.")
end
else
if not (type(pattern) == "string" or type(pattern) == "number") then
error("The second argument to plain_gsub should be a string or a number.")
end
if not (type(replacement) == "string" or type(replacement) == "number") then
error("The third argument to plain_gsub should be a string or a number.")
end
end
pattern = str.pattern_escape(pattern)
if invoked then
text = mw.ustring.gsub(text, pattern, replacement)
return text
else
return mw.ustring.gsub(text, pattern, replacement)
end
end
function str.matchToArray(text, pattern)
local invoked = false
if type(text) == "table" then
invoked = true
if text.args then
local frame = text
local params = {
[1] = { required = true },
[2] = { required = true },
}
local args = require("Module:parameters").process(frame.args, params)
text = args[1]
pattern = args[2]
else
error("If the first argument to matchToArray is a table, it should be a frame object.")
end
else
if not (type(pattern) == "string" or type(pattern) == "number") then
error("The second argument to matchToArray should be a string or a number.")
end
end
local matches = {}
local i = 0
for match in mw.ustring.gmatch(text, pattern) do
i = i + 1
matches[i] = match
end
if i > 0 then
if invoked then
return table.concat(matches, ", ")
else
return matches
end
else
if invoked then
return ""
else
return nil
end
end
end
--[=[
Similar to gmatch, but it returns the count of the match in addition to the
list of captures, something like ipairs().
If the pattern doesn't contain any captures, the whole match is returned.
Invoke thus:
for i, whole_match in require("Module:string").imatch(text, pattern) do
[ do something with i and whole_match ]
end
or
for i, capture1[, capture2[, capture3[, ...]]] in require("Module:string").imatch(text, pattern) do
[ do something with i and capture1 ]
end
For example, this code
for i, whole_match in require("Module:string").imatch("a b c", "[a-z]") do
mw.log(i, whole_match)
end
will log
1 a
2 b
3 c
]=]
function str.imatch(text, pattern, pos, plain, use_basic_Lua_function)
local i = 0
pos = pos or 0
if not string.find(pattern, "%b()") then
pattern = "(" .. pattern .. ")"
end
local find = use_basic_Lua_function and string.find or mw.ustring.find
return function()
i = i + 1
local return_values = { find(text, pattern, pos, plain) }
local j = return_values[2]
if return_values[3] then
pos = j + 1
-- Skip the first two returned values, which are the indices of the
-- whole match.
return i, unpack(return_values, 3)
end
end
end
function str.escapebytes(s)
return (string.gsub(s,
'.',
function(char)
return ('\\%03d'):format(string.byte(char))
end))
end
function str.URIdecode(frame)
return mw.uri.decode(frame.args[1], frame.args[2] or "PATH")
end
return str