Module:String

The String script wraps select functions of the Ustring library. Usage:

{{#invoke:String|FUNCTION|ARG1|ARG2…}}

Character positions within a string are indexed from 1, not zero. The following call to function sub would, for instance, return the substring "ham".

{{#invoke:String|sub|hamburger|1|3}}

The functions listed below are wrapped and made available. The links are to the String version documentation. These in turn link to the less informative Ustring versions, which are always the ones actually wrapped here.

• find - Differs from the library version in three ways: 1) defaults the 'plain' argument to true; 2) returns the index at which the pattern is found, otherwise zero; and 3) always returns zero when called with an empty string or pattern.
• gsub
• len
• sub

The following additional functions are declared. See the code below for usage instructions.

• charAt

---

-- Cf. https://en.wikipedia.org/wiki/Module:String
--
local p = {}



------------------------------------------------------------------------------------------
-- charAt - return the character at index C
--
--    charAt(S,C)
--
function p.charAt( frame )
    local c = tonumber( frame.args[2] )
    return mw.ustring.sub( frame.args[1], c, c )
    end



------------------------------------------------------------------------------------------
-- find
--
-- Differs from the library version in three ways: 1) defaults the 'plain' argument to true;
-- 2) returns the index at which the pattern is found, otherwise zero; and 3) always returns
-- zero when called with an empty string or pattern.
--
-- Modified from https://en.wikipedia.org/wiki/Module:String
--
function p.find( frame )
    local s = frame.args[1]
    local pattern = frame.args[2]
    if s == '' or pattern == '' then
        return 0
        end

    local plain = frame.args[4]
    if plain == nil then
        plain = true
    else
        plain = toBoolean( plain )
        end
    local start = mw.ustring.find( s, pattern, tonumber(frame.args[3]), plain )
    if start == nil then
        start = 0
        end
    return start
    end



------------------------------------------------------------------------------------------
function p.gsub( frame )
    local result = mw.ustring.gsub( frame.args[1], frame.args[2], frame.args[3], tonumber(frame.args[4]) ) -- ignoring 2nd return value (count)
    return result
    end



------------------------------------------------------------------------------------------
function p.len( frame )
    return mw.ustring.len( frame.args[1] )
    end



------------------------------------------------------------------------------------------
function p.sub( frame )
    return mw.ustring.sub( frame.args[1], tonumber(frame.args[2]), tonumber(frame.args[3]) )
    end



------------------------------------------------------------------------------------------
-- toBoolean - translate a MediaWiki string to a Lua boolean
--
-- Modified from https://en.wikipedia.org/wiki/Module:String
--
function toBoolean( s )
    local b;
    if s == nil then
        b = false;
    else
        local sType = type( s )
        if sType == 'string' then
            s = s:lower();
            b = s ~= 'false' and s ~= 'no' and s ~= '0' and s ~= ''
        elseif sType == 'boolean' then
            b = s;
        else
            error( 'Not a boolean value' )
            end
        end
    return b
    end



return p