path: root/lualibs-util-str.lua

if not modules then modules = { } end modules ['util-str'] = {
    version   = 1.001,
    comment   = "companion to luat-lib.mkiv",
    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
    copyright = "PRAGMA ADE / ConTeXt Development Team",
    license   = "see context related readme files"
}

utilities         = utilities or {}
utilities.strings = utilities.strings or { }
local strings     = utilities.strings

local format, gsub, rep, sub = string.format, string.gsub, string.rep, string.sub
local load, dump = load, string.dump
local tonumber, type, tostring = tonumber, type, tostring
local unpack, concat = table.unpack, table.concat
local P, V, C, S, R, Ct, Cs, Cp, Carg, Cc = lpeg.P, lpeg.V, lpeg.C, lpeg.S, lpeg.R, lpeg.Ct, lpeg.Cs, lpeg.Cp, lpeg.Carg, lpeg.Cc
local patterns, lpegmatch = lpeg.patterns, lpeg.match
local utfchar, utfbyte = utf.char, utf.byte
----- loadstripped = utilities.lua.loadstripped
----- setmetatableindex = table.setmetatableindex

local loadstripped = _LUAVERSION < 5.2 and load or function(str)
    return load(dump(load(str),true)) -- it only makes sense in luajit and luatex where we have a stipped load
end

-- todo: make a special namespace for the formatter

if not number then number = { } end -- temp hack for luatex-fonts

local stripper = patterns.stripzeros

local function points(n)
    return (not n or n == 0) and "0pt" or lpegmatch(stripper,format("%.5fpt",n/65536))
end

local function basepoints(n)
    return (not n or n == 0) and "0bp" or lpegmatch(stripper,format("%.5fbp", n*(7200/7227)/65536))
end

number.points     = points
number.basepoints = basepoints

-- str = " \n \ntest  \n test\ntest "
-- print("["..string.gsub(string.collapsecrlf(str),"\n","+").."]")

local rubish     = patterns.spaceortab^0 * patterns.newline
local anyrubish  = patterns.spaceortab + patterns.newline
local anything   = patterns.anything
local stripped   = (patterns.spaceortab^1 / "") * patterns.newline
local leading    = rubish^0 / ""
local trailing   = (anyrubish^1 * patterns.endofstring) / ""
local redundant  = rubish^3 / "\n"

local pattern = Cs(leading * (trailing + redundant + stripped + anything)^0)

function strings.collapsecrlf(str)
    return lpegmatch(pattern,str)
end

-- The following functions might end up in another namespace.

local repeaters = { } -- watch how we also moved the -1 in depth-1 to the creator

function strings.newrepeater(str,offset)
    offset = offset or 0
    local s = repeaters[str]
    if not s then
        s = { }
        repeaters[str] = s
    end
    local t = s[offset]
    if t then
        return t
    end
    t = { }
    setmetatable(t, { __index = function(t,k)
        if not k then
            return ""
        end
        local n = k + offset
        local s = n > 0 and rep(str,n) or ""
        t[k] = s
        return s
    end })
    s[offset] = t
    return t
end

-- local dashes = strings.newrepeater("--",-1)
-- print(dashes[2],dashes[3],dashes[1])

local extra, tab, start = 0, 0, 4, 0

local nspaces = strings.newrepeater(" ")

string.nspaces = nspaces

local pattern =
    Carg(1) / function(t)
        extra, tab, start = 0, t or 7, 1
    end
  * Cs((
      Cp() * patterns.tab / function(position)
          local current = (position - start + 1) + extra
          local spaces = tab-(current-1) % tab
          if spaces > 0 then
              extra = extra + spaces - 1
              return nspaces[spaces] -- rep(" ",spaces)
          else
              return ""
          end
      end
    + patterns.newline * Cp() / function(position)
          extra, start = 0, position
      end
    + patterns.anything
  )^1)

function strings.tabtospace(str,tab)
    return lpegmatch(pattern,str,1,tab or 7)
end

-- local t = {
--     "1234567123456712345671234567",
--     "\tb\tc",
--     "a\tb\tc",
--     "aa\tbb\tcc",
--     "aaa\tbbb\tccc",
--     "aaaa\tbbbb\tcccc",
--     "aaaaa\tbbbbb\tccccc",
--     "aaaaaa\tbbbbbb\tcccccc\n       aaaaaa\tbbbbbb\tcccccc",
--     "one\n	two\nxxx	three\nxx	four\nx	five\nsix",
-- }
-- for k=1,#t do
--     print(strings.tabtospace(t[k]))
-- end

function strings.striplong(str) -- strips all leading spaces
    str = gsub(str,"^%s*","")
    str = gsub(str,"[\n\r]+ *","\n")
    return str
end

-- local template = string.striplong([[
--   aaaa
--   bb
--   cccccc
-- ]])

function strings.nice(str)
    str = gsub(str,"[:%-+_]+"," ") -- maybe more
    return str
end

-- Work in progress. Interesting is that compared to the built-in this is faster in
-- luatex than in luajittex where we have a comparable speed. It only makes sense
-- to use the formatter when a (somewhat) complex format is used a lot. Each formatter
-- is a function so there is some overhead and not all formatted output is worth that
-- overhead. Keep in mind that there is an extra function call involved. In principle
-- we end up with a string concatination so one could inline such a sequence but often
-- at the cost of less readabinity. So, it's a sort of (visual) compromise. Of course
-- there is the benefit of more variants. (Concerning the speed: a simple format like
-- %05fpt is better off with format than with a formatter, but as soon as you put
-- something in front formatters become faster. Passing the pt as extra argument makes
-- formatters behave better. Of course this is rather implementation dependent. Also,
-- when a specific format is only used a few times the overhead in creating it is not
-- compensated by speed.)
--
-- More info can be found in cld-mkiv.pdf so here I stick to a simple list.
--
-- integer          %...i   number
-- integer          %...d   number
-- unsigned         %...u   number
-- character        %...c   number
-- hexadecimal      %...x   number
-- HEXADECIMAL      %...X   number
-- octal            %...o   number
-- string           %...s   string number
-- float            %...f   number
-- exponential      %...e   number
-- exponential      %...E   number
-- autofloat        %...g   number
-- autofloat        %...G   number
-- utf character    %...c   number
-- force tostring   %...S   any
-- force tostring   %Q      any
-- force tonumber   %N      number (strip leading zeros)
-- signed number    %I      number
-- rounded number   %r      number
-- 0xhexadecimal    %...h   character number
-- 0xHEXADECIMAL    %...H   character number
-- U+hexadecimal    %...u   character number
-- U+HEXADECIMAL    %...U   character number
-- points           %p      number (scaled points)
-- basepoints       %b      number (scaled points)
-- table concat     %...t   table
-- table concat     %{.}t   table
-- serialize        %...T   sequenced (no nested tables)
-- serialize        %{.}T   sequenced (no nested tables)
-- boolean (logic)  %l      boolean
-- BOOLEAN          %L      boolean
-- whitespace       %...w
-- automatic        %...a   'whatever' (string, table, ...)
-- automatic        %...A   "whatever" (string, table, ...)

local n = 0

-- we are somewhat sloppy in parsing prefixes as it's not that critical

-- hard to avoid but we can collect them in a private namespace if needed

-- inline the next two makes no sense as we only use this in logging

local sequenced = table.sequenced

function string.autodouble(s,sep)
    if s == nil then
        return '""'
    end
    local t = type(s)
    if t == "number" then
        return tostring(s) -- tostring not really needed
    end
    if t == "table" then
        return ('"' .. sequenced(s,sep or ",") .. '"')
    end
    return ('"' .. tostring(s) .. '"')
end

function string.autosingle(s,sep)
    if s == nil then
        return "''"
    end
    local t = type(s)
    if t == "number" then
        return tostring(s) -- tostring not really needed
    end
    if t == "table" then
        return ("'" .. sequenced(s,sep or ",") .. "'")
    end
    return ("'" .. tostring(s) .. "'")
end

local tracedchars  = { }
string.tracedchars = tracedchars
strings.tracers    = tracedchars

function string.tracedchar(b)
    -- todo: table
    if type(b) == "number" then
        return tracedchars[b] or (utfchar(b) .. " (U+" .. format('%05X',b) .. ")")
    else
        local c = utfbyte(b)
        return tracedchars[c] or (b .. " (U+" .. format('%05X',c) .. ")")
    end
end

function number.signed(i)
    if i > 0 then
        return "+",  i
    else
        return "-", -i
    end
end

local zero      = P("0")^1 / ""
local plus      = P("+")   / ""
local minus     = P("-")
local separator = S(".")
local digit     = R("09")
local trailing  = zero^1 * #S("eE")
local exponent  = (S("eE") * (plus + Cs((minus * zero^0 * P(-1))/"") + minus) * zero^0 * (P(-1) * Cc("0") + P(1)^1))
local pattern_a = Cs(minus^0 * digit^1 * (separator/"" * trailing + separator * (trailing + digit)^0) * exponent)
local pattern_b = Cs((exponent + P(1))^0)

function number.sparseexponent(f,n)
    if not n then
        n = f
        f = "%e"
    end
    local tn = type(n)
    if tn == "string" then -- cast to number
        local m = tonumber(n)
        if m then
            return lpegmatch((f == "%e" or f == "%E") and pattern_a or pattern_b,format(f,m))
        end
    elseif tn == "number" then
        return lpegmatch((f == "%e" or f == "%E") and pattern_a or pattern_b,format(f,n))
    end
    return tostring(n)
end

local preamble = [[
local type = type
local tostring = tostring
local tonumber = tonumber
local format = string.format
local concat = table.concat
local signed = number.signed
local points = number.points
local basepoints = number.basepoints
local utfchar = utf.char
local utfbyte = utf.byte
local lpegmatch = lpeg.match
local nspaces = string.nspaces
local tracedchar = string.tracedchar
local autosingle = string.autosingle
local autodouble = string.autodouble
local sequenced = table.sequenced
local formattednumber = number.formatted
local sparseexponent = number.sparseexponent
]]

local template = [[
%s
%s
return function(%s) return %s end
]]

local arguments = { "a1" } -- faster than previously used (select(n,...))

setmetatable(arguments, { __index =
    function(t,k)
        local v = t[k-1] .. ",a" .. k
        t[k] = v
        return v
    end
})

local prefix_any = C((S("+- .") + R("09"))^0)
local prefix_tab = P("{") * C((1-P("}"))^0) * P("}") + C((1-R("az","AZ","09","%%"))^0)

-- we've split all cases as then we can optimize them (let's omit the fuzzy u)

-- todo: replace outer formats in next by ..

local format_s = function(f)
    n = n + 1
    if f and f ~= "" then
        return format("format('%%%ss',a%s)",f,n)
    else -- best no tostring in order to stay compatible (.. does a selective tostring too)
        return format("(a%s or '')",n) -- goodie: nil check
    end
end

local format_S = function(f) -- can be optimized
    n = n + 1
    if f and f ~= "" then
        return format("format('%%%ss',tostring(a%s))",f,n)
    else
        return format("tostring(a%s)",n)
    end
end

local format_q = function()
    n = n + 1
    return format("(a%s and format('%%q',a%s) or '')",n,n) -- goodie: nil check (maybe separate lpeg, not faster)
end

local format_Q = function() -- can be optimized
    n = n + 1
    return format("format('%%q',tostring(a%s))",n)
end

local format_i = function(f)
    n = n + 1
    if f and f ~= "" then
        return format("format('%%%si',a%s)",f,n)
    else
        return format("format('%%i',a%s)",n)
    end
end

local format_d = format_i

local format_I = function(f)
    n = n + 1
    return format("format('%%s%%%si',signed(a%s))",f,n)
end

local format_f = function(f)
    n = n + 1
    return format("format('%%%sf',a%s)",f,n)
end

local format_g = function(f)
    n = n + 1
    return format("format('%%%sg',a%s)",f,n)
end

local format_G = function(f)
    n = n + 1
    return format("format('%%%sG',a%s)",f,n)
end

local format_e = function(f)
    n = n + 1
    return format("format('%%%se',a%s)",f,n)
end

local format_E = function(f)
    n = n + 1
    return format("format('%%%sE',a%s)",f,n)
end

local format_j = function(f)
    n = n + 1
    return format("sparseexponent('%%%se',a%s)",f,n)
end

local format_J = function(f)
    n = n + 1
    return format("sparseexponent('%%%sE',a%s)",f,n)
end

local format_x = function(f)
    n = n + 1
    return format("format('%%%sx',a%s)",f,n)
end

local format_X = function(f)
    n = n + 1
    return format("format('%%%sX',a%s)",f,n)
end

local format_o = function(f)
    n = n + 1
    return format("format('%%%so',a%s)",f,n)
end

local format_c = function()
    n = n + 1
    return format("utfchar(a%s)",n)
end

local format_C = function()
    n = n + 1
    return format("tracedchar(a%s)",n)
end

local format_r = function(f)
    n = n + 1
    return format("format('%%%s.0f',a%s)",f,n)
end

local format_h = function(f)
    n = n + 1
    if f == "-" then
        f = sub(f,2)
        return format("format('%%%sx',type(a%s) == 'number' and a%s or utfbyte(a%s))",f == "" and "05" or f,n,n,n)
    else
        return format("format('0x%%%sx',type(a%s) == 'number' and a%s or utfbyte(a%s))",f == "" and "05" or f,n,n,n)
    end
end

local format_H = function(f)
    n = n + 1
    if f == "-" then
        f = sub(f,2)
        return format("format('%%%sX',type(a%s) == 'number' and a%s or utfbyte(a%s))",f == "" and "05" or f,n,n,n)
    else
        return format("format('0x%%%sX',type(a%s) == 'number' and a%s or utfbyte(a%s))",f == "" and "05" or f,n,n,n)
    end
end

local format_u = function(f)
    n = n + 1
    if f == "-" then
        f = sub(f,2)
        return format("format('%%%sx',type(a%s) == 'number' and a%s or utfbyte(a%s))",f == "" and "05" or f,n,n,n)
    else
        return format("format('u+%%%sx',type(a%s) == 'number' and a%s or utfbyte(a%s))",f == "" and "05" or f,n,n,n)
    end
end

local format_U = function(f)
    n = n + 1
    if f == "-" then
        f = sub(f,2)
        return format("format('%%%sX',type(a%s) == 'number' and a%s or utfbyte(a%s))",f == "" and "05" or f,n,n,n)
    else
        return format("format('U+%%%sX',type(a%s) == 'number' and a%s or utfbyte(a%s))",f == "" and "05" or f,n,n,n)
    end
end

local format_p = function()
    n = n + 1
    return format("points(a%s)",n)
end

local format_b = function()
    n = n + 1
    return format("basepoints(a%s)",n)
end

local format_t = function(f)
    n = n + 1
    if f and f ~= "" then
        return format("concat(a%s,%q)",n,f)
    else
        return format("concat(a%s)",n)
    end
end

local format_T = function(f)
    n = n + 1
    if f and f ~= "" then
        return format("sequenced(a%s,%q)",n,f)
    else
        return format("sequenced(a%s)",n)
    end
end

local format_l = function()
    n = n + 1
    return format("(a%s and 'true' or 'false')",n)
end

local format_L = function()
    n = n + 1
    return format("(a%s and 'TRUE' or 'FALSE')",n)
end

local format_N = function() -- strips leading zeros
    n = n + 1
    return format("tostring(tonumber(a%s) or a%s)",n,n)
end

local format_a = function(f)
    n = n + 1
    if f and f ~= "" then
        return format("autosingle(a%s,%q)",n,f)
    else
        return format("autosingle(a%s)",n)
    end
end

local format_A = function(f)
    n = n + 1
    if f and f ~= "" then
        return format("autodouble(a%s,%q)",n,f)
    else
        return format("autodouble(a%s)",n)
    end
end

local format_w = function(f) -- handy when doing depth related indent
    n = n + 1
    f = tonumber(f)
    if f then -- not that useful
        return format("nspaces[%s+a%s]",f,n) -- no real need for tonumber
    else
        return format("nspaces[a%s]",n) -- no real need for tonumber
    end
end

local format_W = function(f) -- handy when doing depth related indent
    return format("nspaces[%s]",tonumber(f) or 0)
end

-- maybe to util-num

local digit  = patterns.digit
local period = patterns.period
local three  = digit * digit * digit

local splitter = Cs (
    (((1 - (three^1 * period))^1 + C(three)) * (Carg(1) * three)^1 + C((1-period)^1))
  * (P(1)/"" * Carg(2)) * C(2)
)

patterns.formattednumber = splitter

function number.formatted(n,sep1,sep2)
    local s = type(s) == "string" and n or format("%0.2f",n)
    if sep1 == true then
        return lpegmatch(splitter,s,1,".",",")
    elseif sep1 == "." then
        return lpegmatch(splitter,s,1,sep1,sep2 or ",")
    elseif sep1 == "," then
        return lpegmatch(splitter,s,1,sep1,sep2 or ".")
    else
        return lpegmatch(splitter,s,1,sep1 or ",",sep2 or ".")
    end
end

-- print(number.formatted(1))
-- print(number.formatted(12))
-- print(number.formatted(123))
-- print(number.formatted(1234))
-- print(number.formatted(12345))
-- print(number.formatted(123456))
-- print(number.formatted(1234567))
-- print(number.formatted(12345678))
-- print(number.formatted(12345678,true))
-- print(number.formatted(1234.56,"!","?"))

local format_m = function(f)
    n = n + 1
    if not f or f == "" then
        f = ","
    end
    return format([[formattednumber(a%s,%q,".")]],n,f)
end

local format_M = function(f)
    n = n + 1
    if not f or f == "" then
        f = "."
    end
    return format([[formattednumber(a%s,%q,",")]],n,f)
end

--

local format_z = function(f)
    n = n + (tonumber(f) or 1)
    return "''" -- okay, not that efficient to append '' but a special case anyway
end

--

local format_rest = function(s)
    return format("%q",s) -- catches " and \n and such
end

local format_extension = function(extensions,f,name)
    local extension = extensions[name] or "tostring(%s)"
    local f = tonumber(f) or 1
    if f == 0 then
        return extension
    elseif f == 1 then
        n = n + 1
        local a = "a" .. n
        return format(extension,a,a) -- maybe more times?
    elseif f < 0 then
        local a = "a" .. (n + f + 1)
        return format(extension,a,a)
    else
        local t = { }
        for i=1,f do
            n = n + 1
            t[#t+1] = "a" .. n
        end
        return format(extension,unpack(t))
    end
end

-- aA b cC d eE f gG hH iI jJ lL mM N o p qQ r sS tT uU wW xX z

local builder = Cs { "start",
    start = (
        (
            P("%") / ""
          * (
                V("!") -- new
              + V("s") + V("q")
              + V("i") + V("d")
              + V("f") + V("g") + V("G") + V("e") + V("E")
              + V("x") + V("X") + V("o")
              --
              + V("c")
              + V("C")
              + V("S") -- new
              + V("Q") -- new
              + V("N") -- new
              --
              + V("r")
              + V("h") + V("H") + V("u") + V("U")
              + V("p") + V("b")
              + V("t") + V("T")
              + V("l") + V("L")
              + V("I")
              + V("w") -- new
              + V("W") -- new
              + V("a") -- new
              + V("A") -- new
              + V("j") + V("J") -- stripped e E
              + V("m") + V("M") -- new
              + V("z") -- new
              --
              + V("*") -- ignores probably messed up %
            )
          + V("*")
        )
     * (P(-1) + Carg(1))
    )^0,
    --
    ["s"] = (prefix_any * P("s")) / format_s, -- %s => regular %s (string)
    ["q"] = (prefix_any * P("q")) / format_q, -- %q => regular %q (quoted string)
    ["i"] = (prefix_any * P("i")) / format_i, -- %i => regular %i (integer)
    ["d"] = (prefix_any * P("d")) / format_d, -- %d => regular %d (integer)
    ["f"] = (prefix_any * P("f")) / format_f, -- %f => regular %f (float)
    ["g"] = (prefix_any * P("g")) / format_g, -- %g => regular %g (float)
    ["G"] = (prefix_any * P("G")) / format_G, -- %G => regular %G (float)
    ["e"] = (prefix_any * P("e")) / format_e, -- %e => regular %e (float)
    ["E"] = (prefix_any * P("E")) / format_E, -- %E => regular %E (float)
    ["x"] = (prefix_any * P("x")) / format_x, -- %x => regular %x (hexadecimal)
    ["X"] = (prefix_any * P("X")) / format_X, -- %X => regular %X (HEXADECIMAL)
    ["o"] = (prefix_any * P("o")) / format_o, -- %o => regular %o (octal)
    --
    ["S"] = (prefix_any * P("S")) / format_S, -- %S => %s (tostring)
    ["Q"] = (prefix_any * P("Q")) / format_S, -- %Q => %q (tostring)
    ["N"] = (prefix_any * P("N")) / format_N, -- %N => tonumber (strips leading zeros)
    ["c"] = (prefix_any * P("c")) / format_c, -- %c => utf character (extension to regular)
    ["C"] = (prefix_any * P("C")) / format_C, -- %c => U+.... utf character
    --
    ["r"] = (prefix_any * P("r")) / format_r, -- %r => round
    ["h"] = (prefix_any * P("h")) / format_h, -- %h => 0x0a1b2 (when - no 0x) was v
    ["H"] = (prefix_any * P("H")) / format_H, -- %H => 0x0A1B2 (when - no 0x) was V
    ["u"] = (prefix_any * P("u")) / format_u, -- %u => u+0a1b2 (when - no u+)
    ["U"] = (prefix_any * P("U")) / format_U, -- %U => U+0A1B2 (when - no U+)
    ["p"] = (prefix_any * P("p")) / format_p, -- %p => 12.345pt / maybe: P (and more units)
    ["b"] = (prefix_any * P("b")) / format_b, -- %b => 12.342bp / maybe: B (and more units)
    ["t"] = (prefix_tab * P("t")) / format_t, -- %t => concat
    ["T"] = (prefix_tab * P("T")) / format_T, -- %t => sequenced
    ["l"] = (prefix_any * P("l")) / format_l, -- %l => boolean
    ["L"] = (prefix_any * P("L")) / format_L, -- %L => BOOLEAN
    ["I"] = (prefix_any * P("I")) / format_I, -- %I => signed integer
    --
    ["w"] = (prefix_any * P("w")) / format_w, -- %w => n spaces (optional prefix is added)
    ["W"] = (prefix_any * P("W")) / format_W, -- %W => mandate prefix, no specifier
    --
    ["j"] = (prefix_any * P("j")) / format_j, -- %j => %e (float) stripped exponent (irrational)
    ["J"] = (prefix_any * P("J")) / format_J, -- %J => %E (float) stripped exponent (irrational)
    --
    ["m"] = (prefix_tab * P("m")) / format_m, -- %m => xxx.xxx.xxx,xx (optional prefix instead of .)
    ["M"] = (prefix_tab * P("M")) / format_M, -- %M => xxx,xxx,xxx.xx (optional prefix instead of ,)
    --
    ["z"] = (prefix_any * P("z")) / format_z, -- %M => xxx,xxx,xxx.xx (optional prefix instead of ,)
    --
    ["a"] = (prefix_any * P("a")) / format_a, -- %a => '...' (forces tostring)
    ["A"] = (prefix_any * P("A")) / format_A, -- %A => "..." (forces tostring)
    --
    ["*"] = Cs(((1-P("%"))^1 + P("%%")/"%%")^1) / format_rest, -- rest (including %%)
    --
    ["!"] = Carg(2) * prefix_any * P("!") * C((1-P("!"))^1) * P("!") / format_extension,
}

-- we can be clever and only alias what is needed

local direct = Cs (
        P("%")/""
      * Cc([[local format = string.format return function(str) return format("%]])
      * (S("+- .") + R("09"))^0
      * S("sqidfgGeExXo")
      * Cc([[",str) end]])
      * P(-1)
    )

local function make(t,str)
    local f
    local p
    local p = lpegmatch(direct,str)
    if p then
        f = loadstripped(p)()
    else
        n = 0
        p = lpegmatch(builder,str,1,"..",t._extensions_) -- after this we know n
        if n > 0 then
            p = format(template,preamble,t._preamble_,arguments[n],p)
--         print("builder>",p)
            f = loadstripped(p)()
        else
            f = function() return str end
        end
    end
    t[str] = f
    return f
end

-- -- collect periodically
--
-- local threshold = 1000 -- max nof cached formats
--
-- local function make(t,str)
--     local f = rawget(t,str)
--     if f then
--         return f
--     end
--     local parent = t._t_
--     if parent._n_ > threshold then
--         local m = { _t_ = parent }
--         getmetatable(parent).__index = m
--         setmetatable(m, { __index = make })
--     else
--         parent._n_ = parent._n_ + 1
--     end
--     local f
--     local p = lpegmatch(direct,str)
--     if p then
--         f = loadstripped(p)()
--     else
--         n = 0
--         p = lpegmatch(builder,str,1,"..",parent._extensions_) -- after this we know n
--         if n > 0 then
--             p = format(template,preamble,parent._preamble_,arguments[n],p)
--          -- print("builder>",p)
--             f = loadstripped(p)()
--         else
--             f = function() return str end
--         end
--     end
--     t[str] = f
--     return f
-- end

local function use(t,fmt,...)
    return t[fmt](...)
end

strings.formatters = { }

-- we cannot make these tables weak, unless we start using an indirect
-- table (metatable) in which case we could better keep a count and
-- clear that table when a threshold is reached

function strings.formatters.new()
    local t = { _extensions_ = { }, _preamble_ = "", _type_ = "formatter" }
    setmetatable(t, { __index = make, __call = use })
    return t
end

-- function strings.formatters.new()
--     local t = { _extensions_ = { }, _preamble_ = "", _type_ = "formatter", _n_ = 0 }
--     local m = { _t_ = t }
--     setmetatable(t, { __index = m, __call = use })
--     setmetatable(m, { __index = make })
--     return t
-- end

local formatters   = strings.formatters.new() -- the default instance

string.formatters  = formatters -- in the main string namespace
string.formatter   = function(str,...) return formatters[str](...) end -- sometimes nicer name

local function add(t,name,template,preamble)
    if type(t) == "table" and t._type_ == "formatter" then
        t._extensions_[name] = template or "%s"
        if preamble then
            t._preamble_ = preamble .. "\n" .. t._preamble_ -- so no overload !
        end
    end
end

strings.formatters.add = add

-- registered in the default instance (should we fall back on this one?)

patterns.xmlescape = Cs((P("<")/"&lt;" + P(">")/"&gt;" + P("&")/"&amp;" + P('"')/"&quot;" + P(1))^0)
patterns.texescape = Cs((C(S("#$%\\{}"))/"\\%1" + P(1))^0)
patterns.luaescape = Cs(((1-S('"\n'))^1 + P('"')/'\\"' + P('\n')/'\\n"')^0) -- maybe also \0
patterns.luaquoted = Cs(Cc('"') * ((1-S('"\n'))^1 + P('"')/'\\"' + P('\n')/'\\n"')^0 * Cc('"'))

-- escaping by lpeg is faster for strings without quotes, slower on a string with quotes, but
-- faster again when other q-escapables are found (the ones we don't need to escape)

add(formatters,"xml", [[lpegmatch(xmlescape,%s)]],[[local xmlescape = lpeg.patterns.xmlescape]])
add(formatters,"tex", [[lpegmatch(texescape,%s)]],[[local texescape = lpeg.patterns.texescape]])
add(formatters,"lua", [[lpegmatch(luaescape,%s)]],[[local luaescape = lpeg.patterns.luaescape]])

-- -- yes or no:
--
-- local function make(t,str)
--     local f
--     local p = lpegmatch(direct,str)
--     if p then
--         f = loadstripped(p)()
--     else
--         n = 0
--         p = lpegmatch(builder,str,1,",") -- after this we know n
--         if n > 0 then
--             p = format(template,template_shortcuts,arguments[n],p)
--             f = loadstripped(p)()
--         else
--             f = function() return str end
--         end
--     end
--     t[str] = f
--     return f
-- end
--
-- local formatteds  = string.formatteds or { }
-- string.formatteds = formatteds
--
-- setmetatable(formatteds, { __index = make, __call = use })