adding missing char.lua

Author: hellpanderrr

wiktionary_pron/lua_modules/string/char.lua

@@ -0,0 +1,50 @@
+local char = string.char
+
+local concat = table.concat
+local tonumber = tonumber
+
+local function err(cp)
+    error("Codepoint " .. cp .. " is out of range: codepoints must be between 0x0 and 0x10FFFF.", 2)
+end
+
+local function utf8_char(cp)
+    cp = tonumber(cp)
+    if cp < 0 then
+        err("-0x" .. ("%X"):format(-cp + 1))
+    elseif cp < 0x80 then
+        return char(cp)
+    elseif cp < 0x800 then
+        return char(
+                0xC0 + cp / 0x40,
+                0x80 + cp % 0x40
+        )
+    elseif cp < 0x10000 then
+        if cp >= 0xD800 and cp < 0xE000 then
+            return "?" -- mw.ustring.char returns "?" for surrogates.
+        end
+        return char(
+                0xE0 + cp / 0x1000,
+                0x80 + cp / 0x40 % 0x40,
+                0x80 + cp % 0x40
+        )
+    elseif cp < 0x110000 then
+        return char(
+                0xF0 + cp / 0x40000,
+                0x80 + cp / 0x1000 % 0x40,
+                0x80 + cp / 0x40 % 0x40,
+                0x80 + cp % 0x40
+        )
+    end
+    err("0x" .. ("%X"):format(cp))
+end
+
+return function(cp, ...)
+    if ... == nil then
+        return utf8_char(cp)
+    end
+    local ret = { cp, ... }
+    for i = 1, #ret do
+        ret[i] = utf8_char(ret[i])
+    end
+    return concat(ret)
+end