added stdlib.lua + lua errors handling update

res/scripts/stdlib.lua

@@ -0,0 +1,51 @@
+-- kit of standard functions
+
+-- Check if given table is an array
+function is_array(x)
+    if #t > 0 then
+        return true
+    end
+    for k, v in pairs(x) do
+        return false
+    end
+    return true
+end
+
+local __cached_scripts = {}
+local __cached_results = {}
+
+-- Get entry-point and filename from `entry-point:filename` path 
+function parse_path(path)
+    local index = string.find(path, ':')
+    if index == nil then
+        error("invalid path syntax (':' missing)")
+    end
+    return string.sub(path, 1, index-1), string.sub(path, index+1, -1)
+end
+
+-- Load script with caching
+--
+-- path - script path `contentpack:filename`. 
+--     Example `base:scripts/tests.lua`
+--
+-- nocache - ignore cached script, load anyway
+function load_script(path, nocache)
+    local packname, filename = parse_path(path)
+    local packpath = pack.get_folder(packname)
+    local fullpath = packpath..filename
+
+    -- __cached_scripts used in condition because cached result may be nil
+    if not nocache and __cached_scripts[fullpath] ~= nil then
+        return __cached_results[fullpath]
+    end
+    local script = loadfile(fullpath)
+    if script == nil then
+        error("script '"..filename.."' not found in '"..packname.."'")
+    end
+    local result = script()
+    if not nocache then
+        __cached_scripts[fullpath] = script
+        __cached_results[fullpath] = result
+    end
+    return result
+end