fix alg2

alg2.lua

@@ -1,4 +1,26 @@
-local function stringToTable(str)
+-- based on https://www.lua.org/pil/20.4.html
+local function code(s)
+    -- mask all escaped characters
+    return s:gsub("\\(.)", function (c)
+        return string.format("\\%03d", string.byte(c))
+    end):gsub("([\"'])(.-)%1", function (_, match) -- detect all strings
+        return "'" .. match:gsub("([,;{}%[%]=])", function (c)
+            return string.format("\\%03d", string.byte(c))
+        end) .. "'"
+    end)
+end
+
+local function decode(s)
+    return s:gsub("\\(%d%d%d)", function (d)
+        return string.char(d)
+    end)
+end
+
+
+local function codedStringToTable(str)
+    -- special case: hadle empty tables (our parser would break here)
+    if str:find("^{%s*}$") then return {} end
+
     local function parseValue(s)
         s = s:match("^%s*(.-)%s*$") -- trim whitespace
 
@@ -11,20 +33,41 @@ local function stringToTable(str)
         elseif tonumber(s) then
             return tonumber(s)
         elseif s:match("^\".*\"$") or s:match("^'.*'$") then
-            return s:sub(2, -2):gsub("\\(.)", "%1") -- handle escape sequences
+            return decode(s:sub(2, -2))
-        elseif s:match("^%b{}$") then
+        elseif s:match("^{.*}$") then
-            return stringToTable(s)
+            return codedStringToTable(s)
         else
             error("Unrecognized value: " .. s)
         end
     end
 
+    local function parseKey(s)
+        s = s:match("^%s*(.-)%s*$") -- trim whitespace
+        if s:match("^%[(.*)%]$") then
+            return parseValue(s:match("^%[(.*)%]$"))
+        elseif s:find("^[%a_][%a%d_]*$") then -- make sure the string is a valid lua identifier
+            return s
+        else
+            error("Unrecognized key: " .. s)
+        end
+    end
+
     local tbl = {}
     local key, value
+    local next_key = 1
     local inKey = true
     local depth = 0
     local buffer = ""
 
+    local function getNextKey()
+        while tbl[next_key] ~= nil do
+            next_key = next_key + 1
+        end
+        key = next_key
+        next_key = next_key + 1
+        return key
+    end
+
     for i = 1, #str do
         local char = str:sub(i, i)
         
@@ -33,44 +76,44 @@ local function stringToTable(str)
                 buffer = buffer .. char
             end
             depth = depth + 1
-
         elseif char == '}' then
             depth = depth - 1
             if depth > 0 then
                 buffer = buffer .. char
-            elseif depth == 0 and buffer ~= "" then
+            elseif depth == 0 and not buffer:find("^%s*$") then
-                value = buffer
-                buffer = ""
-            end
-
-        elseif char == ',' and depth == 1 then
-            if inKey then
-                key = parseValue(buffer)
-            else
                 value = parseValue(buffer)
-                tbl[key] = value
+                buffer = ""
+            end
+        elseif (char == ',' or char == ";") and depth == 1 then
+            value = parseValue(buffer)
+            if key == nil then
+                key = getNextKey()
             end
-            buffer = ""
-            inKey = not inKey
 
+            tbl[key] = value
+            key, value = nil, nil
+            buffer = ""
         elseif char == '=' and depth == 1 then
-            key = parseValue(buffer)
+            key = parseKey(buffer)
             buffer = ""
-            inKey = false
-
         else
             buffer = buffer .. char
         end
+    end
 
-        if depth == 1 and i == #str and buffer ~= "" then
+    if key == nil then
-            value = parseValue(buffer)
+        key = getNextKey()
+    end
     tbl[key] = value
-        end
-    end
 
     return tbl
 end
 
+local function stringToTable(str)
+    str = code(str)
+    return codedStringToTable(str)
+end
+
 function test_string_to_table.s2t2(str)
     return stringToTable(str)
 end

init.lua

@@ -22,7 +22,7 @@ local tests = {
     '{[-42.42e42] = 42.42E-42}',
     '{1, 2, 3, }',
     -- invalid tables, the code should return an error
-    -- --[[
+    --[[
     "{a = 1",
     "{'unclosed string\\'}",
     "{invalid key = 3}",
@@ -48,6 +48,6 @@ local function test(alg)
 end
 
 -- test("s2t1")
--- test("s2t2")
+test("s2t2")
 -- test("s2t3")
 test("s2ttour")