splitWithNesting, Sequence<String>.flatten(), path fix on win

src/main/kotlin/blitz/str/SplitWithNesting.kt

@@ -0,0 +1,33 @@
+package blitz.str
+
+fun String.splitWithNesting(
+    delim: Char,
+    nestUp: Char,
+    nestDown: Char,
+    dest: MutableList<String> = mutableListOf()
+): MutableList<String> {
+    val last = StringBuilder()
+    val iter = iterator()
+    var nesting = 0
+    while (iter.hasNext()) {
+        val c = iter.next()
+        if (nesting == 0 && c == delim) {
+            dest.add(last.toString())
+            last.clear()
+        } else if (c == nestUp) {
+            nesting ++
+            last.append(c)
+        } else if (c == nestDown) {
+            if (nesting == 0)
+                throw Exception("Unmatched $nestDown")
+            nesting --
+            last.append(c)
+        } else {
+            last.append(c)
+        }
+    }
+    dest.add(last.toString())
+    if (nesting != 0)
+        throw Exception("Unmatched $nestUp")
+    return dest
+}