bugfix in buffer object. Didn't increase the refcount when slicing

src/lib/builtins/start.noja

@@ -1 +1,88 @@
-name = "Francesco";
+
+fun abs(n: Numeric) {
+	if n < 0:
+		return -n;
+	return n;
+}
+
+fun min(x, y) {
+    if x < y:
+        return x;
+    return y;
+}
+
+fun max(x, y) {
+    if x > y:
+        return x;
+    return y;
+}
+
+Func  = type(abs);
+NFunc = type(print);
+Numeric = int | float;
+Callable = Func | NFunc;
+Collection = List | Map;
+
+# Stringify a number between 0 and 9.
+fun stringFromDigit(digit: int) {
+	assert(digit >= 0 and digit <= 9);
+	return string.chr(string.ord("0") + digit);
+}
+
+# Stringify an unsigned integer
+fun stringFromInteger(n: int) {
+
+	# This function returns the magnitude of the
+	# argument and the power of 10 with the same
+	# magnitude.
+	fun getIntegerMagnitude(n: int) {
+		assert(n >= 0);
+		magn = 0;
+		powr = 1;
+		# Basically grow the power until it's
+		# bigger than the input.
+		while n >= powr * 10: {
+			powr = 10 * powr;
+			magn = 1 + magn;
+		}
+		return magn, powr;
+	}
+
+	negative = (n < 0);
+	
+	# Get the power of 10 with the
+	# magnitude of the input.
+	_, power = getIntegerMagnitude(n);
+
+	temp = abs(n); # Temporary copy of the input
+	text = ""; # The output we're about to compute
+
+	while power >= 1: {
+		# Pop the leftmost digit from [temp].
+		digit = temp / power; # Get the leftmost digit
+		temp  = temp % power; # Remove it
+
+		# Add the digit to the output.
+		text = string.cat(text, stringFromDigit(digit));
+
+		# Prep for the next iteration.
+		power = power / 10;
+	}
+
+	if negative:
+		text = string.cat("-", text);
+	return text;
+}
+
+fun floatFromInteger(n: int)
+	return 1.0 * n;
+
+fun integerFromDigit(char: String) {
+    res = ord(char) - ord('0');
+    if res < 0 or res > 9:
+    	error("String isn't a digit");
+    return res;
+}
+
+fun append(array: List, item)
+	array[count(array)] = item;