Ad function description

day-18/day-18.py

@@ -3,6 +3,15 @@ from pathlib import Path
 
 
 def parse(line):
+    """This function parses an input line to nested tuples of length 2. It works by stripping the
+    outermost bracket-pair from the string and counting the 'depth' of the current brackets. After
+    we got back to the initial level 0 the next comma marks the index where the left and right part
+    are seperated. Those will be parsed by a recursive parse call each. If there is no comma on a
+    line, we are on the deepest level of this branch and return the value as integer. Else the left
+    and right return value will be returned in a tuple. The result will bea binary tree of the
+    snailfish number.
+    Alternatives for parsing would be eval() - which can be unsafe and is slow - or json.parse().
+    """
     if ',' not in line:
         return int(line)
     line = line[1:-1]