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POHow to split two nested lists and combine the parts to create two new nested lists
 

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  1. POHow to split two nested lists and combine the parts to create two new nested lists
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    <p>I'm trying to code a simple genetic programming utility in python. But right now I'm stuck at the crossover/mate function for my trees. The trees are built by nested lists and look something like this:</p> <pre><code># f = internal node (a function), c = leaf node (a constant) tree1 = [f, [f, [f, c, c], [f, c, c]], [f, [f, c, c], [f, c, c]]] tree2 = [f, [f, [f, c, c], c], [f, [f, c, c], c]] </code></pre> <p>I want to randomly select a point in each tree to split at and then I want one part from each tree to be combined into a new tree. There is also a max depth that shouldn't be exceeded so the selects can't really take place anywhere in the tree as it might create a too large tree. Below is an example on how it should work:</p> <pre><code># f:n, where n is the number of arguments the function take # + split here tree1 = [f:2, [f:3, a, a, a], a] # + split here tree2 = [f:2, [f:2, a, a], [f:1, a] tree_child1 = [f:2, [f:1, a], a] tree_child2 = [f:2, [f:2, a, a], [f:3, a, a, a]] </code></pre> <p>I have no idea (at the moment) on how to solve this. Any tips or solutions are more than welcome!</p> <p>(Added my parse function as it might help someone to understand the structure better.)</p> <pre><code># My recursive code to parse the tree. def parse(self, node=None): if not node: node = self.root if isinstance(node, list): function = node[0] res = [] for child in node[1:function.arity+1]: res.append(self.parse(child)) value = function.parse(*res) # function else: value = node.parse() # constant return value </code></pre>
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    1. COI would suggest to make simple datastructure of tree using node objects instead of using nested list, that will make it more readable and you will be able to put more book keeping data and methods into each node.
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      1. USAnurag Uniyal
 

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