julia.withPackages: init on supported Julias (1.6, 1.8, 1.9)

Be able to build arbitrary Julia environments in Nixpkgs, in the same style as python.withPackages.

pkgs/development/julia-modules/python/dag.py

@@ -0,0 +1,59 @@
+
+# This file based on a ChatGPT reponse for the following prompt:
+# "can you write code in python to build up a DAG representing
+# a dependency tree, and then a function that can return all the
+# dependencies of a given node?"
+
+class Node:
+    def __init__(self, name):
+        self.name = name
+        self.dependencies = set()
+
+
+class DAG:
+    def __init__(self):
+        self.nodes = {}
+
+    def add_node(self, node_name, dependencies=None):
+        if node_name in self.nodes:
+            raise ValueError(f"Node '{node_name}' already exists in the graph.")
+
+        node = Node(node_name)
+        if dependencies:
+            node.dependencies.update(dependencies)
+
+        self.nodes[node_name] = node
+
+    def add_dependency(self, node_name, dependency_name):
+        if node_name not in self.nodes:
+            raise ValueError(f"Node '{node_name}' does not exist in the graph.")
+
+        if dependency_name not in self.nodes:
+            raise ValueError(f"Dependency '{dependency_name}' does not exist in the graph.")
+
+        self.nodes[node_name].dependencies.add(dependency_name)
+
+    def get_dependencies(self, node_name):
+        if node_name not in self.nodes:
+            raise ValueError(f"Node '{node_name}' does not exist in the graph.")
+
+        node = self.nodes[node_name]
+        dependencies = set()
+
+        def traverse_dependencies(current_node):
+            for dependency in current_node.dependencies:
+                dependencies.add(dependency)
+                if dependency in self.nodes:
+                  traverse_dependencies(self.nodes[dependency])
+
+        traverse_dependencies(node)
+        return dependencies
+
+    def has_node(self, node_name):
+        return node_name in self.nodes
+
+    def __str__(self):
+        graph_str = ""
+        for node_name, node in self.nodes.items():
+            graph_str += f"{node_name} -> {', '.join(node.dependencies)}\n"
+        return graph_str