Start adding code generation

src/graph/properties.jl

@@ -27,3 +27,18 @@ function get_exit_node(graph::DAG)
     end
     @assert false "The given graph has no exit node! It is either empty or not acyclic!"
 end
+
+"""
+    get_entry_nodes(graph::DAG)
+
+Return a vector of the graph's entry nodes.
+"""
+function get_entry_nodes(graph::DAG)
+    result = Vector{Node}()
+    for node in graph.nodes
+        if (is_entry_node(node))
+            push!(result, node)
+        end
+    end
+    return result
+end