added function to create graphviz trees

funcs.el

@@ -9,6 +9,59 @@
 ;;
 ;;; License: GPLv3
 
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+                                        ;                 Tree                ;
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+(defun conlanging//declare-node (node-text node-generation)
+  "Declares a node in the graphviz source code. The node’s identifier will be
+~node-generation~, and it will bear the label ~node-text~."
+  (concat (number-to-string node-generation)
+          "[label=\""
+          node-text
+          "\"];"))
+
+(defun conlanging//make-link (previous-node current-node)
+  "This creates a link in the graphviz source code between the two nodes
+bearing ~previous-node~ and ~current-node~ respectively as their node
+identifier."
+  (concat (number-to-string previous-node) " -- "
+          (number-to-string current-node) ";"))
+
+(defun conlanging//tree-to-dot-helper (tree current-generation previous-generation)
+  "Helper to ~tree-to-dot~ that translates an Elisp tree with any number of
+children per node to a corresponding graphviz file that can be executed from
+dot.
+Arguments:
+- tree :: tree-to-convert
+- current-generation :: Generation number, incremented when changing from a node
+     to another node from the same generation, multiplied by 10 when going from
+     a node to one of its children.
+- previous-generation :: generation number from previous named node"
+  (cond
+   ((null tree) "")
+   ((atom (car tree)) ;; '("text" () () ())
+    (concat (conlanging//declare-node (car tree) current-generation)
+            (conlanging//make-link previous-generation current-generation)
+            (conlanging//tree-to-dot-helper (cdr tree)
+                                (+ 1 (* 10 current-generation))
+                                current-generation)))
+   ((listp (car tree)) ;; '(() () ())
+    (concat (conlanging//tree-to-dot-helper (car tree) ;; child of current node
+                                current-generation
+                                previous-generation)
+            (conlanging//tree-to-dot-helper (cdr tree)
+                                (+ 1 current-generation)
+                                previous-generation)))))
+
+(defun conlanging/tree-to-dot (tree)
+  "Returns a graphviz’s dot compatible string representing an Elisp tree"
+  (if (null tree) ""
+    (concat
+     "graph{node[shape=plaintext];graph[bgcolor=\"transparent\"];"
+     (conlanging//declare-node (car tree) 0)
+     (conlanging//tree-to-dot-helper (cdr tree) 1 0)
+     "}")))
+
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