From 6f26d36bae242d3e38a678a005144998b81112fb Mon Sep 17 00:00:00 2001
From: Lucien Cartier-Tilet <lucien@phundrak.com>
Date: Wed, 29 Jan 2020 21:49:21 +0100
Subject: [PATCH] Simplified tree-to-dot

---
 funcs.el | 77 +++++++++++++++++++++++++-------------------------------
 1 file changed, 34 insertions(+), 43 deletions(-)

diff --git a/funcs.el b/funcs.el
index 9e041bf..a5bd4fe 100644
--- a/funcs.el
+++ b/funcs.el
@@ -15,52 +15,43 @@
 (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
-          "\"];"))
+  (format "%d[label=\"%s\"];\n" node-generation
+          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.
+(defun conlanging/tree-to-dot (tree &optional current-generation previous-generation)
+  "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"
+- `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{graph[dpi=300];node[shape=plaintext];graph[bgcolor=\"transparent\"];"
-     (conlanging//declare-node (car tree) 0)
-     (conlanging//tree-to-dot-helper (cdr tree) 1 0)
-     "}")))
+   ((null previous-generation) ;; first call
+    (concat "graph{graph[dpi=300];node[shape=plaintext];graph[bgcolor=\"transparent\"];\n"
+            (conlanging//declare-node (car tree) 0)
+            (conlanging/tree-to-dot (cdr tree) 1 0)
+            "}"))
+   ((null tree) "") ;; last call in this branch
+   ((atom (car tree)) ;; '("text" () () ()) manage the label
+    (concat (conlanging//declare-node (car tree)
+                                      current-generation)
+            ;; make link
+            (concat (number-to-string previous-generation) " -- "
+                    (number-to-string current-generation) ";\n")
+            (conlanging/tree-to-dot (cdr tree)
+                                    (+ 1
+                                       (* 10 current-generation))
+                                    current-generation)))
+   ((listp (car tree)) ;; '(() () ()) manage the branches
+    (concat (conlanging/tree-to-dot (car tree) ;; child of current node
+                                    current-generation
+                                    previous-generation)
+            (conlanging/tree-to-dot (cdr tree)
+                                    (+ 1 current-generation)
+                                    previous-generation)))))
 
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