From 74411f32c3dbeefbc6497e94abf8dfa2f0fd61bf Mon Sep 17 00:00:00 2001
From: Justin Lin <justin.sdk@gmail.com>
Date: Sun, 8 May 2022 10:19:09 +0800
Subject: [PATCH] refactor

---
 src/turtle/_impl/_lsystem2_impl.scad |  4 +---
 src/turtle/_impl/_lsystem3_impl.scad |  4 +---
 src/turtle/_impl/_lsystem_comm.scad  | 14 +++++++++-----
 3 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/src/turtle/_impl/_lsystem2_impl.scad b/src/turtle/_impl/_lsystem2_impl.scad
index 7706e435..7c18d1a1 100644
--- a/src/turtle/_impl/_lsystem2_impl.scad
+++ b/src/turtle/_impl/_lsystem2_impl.scad
@@ -3,9 +3,7 @@ use <../turtle2d.scad>;
 
 function _lsystem2_join(str_lt) = _join(str_lt);
 
-function _lsystem2_derive(axiom, rules, n, rule_prs) =
-    is_undef(rule_prs) ? _derive(axiom, rules, n) :
-                         _derive_p(axiom, rules, rule_prs, n);
+function _lsystem2_derive(axiom, rules, n, rule_prs) = _derive(axiom, rules, n, rule_prs);
 
 function _next_stack(t, code, stack) = 
     code == "[" ? [t, each stack] :
diff --git a/src/turtle/_impl/_lsystem3_impl.scad b/src/turtle/_impl/_lsystem3_impl.scad
index 5c021650..ec0496b1 100644
--- a/src/turtle/_impl/_lsystem3_impl.scad
+++ b/src/turtle/_impl/_lsystem3_impl.scad
@@ -3,9 +3,7 @@ use <../turtle3d.scad>;
 
 function _lsystem3_join(str_lt) = _join(str_lt);
 
-function _lsystem3_derive(axiom, rules, n, rule_prs) =
-    is_undef(rule_prs) ? _derive(axiom, rules, n) :
-                         _derive_p(axiom, rules, rule_prs, n);
+function _lsystem3_derive(axiom, rules, n, rule_prs) = _derive(axiom, rules, n, rule_prs);
 
 function _next_stack(t, code, stack) = 
     code == "[" ? [t, each stack] :
diff --git a/src/turtle/_impl/_lsystem_comm.scad b/src/turtle/_impl/_lsystem_comm.scad
index c2a166ca..f605d3da 100644
--- a/src/turtle/_impl/_lsystem_comm.scad
+++ b/src/turtle/_impl/_lsystem_comm.scad
@@ -21,14 +21,18 @@ function _derive1_p(base, rules, rules_pr) =
         v == [] ? c : c_or_v(c, v, rules, rules_pr, len(v))
     ]);
 
-function _derive_p(base, rules, rules_pr, n, i = 0) =
-    i == n ? base : _derive_p(_derive1_p(base, rules, rules_pr), rules, rules_pr, n, i + 1);
-
 function _derive1(base, rules) = _join([
     for(c = base) 
     let(v = _assoc_lookup(rules, c))
     is_undef(v) ? c : v
 ]);
 
-function _derive(base, rules, n, i = 0) =
-    i == n ? base : _derive(_derive1(base, rules), rules, n, i + 1);
\ No newline at end of file
+function _derive(base, rules, n, rule_prs) =
+    let(
+        derive = is_undef(rule_prs) ? function(base) _derive1(base, rules) : function(base) _derive1_p(base, rules, rules_pr),
+        bs = [
+            for(i = 0, b = derive(base); i < n; i = i + 1, b = i != n ? derive(b) : undef)
+            b
+        ]
+    )
+    bs[len(bs) - 1];
\ No newline at end of file