add binary_search

src/experimental/note.md

@@ -15,7 +15,7 @@ new:
 - t3d - roll/pitch/forward
 - polyline_join: doc multi-childs
 
-- util/count
+- util/count、binary_search
 - lemniscate_curve?
 - perlin_sphere?
 

src/util/_impl/_binary_search_impl.scad

@@ -0,0 +1,6 @@
+function _binary_search_impl(sorted, cmp, low, upper) =
+    low > upper ? -1 :
+    let(mid = floor((low + upper) / 2), compared = cmp(sorted[mid]))
+    compared == 0 ? mid :
+    let(lu = compared < 0 ? [mid + 1, upper] : [low, mid - 1])
+    _binary_search_impl(sorted, cmp, lu[0], lu[1]);

src/util/binary_search.scad

@@ -0,0 +1,19 @@
+/**
+* bsearch.scad
+*
+* @copyright Justin Lin, 2020
+* @license https://opensource.org/licenses/lgpl-3.0.html
+*
+* @see https://openhome.cc/eGossip/OpenSCAD/lib3x-bsearch.html
+*
+**/
+
+use <_impl/_binary_search_impl.scad>;
+
+function binary_search(sorted, target) = 
+    _binary_search_impl(
+        sorted, 
+        is_function(target) ? target : function(elem) elem == target ? 0 : elem > target ? 1 : -1, 
+        0, 
+        len(sorted) - 1
+    );

test/test_all.scad

@@ -67,10 +67,8 @@ include <util/test_sub_str.scad>;
 include <util/test_split_str.scad>;
 include <util/test_parse_number.scad>;
 include <util/test_slice.scad>;
-include <util/test_sorted.scad>;
 include <util/test_reverse.scad>;
 include <util/test_fibseq.scad>;
-include <util/test_bsearch.scad>;
 include <util/test_choose.scad>;
 include <util/test_dedup.scad>;
 include <util/test_zip.scad>;
@@ -82,7 +80,8 @@ include <util/test_spherical_coordinate.scad>;
 include <util/test_count.scad>;
 include <util/set/test_hashset.scad>;
 include <util/map/test_hashmap.scad>;
-include <util/test_sort.scad>;
+include <util/test_sorted.scad>;
+include <util/test_binary_search.scad>;
 
 // Voxel
 include <voxel/test_vx_bezier.scad>;

test/util/test_binary_search.scad

@@ -0,0 +1,19 @@
+use <util/sorted.scad>;
+use <util/binary_search.scad>;
+
+module test_binary_search() {
+    echo("==== test_binary_search ====");
+
+    points = [[1, 1], [3, 4], [7, 2], [5, 2]];
+    lt = sorted(points); // [[1, 1], [3, 4], [5, 2], [7, 2]]
+
+    assert(binary_search(lt, [7, 2]) == 3);
+
+    xIs5 = function(elem) elem[0] - 5;
+    assert(binary_search(lt, xIs5) == 2);
+
+    yIs4 = function(elem) elem[1] - 4;
+    assert(binary_search(lt, yIs4) == 1);
+}
+
+test_binary_search();