new function sort3i

README.md

@@ -322,6 +322,11 @@ Return an array containing the 3 items in ascending order.  Much faster than `[a
     qibl.sort3(3, 1, 2);
     // => [1, 2, 3]
 
+### qibl.sort3i( array, i, j, k )
+
+Rearrange the array contents at offsets i, j and k so that array[i], array[j] and array[k]
+are in ascending order.
+
 ### qibl.newBuf( arg, encodingOrOffset, length )
 
 Construct a Buffer like `new Buffer()` used to before it was deprecated.  Note that with
@@ -424,7 +429,7 @@ else a Buffer for Buffer data.  The callback is invoked when the 'end' event is
 Changelog
 ---------
 
-- 1.6.0 - new function `entries`, new undocumented function `str_locate`, fix get/setIterator property name,
+- 1.6.0 - new function `entries`, `sort3i`, new undocumented function `str_locate`, fix get/setIterator property name,
           speed up iterators
 - 1.5.1 - fix getProperty, do not prevent multiple callbacks from readBody
 - 1.5.0 - new functions `derive`, `varargsRenamed`, `isMethodContext`, `readBody`;

qibl.js

@@ -63,6 +63,7 @@ var qibl = module.exports = {
     subsample: subsample,
     qsearch: qsearch,
     sort3: sort3,
+    sort3i: sort3i,
     curry: curry,
     once: once,
     tryRequire: tryRequire,
@@ -321,6 +322,14 @@ function sort3( a, b, c ) {
     // descending:
     // return (b > a) ? sort3(b, a, c) : (c > a ? [c, a, b] : c > b ? [a, c, b] : [a, b, c]);
 }
+function sort3i( arr, i, j, k ) {
+    if (arr[j] < arr[i]) { swapi(arr, i, j); sort3i(arr, i, j, k) }
+    if (arr[k] < arr[i]) { var t = arr[k]; arr[k] = arr[j]; arr[j] = arr[i]; arr[i] = t; return }
+    if (arr[k] < arr[j]) swapi(arr, j, k);
+}
+function swapi( a, i, j ) {
+    var t = a[i]; a[i] = a[j]; a[j] = t;
+}
 
 // See also `qprintf`.
 function str_repeat( str, n ) {

test-qibl.js

@@ -626,6 +626,17 @@ module.exports = {
         t.done();
     },
 
+    'sort3i': function(t) {
+        for (var i = 0; i < 1000; i++) {
+            var arr = [Math.random(), Math.random(), Math.random()];
+            qibl.sort3i(arr, 0, 1, 2);
+            t.ok(arr[0] <= arr[1] && arr[1] <= arr[2], "not sorted: " + arr);
+            qibl.sort3i(arr, 2, 1, 0);
+            t.ok(arr[0] >= arr[1] && arr[1] >= arr[2], "not sorted: " + arr);
+        }
+        t.done();
+    },
+
     'str_repeat should repeat': function(t) {
         var tests = [
             [ "", 2, "" ],