#191 Bugfix: round may result in improper coefficient

MikeMcl · Jul 9, 2022 · d589a0e · d589a0e
1 parent f842264
commit d589a0e
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Showing 3 changed files with 11 additions and 6 deletions.
diff --git a/big.js b/big.js
@@ -230,17 +230,18 @@
         rm === 3 && (more || !!xc[0]);
 
       // Remove any digits after the required precision.
-      xc.length = sd--;
+      xc.length = sd;
 
       // Round up?
       if (more) {
 
         // Rounding up may mean the previous digit has to be rounded up.
-        for (; ++xc[sd] > 9;) {
+        for (; ++xc[--sd] > 9;) {
           xc[sd] = 0;
-          if (!sd--) {
+          if (sd === 0) {
             ++x.e;
             xc.unshift(1);
+            break;
           }
         }
       }

diff --git a/big.mjs b/big.mjs
@@ -227,17 +227,18 @@ function round(x, sd, rm, more) {
       rm === 3 && (more || !!xc[0]);
 
     // Remove any digits after the required precision.
-    xc.length = sd--;
+    xc.length = sd;
 
     // Round up?
     if (more) {
 
       // Rounding up may mean the previous digit has to be rounded up.
-      for (; ++xc[sd] > 9;) {
+      for (; ++xc[--sd] > 9;) {
         xc[sd] = 0;
-        if (!sd--) {
+        if (sd === 0) {
           ++x.e;
           xc.unshift(1);
+          break;
         }
       }
     }

diff --git a/test/methods/round.js b/test/methods/round.js
@@ -5286,4 +5286,7 @@ test('round', function () {
   t('0', '98765000', -10, 1);
   t('0', '98765000', -10, 2);
   t('10000000000', '98765000', -10, 3);
+
+  // #191
+  test.isTrue(new Big('9.9').round().c['-1'] === u);
 });