#191 Bugfix: round may result in improper coefficient

MikeMcl · MikeMcl · commit d589a0e268f0 · 2022-07-09T19:03:30.000+01:00
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);
 });

Original file line number	Diff line number	Diff line change
`@@ -230,17 +230,18 @@`
`230`	`230`	`rm === 3 && (more \|\| !!xc[0]);`
`231`	`231`
`232`	`232`	`// Remove any digits after the required precision.`
`233`		`- xc.length = sd--;`
	`233`	`+ xc.length = sd;`
`234`	`234`
`235`	`235`	`// Round up?`
`236`	`236`	`if (more) {`
`237`	`237`
`238`	`238`	`// Rounding up may mean the previous digit has to be rounded up.`
`239`		`- for (; ++xc[sd] > 9;) {`
	`239`	`+ for (; ++xc[--sd] > 9;) {`
`240`	`240`	`xc[sd] = 0;`
`241`		`- if (!sd--) {`
	`241`	`+ if (sd === 0) {`
`242`	`242`	`++x.e;`
`243`	`243`	`xc.unshift(1);`
	`244`	`+ break;`
`244`	`245`	`}`
`245`	`246`	`}`
`246`	`247`	`}`
Original file line number	Diff line number	Diff line change
`@@ -227,17 +227,18 @@ function round(x, sd, rm, more) {`
`227`	`227`	`rm === 3 && (more \|\| !!xc[0]);`
`228`	`228`
`229`	`229`	`// Remove any digits after the required precision.`
`230`		`- xc.length = sd--;`
	`230`	`+ xc.length = sd;`
`231`	`231`
`232`	`232`	`// Round up?`
`233`	`233`	`if (more) {`
`234`	`234`
`235`	`235`	`// Rounding up may mean the previous digit has to be rounded up.`
`236`		`- for (; ++xc[sd] > 9;) {`
	`236`	`+ for (; ++xc[--sd] > 9;) {`
`237`	`237`	`xc[sd] = 0;`
`238`		`- if (!sd--) {`
	`238`	`+ if (sd === 0) {`
`239`	`239`	`++x.e;`
`240`	`240`	`xc.unshift(1);`
	`241`	`+ break;`
`241`	`242`	`}`
`242`	`243`	`}`
`243`	`244`	`}`