decimalToPrecision: proper rounding for equidistant digits + test for…

… that (ccxt#2407)
ngugc · Mar 30, 2018 · fe16d98 · fe16d98
1 parent e57cfc7
commit fe16d98
Show file tree

Hide file tree

Showing 2 changed files with 9 additions and 3 deletions.
diff --git a/js/base/functions/number.js b/js/base/functions/number.js
@@ -159,8 +159,8 @@ const decimalToPrecision = (x, roundingMode
 
             if (i >= (precisionStart + numPrecisionDigits)) {
                 c = (roundingMode === ROUND)
-                        ? ((c > FIVE) ? (NINE + 1) : ZERO) // single-digit rounding
-                        : ZERO                             // "floor" to zero
+                        ? ((c >= FIVE) ? (NINE + 1) : ZERO) // single-digit rounding
+                        : ZERO                              // "floor" to zero
             }
             if (c > NINE) { c = ZERO; memo = 1; }
             else memo = 0

diff --git a/js/test/base/functions/test.number.js b/js/test/base/functions/test.number.js
@@ -68,7 +68,7 @@ it ('decimalToPrecision: rounding (to N digits after dot)', () => {
     equal (decimalToPrecision ('12.3456',     ROUND,   4, DECIMAL_PLACES),  '12.3456')
     equal (decimalToPrecision ('12.3456',     ROUND,   3, DECIMAL_PLACES),  '12.346')
     equal (decimalToPrecision ('12.3456',     ROUND,   2, DECIMAL_PLACES),  '12.35')
-    equal (decimalToPrecision ('12.3456',     ROUND,   1, DECIMAL_PLACES),  '12.3')
+    equal (decimalToPrecision ('12.3456',     ROUND,   1, DECIMAL_PLACES),  '12.4') // 12.35 → 12.4 (see the "rounding for equidistant digits" test)
     equal (decimalToPrecision ('12.3456',     ROUND,   0, DECIMAL_PLACES),  '12')
 //  equal (decimalToPrecision ('12.3456',     ROUND,  -1, DECIMAL_PLACES),  '10')  // not yet supported
 //  equal (decimalToPrecision ('123.456',     ROUND,  -1, DECIMAL_PLACES), '120')  // not yet supported
@@ -122,4 +122,10 @@ it ('decimalToPrecision: without dot / trailing dot', () => {
     equal (decimalToPrecision ('123.', TRUNCATE, 5, DECIMAL_PLACES, PAD_WITH_ZERO), '123.00000')
 })
 
+it ('decimalToPrecision: rounding for equidistant digits', () => {
+
+    equal (decimalToPrecision ('12.54', ROUND, 1, DECIMAL_PLACES), '12.5')
+    equal (decimalToPrecision ('12.55', ROUND, 1, DECIMAL_PLACES), '12.6')
+})
+
 /*  ------------------------------------------------------------------------ */