Add precision tests and a fix for Math.cosh and Math.sinh.

Per compat-table/compat-table#392 (comment)
paulmillr · Jan 17, 2015 · 6710cd7 · 6710cd7
1 parent cf344e3
commit 6710cd7
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Showing 2 changed files with 8 additions and 2 deletions.
diff --git a/es6-shim.js b/es6-shim.js
@@ -1225,9 +1225,13 @@
     },
 
     sinh: function (value) {
-      value = Number(value);
+      var x = Number(value);
       if (!global_isFinite(value) || value === 0) { return value; }
-      return (Math.exp(value) - Math.exp(-value)) / 2;
+
+      if (Math.abs(x) < 1) {
+        return (Math.expm1(x) - Math.expm1(-x)) / 2;
+      }
+      return (Math.exp(x - 1) - Math.exp(-x - 1)) * Math.E / 2;
     },
 
     tanh: function (value) {

diff --git a/test/math.js b/test/math.js
@@ -169,6 +169,7 @@ describe('Math', function () {
       expect(Math.cosh(22)).to.almostEqual(1792456423.065795780980053377, 1e-5);
       expect(Math.cosh(-10)).to.almostEqual(11013.23292010332313972137);
       expect(Math.cosh(-23)).to.almostEqual(4872401723.1244513000, 1e-5);
+      expect(Math.cosh(-2e-17)).to.equal(1);
     });
   });
 
@@ -315,6 +316,7 @@ describe('Math', function () {
       expect(Math.sinh(-Infinity)).to.equal(-Infinity);
       expect(Math.sinh(-5)).to.almostEqual(-74.20321057778875);
       expect(Math.sinh(2)).to.almostEqual(3.6268604078470186);
+      expect(Math.sinh(-2e-17)).to.equal(-2e-17);
     });
   });