1 files changed, 74 insertions, 0 deletions
diff --git a/js/src/tests/ecma_6/Math/shell.js b/js/src/tests/ecma_6/Math/shell.js
new file mode 100644
index 000000000..d423c0814
--- /dev/null
+++ b/js/src/tests/ecma_6/Math/shell.js
@@ -0,0 +1,74 @@
+// The nearest representable values to +1.0.
+const ONE_PLUS_EPSILON = 1 + Math.pow(2, -52);  // 0.9999999999999999
+const ONE_MINUS_EPSILON = 1 - Math.pow(2, -53);  // 1.0000000000000002
+
+{
+    var fail = function (msg) {
+        var exc = new Error(msg);
+        try {
+            // Try to improve on exc.fileName and .lineNumber; leave exc.stack
+            // alone. We skip two frames: fail() and its caller, an assertX()
+            // function.
+            var frames = exc.stack.trim().split("\n");
+            if (frames.length > 2) {
+                var m = /@([^@:]*):([0-9]+)$/.exec(frames[2]);
+                if (m) {
+                    exc.fileName = m[1];
+                    exc.lineNumber = +m[2];
+                }
+            }
+        } catch (ignore) { throw ignore;}
+        throw exc;
+    };
+
+    var ENDIAN;  // 0 for little-endian, 1 for big-endian.
+
+    // Return the difference between the IEEE 754 bit-patterns for a and b.
+    //
+    // This is meaningful when a and b are both finite and have the same
+    // sign. Then the following hold:
+    //
+    //   * If a === b, then diff(a, b) === 0.
+    //
+    //   * If a !== b, then diff(a, b) === 1 + the number of representable values
+    //                                         between a and b.
+    //
+    var f = new Float64Array([0, 0]);
+    var u = new Uint32Array(f.buffer);
+    var diff = function (a, b) {
+        f[0] = a;
+        f[1] = b;
+        //print(u[1].toString(16) + u[0].toString(16) + " " + u[3].toString(16) + u[2].toString(16));
+        return Math.abs((u[3-ENDIAN] - u[1-ENDIAN]) * 0x100000000 + u[2+ENDIAN] - u[0+ENDIAN]);
+    };
+
+    // Set ENDIAN to the platform's endianness.
+    ENDIAN = 0;  // try little-endian first
+    if (diff(2, 4) === 0x100000)  // exact wrong answer we'll get on a big-endian platform
+        ENDIAN = 1;
+    assertEq(diff(2,4), 0x10000000000000);
+    assertEq(diff(0, Number.MIN_VALUE), 1);
+    assertEq(diff(1, ONE_PLUS_EPSILON), 1);
+    assertEq(diff(1, ONE_MINUS_EPSILON), 1);
+
+    var assertNear = function assertNear(a, b, tolerance=1) {
+        if (!Number.isFinite(b)) {
+            fail("second argument to assertNear (expected value) must be a finite number");
+        } else if (Number.isNaN(a)) {
+            fail("got NaN, expected a number near " + b);
+        } else if (!Number.isFinite(a)) {
+            if (b * Math.sign(a) < Number.MAX_VALUE)
+                fail("got " + a + ", expected a number near " + b);
+        } else {
+            // When the two arguments do not have the same sign bit, diff()
+            // returns some huge number. So if b is positive or negative 0,
+            // make target the zero that has the same sign bit as a.
+            var target = b === 0 ? a * 0 : b;
+            var err = diff(a, target);
+            if (err > tolerance) {
+                fail("got " + a + ", expected a number near " + b +
+                     " (relative error: " + err + ")");
+            }
+        }
+    };
+}