Backport some float repr tests that were missed in issue 7117.

Lib/test/test_float.py

@@ -563,6 +563,55 @@ class ReprTestCase(unittest.TestCase):
             self.assertEqual(v, eval(repr(v)))
         floats_file.close()
 
+    @unittest.skipUnless(getattr(sys, 'float_repr_style', '') == 'short',
+                         "applies only when using short float repr style")
+    def test_short_repr(self):
+        # test short float repr introduced in Python 3.1.  One aspect
+        # of this repr is that we get some degree of str -> float ->
+        # str roundtripping.  In particular, for any numeric string
+        # containing 15 or fewer significant digits, those exact same
+        # digits (modulo trailing zeros) should appear in the output.
+        # No more repr(0.03) -> "0.029999999999999999"!
+
+        test_strings = [
+            # output always includes *either* a decimal point and at
+            # least one digit after that point, or an exponent.
+            '0.0',
+            '1.0',
+            '0.01',
+            '0.02',
+            '0.03',
+            '0.04',
+            '0.05',
+            '1.23456789',
+            '10.0',
+            '100.0',
+            # values >= 1e16 get an exponent...
+            '1000000000000000.0',
+            '9999999999999990.0',
+            '1e+16',
+            '1e+17',
+            # ... and so do values < 1e-4
+            '0.001',
+            '0.001001',
+            '0.00010000000000001',
+            '0.0001',
+            '9.999999999999e-05',
+            '1e-05',
+            # values designed to provoke failure if the FPU rounding
+            # precision isn't set correctly
+            '8.72293771110361e+25',
+            '7.47005307342313e+26',
+            '2.86438000439698e+28',
+            '8.89142905246179e+28',
+            '3.08578087079232e+35',
+            ]
+
+        for s in test_strings:
+            negs = '-'+s
+            self.assertEqual(s, repr(float(s)))
+            self.assertEqual(negs, repr(float(negs)))
+
 @unittest.skipUnless(float.__getformat__("double").startswith("IEEE"),
                      "test requires IEEE 754 doubles")
 class RoundTestCase(unittest.TestCase):