[gnome-calculator] Use double instead of float for better precision ln (fixes bug 702817).

[Arth Patel <arthpatel src gnome org>]

commit 6eb0f2b5e6df456a97a796b35d811376a69679e0
Author: Daniel Renninghoff <daniel danielrenninghoff com>
Date:   Wed Feb 26 03:02:56 2014 +0100

    Use double instead of float for better precision ln (fixes bug 702817).
    
    ln now also works for e^x, where x >= 3.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=702817

 src/number.vala |   59 ++----------------------------------------------------
 1 files changed, 3 insertions(+), 56 deletions(-)
---
diff --git a/src/number.vala b/src/number.vala
index 6db386e..89b5a01 100644
--- a/src/number.vala
+++ b/src/number.vala
@@ -2103,10 +2103,10 @@ public class Number
             /* REMOVE EXPONENT TO AVOID FLOATING-POINT OVERFLOW */
             var e = t1.re_exponent;
             t1.re_exponent = 0;
-            var rx = t1.to_float_old ();
+            var rx = t1.to_double ();
             t1.re_exponent = e;
-            var rlx = (float) (Math.log (rx) + e * Math.log (BASE));
-            t2 = new Number.float (-(float)rlx);
+            var rlx = Math.log (rx) + e * Math.log (BASE);
+            t2 = new Number.double (-rlx);
 
             /* UPDATE Z AND COMPUTE ACCURATE EXP OF APPROXIMATE LOG */
             z = z.subtract (t2);
@@ -2120,59 +2120,6 @@ public class Number
         return z;
     }
 
-    // FIXME: This is here becase ln e breaks if we use the symmetric to_float
-    private float to_float_old ()
-    {
-        if (is_zero ())
-            return 0f;
-
-        var z = 0f;
-        var i = 0;
-        for (; i < T; i++)
-        {
-            z = BASE * z + re_fraction[i];
-
-            /* CHECK IF FULL SINGLE-PRECISION ACCURACY ATTAINED */
-            if (z + 1.0f <= z)
-                break;
-        }
-
-        /* NOW ALLOW FOR EXPONENT */
-        z = (float) (z * mppow_ri (BASE, re_exponent - i - 1));
-
-        if (re_sign < 0)
-            return -z;
-        else
-            return z;
-    }
-
-    private double mppow_ri (float ap, int bp)
-    {
-        if (bp == 0)
-            return 1.0f;
-
-        if (bp < 0)
-        {
-            if (ap == 0)
-                return 1.0f;
-            bp = -bp;
-            ap = 1 / ap;
-        }
-
-        var pow = 1.0;
-        while (true)
-        {
-            if ((bp & 01) != 0)
-                pow *= ap;
-            if ((bp >>= 1) != 0)
-                ap *= ap;
-            else
-                break;
-        }
-
-        return pow;
-    }
-
     /*  RETURNS MP Y = Ln (1+X) IF X IS AN MP NUMBER SATISFYING THE
      *  CONDITION ABS (X) < 1/B, ERROR OTHERWISE.
      *  USES NEWTONS METHOD TO SOLVE THE EQUATION