Changeset 988Tweet

Timestamp:

Sep 27, 2011, 7:09:28 PM (10 years ago)

Author:

sam

Message:

core: add exp() for real numbers and fix the == operator.

Location:

trunk/src

Files:

• real.cpp (modified) (3 diffs)
• real.h (modified) (1 diff)

trunk/src/real.cpp

@@ -347 +347 @@
 bool real::operator ==(real const &x) const
 {
+    if ((m_signexp << 1) == 0 && (x.m_signexp << 1) == 0)
+        return true;
+
     if (m_signexp != x.m_signexp)
         return false;
@@ -499 +502 @@
 }
 
+real exp(real const &x)
+{
+    int square = 0;
+
+    /* FIXME: this is slow. Find a better way to approximate exp(x) for
+     * large values. */
+    real tmp = x, one = 1.0;
+    while (tmp > one)
+    {
+        tmp.m_signexp--;
+        square++;
+    }
+
+    real ret = 1.0, fact = 1.0, xn = tmp;
+
+    for (int i = 1; i < 100; i++)
+    {
+        fact *= (real)i;
+        ret += xn / fact;
+        xn *= tmp;
+    }
+
+    for (int i = 0; i < square; i++)
+        ret = ret * ret;
+
+    return ret;
+}
+
 void real::print(int ndigits) const
 {
@@ -512 +543 @@
     /* Normalise x so that mantissa is in [1..9.999] */
     int exponent = 0;
-    for (real div = r1, newdiv; true; div = newdiv)
-    {
-        newdiv = div * r10;
-        if (x < newdiv)
+    if (x.m_signexp)
+    {
+        for (real div = r1, newdiv; true; div = newdiv)
         {
-            x /= div;
-            break;
+            newdiv = div * r10;
+            if (x < newdiv)
+            {
+                x /= div;
+                break;
+            }
+            exponent++;
         }
-        exponent++;
-    }
-    for (real mul = 1, newx; true; mul *= r10)
-    {
-        newx = x * mul;
-        if (newx >= r1)
+        for (real mul = 1, newx; true; mul *= r10)
         {
-            x = newx;
-            break;
+            newx = x * mul;
+            if (newx >= r1)
+            {
+                x = newx;
+                break;
+            }
+            exponent--;
         }
-        exponent--;
     }
 

trunk/src/real.h

@@ -56 +56 @@
     friend real fres(real const &x);
     friend real sqrt(real const &x);
+    friend real exp(real const &x);
 
     void print(int ndigits = 150) const;