core: implement frexp(), ldexp() and modf() for reals.

src/real.cpp

@@ -770,6 +770,38 @@ real cosh(real const &x)
     return (exp(x) + exp(-x)) >> 1;
 }
 
+real frexp(real const &x, int *exp)
+{
+    if (!x)
+    {
+        *exp = 0;
+        return x;
+    }
+
+    real ret = x;
+    int exponent = (ret.m_signexp & 0x7fffffffu) - (1 << 30) + 1;
+    *exp = exponent + 1;
+    ret.m_signexp -= exponent + 1;
+    return ret;
+}
+
+real ldexp(real const &x, int exp)
+{
+    real ret = x;
+    if (ret)
+        ret.m_signexp += exp;
+    return ret;
+}
+
+real modf(real const &x, real *iptr)
+{
+    real absx = fabs(x);
+    real tmp = floor(absx);
+
+    *iptr = copysign(tmp, x);
+    return copysign(absx - tmp, x);
+}
+
 real copysign(real const &x, real const &y)
 {
     real ret = x;
@@ -1063,6 +1095,32 @@ real atan(real const &x)
     return ret;
 }
 
+real atan2(real const &y, real const &x)
+{
+    if (!y)
+    {
+        if ((x.m_signexp >> 31) == 0)
+            return y;
+        if (y.m_signexp >> 31)
+            return -real::R_PI;
+        return real::R_PI;
+    }
+
+    if (!x)
+    {
+        if (y.m_signexp >> 31)
+            return -real::R_PI;
+        return real::R_PI;
+    }
+
+    /* FIXME: handle the Inf and NaN cases */
+    real z = y / x;
+    real ret = atan(z);
+    if (x < real::R_0)
+        ret += (y > real::R_0) ? real::R_PI : -real::R_PI;
+    return ret;
+}
+
 void real::hexprint() const
 {
     printf("%08x", m_signexp);

src/real.h

@@ -69,7 +69,7 @@ public:
     friend real asin(real const &x);
     friend real acos(real const &x);
     friend real atan(real const &x);
-    /* FIXME: atan2 */
+    friend real atan2(real const &y, real const &x);
 
     /* Hyperbolic functions */
     friend real sinh(real const &x);
@@ -82,7 +82,9 @@ public:
     friend real log(real const &x);
     friend real log2(real const &x);
     friend real log10(real const &x);
-    /* FIXME: frexp ldexp modf */
+    friend real frexp(real const &x, int *exp);
+    friend real ldexp(real const &x, int exp);
+    friend real modf(real const &x, real *iptr);
 
     /* Power functions */
     friend real re(real const &x);