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+
+/* @(#)z_frexp.c 1.0 98/08/13 */
+
+/*
+FUNCTION
+ <<frexp>>, <<frexpf>>---split floating-point number
+INDEX
+ frexp
+INDEX
+ frexpf
+
+ANSI_SYNOPSIS
+ #include <math.h>
+ double frexp(double <[val]>, int *<[exp]>);
+ float frexpf(float <[val]>, int *<[exp]>);
+
+TRAD_SYNOPSIS
+ #include <math.h>
+ double frexp(<[val]>, <[exp]>)
+ double <[val]>;
+ int *<[exp]>;
+
+ float frexpf(<[val]>, <[exp]>)
+ float <[val]>;
+ int *<[exp]>;
+
+
+DESCRIPTION
+ All non zero, normal numbers can be described as <[m]> * 2**<[p]>.
+ <<frexp>> represents the double <[val]> as a mantissa <[m]>
+ and a power of two <[p]>. The resulting mantissa will always
+ be greater than or equal to <<0.5>>, and less than <<1.0>> (as
+ long as <[val]> is nonzero). The power of two will be stored
+ in <<*>><[exp]>.
+
+@ifinfo
+<[m]> and <[p]> are calculated so that
+<[val]> is <[m]> times <<2>> to the power <[p]>.
+@end ifinfo
+@tex
+<[m]> and <[p]> are calculated so that
+$ val = m \times 2^p $.
+@end tex
+
+<<frexpf>> is identical, other than taking and returning
+floats rather than doubles.
+
+RETURNS
+<<frexp>> returns the mantissa <[m]>. If <[val]> is <<0>>, infinity,
+or Nan, <<frexp>> will set <<*>><[exp]> to <<0>> and return <[val]>.
+
+PORTABILITY
+<<frexp>> is ANSI.
+<<frexpf>> is an extension.
+
+
+*/
+
+/*****************************************************************
+ * frexp
+ *
+ * Input:
+ * d - floating point value
+ * exp - exponent value
+ *
+ * Output:
+ * A floating point value in the range [0.5, 1).
+ *
+ * Description:
+ * This routine breaks a floating point value into a number f and
+ * an exponent exp such that d = f * 2 ^ exp.
+ *
+ *****************************************************************/
+
+#include "fdlibm.h"
+#include "zmath.h"
+
+#ifndef _DOUBLE_IS_32BITS
+
+double frexp (double d, int *exp)
+{
+ double f;
+ __uint32_t hd, ld, hf, lf;
+
+ EXTRACT_WORDS (hd, ld, d);
+
+ /* Get the exponent. */
+ *exp = ((hd & 0x7ff00000) >> 20) - 1022;
+
+ /* Get the mantissa. */
+ lf = ld;
+ hf = hd & 0x800fffff;
+ hf |= 0x3fe00000;
+
+ INSERT_WORDS (f, hf, lf);
+
+ /* Check for special values. */
+ switch (numtest (f))
+ {
+ case NAN:
+ case INF:
+ errno = EDOM;
+ *exp = 0;
+ return (f);
+ }
+
+ return (f);
+}
+
+#endif /* _DOUBLE_IS_32BITS */