+<p>When using the hexadecimal form, constants of types float and double are
+represented using the 16-digit form shown above (which matches the IEEE754
+representation for double); float values must, however, be exactly representable
+as IEE754 single precision.
+Hexadecimal format is always used for long
+double, and there are three forms of long double. The 80-bit
+format used by x86 is represented as <tt>0xK</tt>
+followed by 20 hexadecimal digits.
+The 128-bit format used by PowerPC (two adjacent doubles) is represented
+by <tt>0xM</tt> followed by 32 hexadecimal digits. The IEEE 128-bit
+format is represented
+by <tt>0xL</tt> followed by 32 hexadecimal digits; no currently supported
+target uses this format. Long doubles will only work if they match
+the long double format on your target. All hexadecimal formats are big-endian
+(sign bit at the left).</p>