text: WORK IN PROGRESS
  Floating Point Numbers, Infinities and NaNs
  In preparation for resolving STDCXX-51 this page outlines the platform-specific details describing infinities and NaNs produced as the result of certain floating point calculations, usually triggered by invalid operands.
  libc symbols
  C99 specifies the following interface to infinities and NaNs:
  7.12 Mathematics <math.h>
  -4- The macro INFINITY expands to a constant expression of type float representing positive or unsigned infinity, if available; else to a positive constant of type float that overflows at translation time.
  -5- The macro NAN is defined if and only if the implementation supports quiet NaNs for the float type. It expands to a constant expression of type float representing a quiet NaN.
  7.12.11.2 The nan functions
  -1- Synopsis
  #include <math.h> double nan(const char *tagp); float nanf(const char *tagp); long double nanl(const char *tagp);
  Description
  -2- The call nan("n-char-sequence") is equivalent to strtod("NAN(n-charsequence)", (char**) NULL); the call nan("") is equivalent to strtod("NAN()", (char**) NULL). If tagp does not point to an n-char sequence or an empty string, the call is equivalent to strtod("NAN", (char**) NULL). Calls to nanf and nanl are equivalent to the corresponding calls to strtof and strtold.
  Returns
  -3- The nan functions return a quiet NaN, if available, with content indicated through tagp. If the implementation does not support quiet NaNs, the functions return zero.
  The table below lists the public symbols defined on each platform for Infinity, quiet NaN, and signaling NaN.
  1 Supports all signatures required by C99 and POSIX: float nanf(const char*), double nan(const char*), and long double nanl(const char*).
  2 Recent versions also support the C99 interface.
  printf() formatting
  numeric_limits<double> values/formatting
  Bit Patterns
  The table below shows the bit patterns for Infinity, Quiet NaN, and Signaling NaN on each platform.
  1 Intel and AMD processors set the first fraction bit to 1 for Quiet NaNs and clear it for Signaling NaNs.