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NAME
     cplxerr complex error - error-handling functions in the  C++
     complex number math library

SYNOPSIS
     #include <complex.h>
     class complex { ... };
     static const complex complex_zero(0.0, 0.0);
     const int SING      = ...;
     const int OVERFLOW  = ...;
     const int UNDERFLOW = ...;
     class c_exception
     {
     public:
          c_exception(char *n, const complex& a1, const complex& a2=complex_zero);
          c_exception(unsigned char *n, const complex& a1, const complex& a2=complex_zero);
          friend int complex_error(c_exception&); // user may override
     private:
          int type;
          char *name;
          complex arg1, arg2;
          complex retval;
     };

DESCRIPTION
     Functions exp(), log(), log10(), sinh(), and  cosh()  invoke
     function  complex_error()  under the conditions described in
     cplxexp(3C++)  and   cplxtrig(3C++).    If   complex_error()
     returns  zero,  the  return values and setting of errno will
     take place as described.  In addition, a message  describing
     the  kind  of error, the function which detected it, and the
     value causing the error will be written to  cerr  (see  ios-
     tream  documentation).   If  complex_error returns non-zero,
     errno is not set and no message is written.

     The default version of complex_error()  just  returns  zero.
     The programmer may supply a replacement version of the func-
     tion to take any action deemed  appropriate.   The  function
     takes one parameter of type ``reference to c_exception'', of
     which the function is a friend.

  class c_exception
     The class consists of the following fields:

     int type
          An integer describing the type of value, which has  one
          of  the  values  below,  declared in the header as con-
          stants:
          SING      argument singularity, such as divide by zero
          OVERFLOW  overflow range error
          UNDERFLOW underflow range error

     char* name
          Points to a null-terminated string containing the  name
          of the function where the error was detected.

     complex arg1, arg2
          The arguments with which  the  function  detecting  the
          error  was  invoked.   (Those  functions  which  invoke
          complex_err() have only one argument, so arg2  will  be
          irrelevant.)

     complex retval
          The default return value for the invoking  function  if
          complex_err() does not set some other value.

     A replacement version of complex_err() should return zero if
     setting  errno  and  writing  to cerr are desired, or return
     non-zero otherwise.  The replacement could also  change  the
     retval  field  of  its  c_exception parameter if the default
     return value is not desired.

EXAMPLE
     Suppose we want errno to be set, but we do not want to write
     anything  to  cerr  (or  anywhere  else).   Our  replacement
     complex_err() will return non-zero,  which  will  prevent  a
     message from being written, but will also prevent errno from
     being set.  Our function will have to set errno itself.
          #include <complex.h>
          int c_exception(c_exception& x)
          {
               switch( x.type ) {
               case UNDERFLOW:
               case OVERFLOW:
                    errno = ERANGE;
                    break;
               case SING:
                    errno = EDOM;
                    break;
               }
               return 1;
          }

SEE ALSO
     cplx.intro(3C++), cartpol(3C++), cplxexp(3C++),
     cplxops(3C++), cplxtrig(3C++), intro(2), ios.intro(3C++),
     C++ Library Reference, Chapter 3, "The Complex Arithmetic
     Library."

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