(libc.info.gz) Complex Numbers

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 20.9 Complex Numbers
 ====================
 
 ISO C99 introduces support for complex numbers in C. This is done with a
 new type qualifier, 'complex'.  It is a keyword if and only if
 'complex.h' has been included.  There are three complex types,
 corresponding to the three real types: 'float complex', 'double
 complex', and 'long double complex'.
 
    To construct complex numbers you need a way to indicate the imaginary
 part of a number.  There is no standard notation for an imaginary
 floating point constant.  Instead, 'complex.h' defines two macros that
 can be used to create complex numbers.
 
  -- Macro: const float complex _Complex_I
      This macro is a representation of the complex number "0+1i".
      Multiplying a real floating-point value by '_Complex_I' gives a
      complex number whose value is purely imaginary.  You can use this
      to construct complex constants:
 
           3.0 + 4.0i = 3.0 + 4.0 * _Complex_I
 
      Note that '_Complex_I * _Complex_I' has the value '-1', but the
      type of that value is 'complex'.
 
 '_Complex_I' is a bit of a mouthful.  'complex.h' also defines a shorter
 name for the same constant.
 
  -- Macro: const float complex I
      This macro has exactly the same value as '_Complex_I'.  Most of the
      time it is preferable.  However, it causes problems if you want to
      use the identifier 'I' for something else.  You can safely write
 
           #include <complex.h>
           #undef I
 
      if you need 'I' for your own purposes.  (In that case we recommend
      you also define some other short name for '_Complex_I', such as
      'J'.)
 

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(libc.info.gz) Arithmetic Functions

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(libc.info.gz) Operations on Complex