MA01AD

Complex square root of a complex number in real arithmetic

Purpose

  To compute the complex square root YR + i*YI of a complex number
  XR + i*XI  in real arithmetic.  The returned result is so that
  YR >= 0.0  and  SIGN(YI) = SIGN(XI).

      SUBROUTINE MA01AD( XR, XI, YR, YI )
C     .. Scalar Arguments ..
      DOUBLE PRECISION  XR, XI, YR, YI

Input/Output Parameters

  XR      (input) DOUBLE PRECISION
  XI      (input) DOUBLE PRECISION
          These scalars define the real and imaginary part of the
          complex number of which the square root is sought.

  YR      (output) DOUBLE PRECISION
  YI      (output) DOUBLE PRECISION
          These scalars define the real and imaginary part of the
          complex square root.

  The complex square root YR + i*YI of the complex number XR + i*XI
  is computed in real arithmetic, taking care to avoid overflow.

  Adapted from EISPACK subroutine CSROOT.

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Program Text

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