!Name: Nicholas Farkash
!Purpose: To learn how to use nested if constructs (and also to take down
        ! a zombie target!)
!Date: September 28th, 2021
!Due: October 1st, 2021

program HW_6
  implicit none

  real :: xcoord               ! distance on x axis from ship to zombie in km.
  real :: ycoord               ! distance on y axis from ship to zombie in km.
  character(9) :: quadrant     ! The quadrant the zombie is located.
  real :: range                ! Distance from ship to zombie.
  real :: bearing              ! Angle zombie is at with respect to true North.
  real, PARAMETER :: PI = 3.14159265
  
  write(*,*) "Enter the coordinates of the attacking zombie in", &
             " kilometers relative to the ship!"
  read(*,*) xcoord, ycoord    ! Read in values for zombie coordinates

  if (xcoord > 0.0) then  
     if (ycoord > 0.0) then
        quadrant = "Northeast"         ! Zombie is in the Northeast quadrant
     elseif (ycoord < 0.0) then 
        quadrant = "Southeast"         ! Zombie is in the Southeast quadrant
     endif
  elseif (xcoord < 0.0) then
     if (ycoord > 0.0) then
        quadrant = "Northwest"         ! Zombie is in the Northwest quadrant
     elseif (ycoord < 0.0) then
        quadrant = "Southwest"         ! Zombie is in the Southwest quadrant
     endif
  endif

   range = sqrt( (xcoord ** 2) + (ycoord ** 2) )          ! Distance to target
   bearing = abs(  atan(ycoord / xcoord) * (180.0 / PI) ) ! Angle of target

   if (quadrant == "Northeast") then          ! Calculate the angle relative
      bearing = bearing                       ! to North
   elseif (quadrant == "Southeast") then
      bearing = 90.0 + bearing
   elseif (quadrant == "Southwest") then
      bearing = 180.0 + bearing
   elseif (quadrant == "Northwest") then
      bearing = 270.0 + bearing
   endif
   
   write(*,*) "The zombie is",range,"kilometers away at a bearing of" &
              ,bearing,"degrees. This is in the ",quadrant," quadrant."

  stop 0
end program HW_6