!Name: Nicholas Farkash
!Purpose: To write a program with a block if construct to evaluate a
!           piecewise function of two variables.
!Date: September 22nd, 2021
!Due: September 27th, 2021 at 6:00PM

program HW_5
  implicit none

  real :: x                                 ! Input Variable 1
  real :: y                                 ! Input Variable 2
  real :: answer                            ! Value of function evaluated
  
  write(*,*) "Please enter real values for x and y."
  read(*,*) x, y           ! Read in Variables 1 and 2      

  if( (x**2 + y**2) < (1.0e0)) then
     answer =  -1.0e0 + x**2 + y**2
        ! Evaluate when x**2 + y**2 < 1
     
  elseif( (1.0e0) <= (x**2 + y**2) .and. (x**2 + y**2) < (2.0e0) ) then
     answer = (exp( x**2 + y**2 - 1.0e0)) - 1.0e0
        ! Evaluate when 1 <= x**2 + y**2 < 2
      
  else
     answer = exp(1.0e0) - 1.0e0 + sin( x**2 + y**2 - 2.0e0)
        ! Evaluate when all other statements are false (x**2 + y**2 >= 2)

  endif

  write(*,*) answer        ! Output the value of answer         
  
  stop 0                   ! Stop execution and return 0
end program HW_5