Quadratic.f90

SUBROUTINE quadraticFormula(a,b,c,root1,root2,success)
IMPLICIT NONE

! Programmer: Nate Benes
! Purpose: Subroutine to calculate the real roots of a function

REAL, INTENT(IN) :: a,b,c         ! Store the inputs of the function
REAL, INTENT(OUT) :: root1, root2 ! Store the outputs of the function
LOGICAL, INTENT(OUT) :: success   ! variable to indicate whether we can find the root
REAL :: discriminant

discriminant = b**2-4*a*c

! Do some basic validation
IF((a == 0) .OR. (discriminant < 0)) THEN ! We can't solve this function
    success = .FALSE.
    WRITE(*,*) "Program either has complex roots or is not quadratic."
ELSE
    root1 = (-b + SQRT(discriminant))*0.5/a
    root2 = (-b - SQRT(discriminant))*0.5/a
END IF

END SUBROUTINE