Fortran: Change function based on parameter - function

Question

Is it possible to change the function called for a program based on a parameter value? I'm thinking of something similar to a function overload, the example below shows what I'm thinking. I'm just am wondering if there is a cleaner / better way to do it.
function squareArea(s) result(A)
real :: s, A
A = s*s
end function squareArea
function circleArea(r) result(A)
real :: r, A
A = 3.14159 * r * r
end function circleArea
function Area(shape, dim) result(A)
character(len = *) shape
real dim, A
if (shape == 'circle') then
A = circleArea(dim)
elseif (shape == 'square') then
A = squareArea(dim)
end if
end function Area
program main
character(len = 6) :: sh = 'circle'
real :: r = 1.4
real :: A
A = Area(sh, r)
write(*,*) sh, r, A
end program main

Answer 1

Yes - and you show one possible way.
Fortran 2003 permits overriding of procedures based on the dynamic type of the object used to reference the procedure. Whether this is better/cleaner depends on your circumstances.
MODULE Shapes
IMPLICIT NONE
TYPE, ABSTRACT :: Shape
CONTAINS
PROCEDURE(shape_Area), DEFERRED :: Area
END TYPE Shape
INTERFACE
FUNCTION shape_Area(sh) RESULT(area)
IMPORT :: Shape
IMPLICIT NONE
CLASS(Shape), INTENT(IN) :: sh
REAL :: area
END FUNCTION shape_Area
END INTERFACE
TYPE, EXTENDS(Shape) :: Circle
REAL :: radius
CONTAINS
PROCEDURE :: Area => circle_Area
END TYPE Circle
TYPE, EXTENDS(Shape) :: Square
REAL :: side
CONTAINS
PROCEDURE :: Area => square_Area
END TYPE Square
CONTAINS
FUNCTION circle_Area(sh) RESULT(area)
CLASS(Circle), INTENT(IN) :: sh
REAL :: area
area = 3.14159 * sh%radius**2
END FUNCTION circle_Area
FUNCTION square_Area(sh) RESULT(area)
CLASS(Square), INTENT(IN) :: sh
REAL :: area
area = sh%side**2
END FUNCTION square_Area
END MODULE Shapes
PROGRAM Areas
USE Shapes
IMPLICIT NONE
TYPE(Circle) :: c = Circle(1.4)
TYPE(Square) :: s = Square(1.4)
CHARACTER(*), PARAMETER :: fmt = "(A,G0,' has area ',G0)"
PRINT fmt, 'Circle with radius ', c%radius, c%Area()
PRINT fmt, 'Square with side ', s%side, s%Area()
END PROGRAM Areas