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Constrained genericity: Difference between revisions
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successful eat
</lang>
=={{header|Fortran}}==
In Fortran all checkes are done at compile time, in particular a dummy argument has to conform class.
<lang fortran>
module cg
implicit none
type, abstract :: eatable
end type eatable
type, extends(eatable) :: carrot_t
end type carrot_t
type :: brick_t; end type brick_t
type :: foodbox
class(eatable), allocatable :: food
contains
procedure, public :: add_item => add_item_fb
end type foodbox
contains
subroutine add_item_fb(this, f)
class(foodbox), intent(inout) :: this
class(eatable), intent(in) :: f
allocate(this%food, source=f)
end subroutine add_item_fb
end module cg
program con_gen
use cg
implicit none
type(carrot_t) :: carrot
type(brick_t) :: brick
type(foodbox) :: fbox
! Put a carrot into the foodbox
call fbox%add_item(carrot)
! Try to put a brick in - results in a compiler error
call fbox%add_item(brick)
end program con_gen
</lang>
{{out}}
ifort -o cg cg.f90
<pre>
cg.f90(40): error #6633: The type of the actual argument differs from the type of the dummy argument. [BRICK]
call fbox%add_item(brick)
</pre>
gfortran -o cg cg.f90
<pre>
cg.f90:41.23:
call fbox%add_item(brick)
1
Error: Type mismatch in argument 'f' at (1); passed TYPE(brick_t) to CLASS(eatable)
</pre>
=={{header|Go}}==
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