Identity matrix intrinsic

[jacobwilliams]

An intrinsic to define an identity matrix would be nice. For example, Matlab has this.

Say:

real(wp),dimension(4,4),parameter :: I = eye(4)

For example, currently, to do this we have to have to do something like this:

real(wp),dimension(4,4),parameter :: I = reshape([1.0_wp,0.0_wp,0.0_wp,0.0_wp,&
                                                  0.0_wp,1.0_wp,0.0_wp,0.0_wp,&
                                                  0.0_wp,0.0_wp,1.0_wp,0.0_wp,&
                                                  0.0_wp,0.0_wp,0.0_wp,1.0_wp],[4,4])

Related maybe to #102.

[FortranFan]

See also #14.

[Leonard-Reuter]

I agree. But well, then there is this solution: =)

integer :: i
integer, parameter :: n = 4  ! dimension of the identity matrix
real(wp), parameter :: I(n,n) = RESHAPE([ (MERGE(1._wp, 0._wp, i/n==MOD(i,n)), i=0, n**2-1) ], [n,n])