Classes var_lens_other_form and con_lens_other_form cause a matrix to appear to have a different form. They differ from the matrix member function assign_form which genuinely changes a matrix.

With these lenses, the sequence of the elements will not appear to be changed; thus subscripting by sign_int will not be affected, but subscripting by vec_si will reflect a change.

This example program:

#include "SOME_DIRECTORY/mat_gen_dim.h"
using namespace mat_gen_dim;

int main () {
    form const frm_a {blt{2,5},blt{1,3},blt{4,8}};
    cout << "\nfrm_a: " << frm_a;
    cout << "\nfrm_a.count: " << frm_a.count();
    con_matrix<double> mat_a {sub_matrix_linear (frm_a, 5.0)};
    cout << "\nmat_a: " << mat_a;

    form const frm_b {blt{0,6},blt{3,7}};
    cout << "\nfrm_b: " << frm_b;
    cout << "\nfrm_b.count: " << frm_b.count();
    con_lens_other_form<double> aof_b {mat_a, frm_b};
    cout << "\naof_b: " << aof_b;

    form const frm_c {blt{22,46}};
    cout << "\nfrm_c: " << frm_c;
    cout << "\nfrm_c.count: " << frm_c.count();
    con_lens_other_form<double> aof_c {aof_b, frm_c};
    cout << "\naof_c: " << aof_c;

    cout << "\nmat_a (3 1 6) = " << mat_a.get (vec_si {3,1,6});
    cout << "\naof_b (2 4)   = " << aof_b.get (vec_si {2,4});
    cout << "\naof_c (32)    = " << aof_c.get (vec_si {32});

    return 0;
}

frm_a: ( 2 =< 5, 1 =< 3, 4 =< 8 )
frm_a.count: 24
mat_a: 
    ( 2 1 4 ) = 5.214    ( 2 1 5 ) = 5.215    ( 2 1 6 ) = 5.216    ( 2 1 7 ) = 5.217
    ( 2 2 4 ) = 5.224    ( 2 2 5 ) = 5.225    ( 2 2 6 ) = 5.226    ( 2 2 7 ) = 5.227
    ( 3 1 4 ) = 5.314    ( 3 1 5 ) = 5.315    ( 3 1 6 ) = 5.316    ( 3 1 7 ) = 5.317
    ( 3 2 4 ) = 5.324    ( 3 2 5 ) = 5.325    ( 3 2 6 ) = 5.326    ( 3 2 7 ) = 5.327
    ( 4 1 4 ) = 5.414    ( 4 1 5 ) = 5.415    ( 4 1 6 ) = 5.416    ( 4 1 7 ) = 5.417
    ( 4 2 4 ) = 5.424    ( 4 2 5 ) = 5.425    ( 4 2 6 ) = 5.426    ( 4 2 7 ) = 5.427
frm_b: ( 0 =< 6, 3 =< 7 )
frm_b.count: 24
aof_b: 
    ( 0 3 ) = 5.214    ( 0 4 ) = 5.215    ( 0 5 ) = 5.216    ( 0 6 ) = 5.217
    ( 1 3 ) = 5.224    ( 1 4 ) = 5.225    ( 1 5 ) = 5.226    ( 1 6 ) = 5.227
    ( 2 3 ) = 5.314    ( 2 4 ) = 5.315    ( 2 5 ) = 5.316    ( 2 6 ) = 5.317
    ( 3 3 ) = 5.324    ( 3 4 ) = 5.325    ( 3 5 ) = 5.326    ( 3 6 ) = 5.327
    ( 4 3 ) = 5.414    ( 4 4 ) = 5.415    ( 4 5 ) = 5.416    ( 4 6 ) = 5.417
    ( 5 3 ) = 5.424    ( 5 4 ) = 5.425    ( 5 5 ) = 5.426    ( 5 6 ) = 5.427
frm_c: ( 22 =< 46 )
frm_c.count: 24
aof_c: 
    ( 22 ) = 5.214    ( 23 ) = 5.215    ( 24 ) = 5.216    ( 25 ) = 5.217
    ( 26 ) = 5.224    ( 27 ) = 5.225    ( 28 ) = 5.226    ( 29 ) = 5.227
    ( 30 ) = 5.314    ( 31 ) = 5.315    ( 32 ) = 5.316    ( 33 ) = 5.317
    ( 34 ) = 5.324    ( 35 ) = 5.325    ( 36 ) = 5.326    ( 37 ) = 5.327
    ( 38 ) = 5.414    ( 39 ) = 5.415    ( 40 ) = 5.416    ( 41 ) = 5.417
    ( 42 ) = 5.424    ( 43 ) = 5.425    ( 44 ) = 5.426    ( 45 ) = 5.427
mat_a (3 1 6) = 5.316
aof_b (2 4)   = 5.315
aof_c (32)    = 5.316