[GAP Forum] Block matrices problem

[Anvita]

Dear Forum,

I am stuck again :(

Program 1 :
----------------------------------------------
m:=[[1]];
M:=BlockMatrix([[1,2,m],[2,2,m]],2,2);
Display(M);
M*M;
----------------------------------------------

Result 1 :
-------------------------------------------
gap> m:=[[1]];
[ [ 1 ] ]
gap> M:=BlockMatrix([[2,2,m],[1,2,m]],2,2);
<block matrix of dimensions (2*1)x(2*1)>
gap> Display(M);
[ [  0,  1 ],
  [  0,  1 ] ]
gap> M*M;
<block matrix of dimensions (2*1)x(2*1)>
-------------------------------------------

Program 2 :
--------------------------------------
m:=[[1]];
M:=BlockMatrix([[1,2,m],[2,1,m],[2,2,m]],2,2);
Display(M);
M*M;
--------------------------------------

Result 2 :
----------------------------------------------------
gap> m:=[[1]];
[ [ 1 ] ]
gap> M:=BlockMatrix([[2,1,m],[2,2,m],[1,2,m]],2,2);
<block matrix of dimensions (2*1)x(2*1)>
gap> Display(M);
[ [  0,  1 ],
  [  1,  1 ] ]
gap> M*M;
Error, two blocks for position [2][2] called from
BlockMatrix( blocks, bm1!.nrb, bm2!.ncb, bm1!.rpb,
bm2!.cpb, bm1!.zero ) called from
<function>( <arguments> ) called from read-eval-loop
Entering break read-eval-print loop ...
you can 'quit;' to quit to outer loop, or
you can 'return;' to continue
brk>
-----------------------------------------------------


What is wrong with Program 2 as opposed to Program 1 ?

Anvita