68.5 MeatAxeMat

MeatAxeMat( mat [, F ] [, abstract ] [, filename ] )

returns a MeatAxe matrix corresponding to the matrix mat, viewed over the finite field F, or over the field of all entries of mat.

If mat is already a MeatAxe matrix then the call means that it shall now be viewed over the field F which may be smaller or larger than the field mat was viewed over.

The optional argument abstract is an element of a free algebra (see chapter Finitely Presented Algebras) that represents the matrix in terms of generators.

If the optional argument filename is given, the MeatAxe matrix is written to the file with this name; a matrix constructed this way will not be removed by a call to MeatAxe.Unbind. Otherwise GAP creates a temporary file under the directory MeatAxe.direc.

MeatAxeMat( perm, F, dim [,abstract][,filename] )

does the same for a permutation perm that shall be converted into a permutation matrix over the field F, with dim[1] rows and dim[2] columns.

MeatAxeMat( file, F, dim [, abstract ] )

is the MeatAxe matrix stored on file file, viewed over the field F, with dimensions dim, and representation abstract. This may be used to make a shallow copy of a MeatAxe matrix, or to notify MeatAxe matrices that were not produced by GAP. Such matrices are not removed by calls to MeatAxe.Unbind.

Note: No field change is allowed here.

    gap> f:= GF(2);;
    gap> m:= [ [ 0, 1, 0 ], [ 0, 0, 1 ], [ 1, 0, 0 ] ] * f.one;;
    gap> m1:= MeatAxeMat( m, "file2" );
    MeatAxeMat( "/var/tmp/tmp.005046/file2", GF(2), [ 3, 3 ] )
    gap> p:= (1,2,3);;
    gap> m2:= MeatAxeMat( p, f, [ 3, 3 ], "file" );
    MeatAxeMat( "/var/tmp/tmp.005046/file", GF(2), [ 3, 3 ] )
    gap> Display( m2 );
    MeatAxe.Matrix := [
    [0,1,0],
    [0,0,1],
    [1,0,0]
    ]*Z(2);
    gap> n:= MeatAxeMat( "file", f, [ 3, 3 ] );; # just notify a matrix 

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