4.3 def

Objects may be defined without a specific type: they inherit their type from the first assignment to them. E.g., ideal i=x,y,z; def j=i^2; defines the ideal i^2 with the name j.

Note: Unlike other assignments a ring as an untyped object is not a copy but another reference to the same (possibly unnamed) ring. This means that entries in one of these rings appear also in the other ones. The following defines a ring s which is just another reference (or name) for the basering r. The name basering is an alias for the current ring.

ring r=32003,(x,y,z),dp; poly f = x; def s=basering; setring s; nameof(basering); ==> s listvar(); ==> // s [0] *ring ==> // f [0] poly ==> // r [0] ring(*) poly g = y; kill f; listvar(r); ==> // r [0] ring(*) ==> // g [0] poly ring t=32003,(u,w),dp; def rt=r+t; rt; ==> // characteristic : 32003 ==> // number of vars : 5 ==> // block 1 : ordering dp ==> // : names x y z ==> // block 2 : ordering dp ==> // : names u w ==> // block 3 : ordering C

This reference to a ring with def is useful if the basering is not local to the procedure (so it cannot be accessed by its name) but one needs a name for it (e.g., for a use with setring or map). setring r; does not work in this case, because r may not be local to the procedure.

4.3.1 def declarations