## 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 |  |

User manual for Singular version 4-0-3, 2016, generated by texi2html.