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4.8.4 Indeterminates
An indeterminate is represented by a name consisting of either a single lower case letter or a lower case letter followed by one or more indices. For example, x, x[1], x[1,2,3] are legal (and different) indeterminates, as is x[2I,2I+1] if I is an integer variable.

When creating a ring the indeterminates are listed, optionally separated by commas: lack of separating commas is now obsolescent and might be unacceptable in future versions. Indeterminates with indices are formed with the syntax: x[R_1,...,R_n], where x stands for any lower case letter and each R_i has the form A..B for integers A <= B.

  Use R ::= QQ[xyz];  -- this syntax is obsolescent
  Use R ::= QQ[x,y,z];

  Use R ::= QQ[x[1..2,4..8],y[1..3],u,v];
[x[1,4], x[1,5], x[1,6], x[1,7], x[1,8], x[2,4], x[2,5], x[2,6],
x[2,7], x[2,8], y[1], y[2], y[3], u, v]