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5.1.137 rvar
Syntax:
rvar ( name )
rvar ( poly_expression )
rvar ( string_expression )
Type:
- int
Purpose:
- returns the number of the variable if the name/polynomial is a ring variable of the
basering or if the string is the name of a ring variable of the
basering; returns 0 if not. Hence the return value of
rvar can
also be used in a boolean context to check whether the variable exists.
Example:
| ring r=29,(x,y,z),lp;
rvar(x);
==> 1
rvar(r);
==> 0
rvar(y);
==> 2
rvar(var(3));
==> 3
rvar("x");
==> 1
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See
defined;
ring;
var;
varstr.
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