AsRAT(N: INT): RAT
AsRAT(N: RAT): RAT
AsRAT(N: RINGELEM): RAT
Description
If the argument is a rational value this function returns this value as
a RAT, otherwise it throws an error. Note that if the argument is
actually an integer the result is nevertheless a RAT (with denominator 1).
Example
/**/ use P ::= QQ[x,y];
/**/ type(LC(3*x-y));
RINGELEM
/**/ type(AsRAT(LC(3*x-y)));
RAT