/// <summary>Converts the parameters to a constant day expression </summary>
/// <param name="expr">The function call expressions</param>
public object ToDuration(BindingCallExpr expr)
{
var duration = (string)(expr.ParamList[0]);
var type = (string)expr.ParamList[1];
var token = expr.ParamList[2] as TokenData;
return(Exprs.Duration(duration, type, token));
}