Currently, when Pipe object is printed, it examines if the output value is NULL to determine whether the value should be printed. As a result, only NULL value will not be printed.
However, some functions return invisible value, (e.g. hist()). print.Pipe() should inherit the visibility of the value in Pipe.
Currently, when
Pipeobject is printed, it examines if the output value isNULLto determine whether the value should be printed. As a result, onlyNULLvalue will not be printed.However, some functions return invisible value, (e.g.
hist()).print.Pipe()should inherit the visibility of the value in Pipe.See http://stackoverflow.com/questions/25867560/how-can-i-know-if-a-value-is-invisibly-returned-by-a-function.