Select Where: need to select from current selection in JSL

[#1]

I would like to select rows from a data set where I have multiple conditions, but instead of using a single select where statement with "and," I want to loop through my conditions one at a time, selecting from the current selection. This is very straightforward in the select where window (use "select from current selection"). How can I do this in JSL?

For example, I have a list of column names cnames = {"Col1", "Col2", "Col3"} and a list of values cspecs = {"a", "b","c} and I want to select the rows from my data table where Col1 = a, Col2 = b, and Col3 = c. I will loop through the items in cnames and tell it to select from the current selection each time. Thanks!

dt<<

select where(as column(cnames)==cspecs)

[#2]

To select a row without deselecting a previously selected row, combine << Select Where with
<< Select Where and the current selection("extend") argument. This is an alternative to
using an OR statement.
dt << Select Where( age == 14 );
dt << Select Where( sex == "F", current selection("extend"));

msharp,

I am not sure where the syntax you show came from.  The JMP 12.1 Scripting Guide and current online documentation do have the correct text, as shown above. 

Thanks.

Wendy