Extend

The extend operation adds an attribute to a table and populates it with values according to some formula.

The rename >> symbol becomes an extend operator if it has nothing on the left inside of a projection expression. Let’s say we have a table of Celsius temperatures and we want to add a column of equivalent Fahrenheit values.

ftemps #= ctemps[>>Fahrenheit(Celsius.toFdeg())].(Fahrenheit)

We start with the ctemps table which as only one column named Celsius. It is extended by adding a Fahrenheit column who’s value will be the Celsius temperature with the toFdeg conversion invoked. We assume that the temperature scalar provides this conversion operation.