Selecting a name of a structure value results in another name, which is known as a sub-name. For example, given the following structure mode:
mode node = struct (int data, ref int next);
And a name of a value of mode node:
node anode := (0, nil);
Then selecting the field data of the
structure name yields a sub-name with mode ref int:
data of anode := 100; print ((data of anode))
It is said that the mode ref node is “endowed
with sub-names”.