Data abstraction guide
Data abstraction isolates the use of a composite data from the details of how the data object is constructed from more basic data objects.
sequence pair
The basic procedure cons takes two parameters and returns a conforming data object containing these two parameters as its components.
example:
Data objects constructed from sequence pairs are called table-structured data
abstract barrier
The basic idea of data abstraction is to identify a set of operations for each type of data object, so that all operations on such data objects can be expressed based on them, and only use them when operating these data objects.
what data means
Example--Picture abstraction:
answer. Mainly depends on the way this unfolds
Hierarchical data and closure properties