Primitives, Composition, Abstraction, and Patterns

We will  start  by thinking about  how  the  PCAP  framework applies to computer programs, in general. We may do that by taking in table 3.1, exploring the PCAP concepts in data, functions, and objects.

Data

The primitive data  items in most programming languages are things  like integer variables, ?oating point values, and  strings. We can use those into data  structures  such as lists, dictionaries, arrays and records. Creating  a data  structure  allows  us,  at the  most  simple  level,  to think  of a type  of primitive data  elements as if it were  one thing,  freeing  us from information.   Sometimes, we just think  of a section  of data,  not  in type  of its relaying representation, but  in terms  of what  it shows.  So, we may think  of a set of functions, or a family  tree, without thinking whether it is an array or a list in its basic representation. Abstract data  types  gives a way  of abstracting away  from representational details  and allowing us to focus on what  the data  really means.

Procedures

The primitive procedures of a language are things  like built-in  numeric operations and  basic list application. We may combine these  using  the facilities of the language, such as if and  while, or by using  procedure composition (f(g(x))).  If we try  to abstract away  from  the details  of how a particular calculation is done,  we can describe  a new  function; de?ning a function allows  us to use it for computational programs without thinking about  the information  of how  those  computational jobs get completed.   You can think  of this  process  as essentially creating a new  primitive, which  we may then  use  while  ignoring the information  of how  it is created.  One  way  to save common patterns of abstraction in method is to abstract over functions themselves, with higher-order methods.

Objects

Object-oriented programming provides a number of methods of abstraction and  pattern capture in both  data  and  function. At the most  basic level, objects can be used  as files, combining with primitive data  component. More usually, they give strategies for jointly abstracting a data  representation and the procedures that work  on it. The features of polymorphism and inheritance are particularly important.

Table 3.1          Primitives, combination, abstraction, patterns framework for computer programs