Introduction to Cognitive Science-Assignment: 02

DATA TYPES IN PROLOG

• Atom
• Structure
• Variables

Atom

An atom, in Prolog, means a single data item. It may be of one of three types:

·         a string atom, like 'This is a string' or

·         a symbol, like likes, john, and pizza, in likes(john, pizza). Atoms of this type must start with a lower case letter. They can include digits (after the initial lower-case letter) and the underscore character (_).

·         strings of special characters, like <--->, ..., ===>. When using atoms of this type, some care is needed to avoid using strings of special characters with a predefined meaning, like the neck symbol :-, the cut symbol !, and various arithmetic and comparision operators.
The available special characters for constructing this class of atom are: +, -, *, /, <, >, =, :, ., &, _, and ~.

Numbers in Prolog, are not considered to be atoms. Numbers used in prolog are integers and real numbers.

Variables:

A variable in Prolog is a string of letters, digits, and underscores (_) beginning either with a capital letter or with an underscore. Examples:

X, Sister, _, _thing, _y47, First_name, Z2

The variable _ is used as a "don't-care" variable, when we don't mind what value the variable has. For example:

I

s_a_parent(X) :- father_of(X, _).
is_a_parent(X) :- mother_of(X, _).

An underscore '_' also known as anonymous variable is used in clauses when a variable need not be inferred to more than once.

That is, X is a parent if they are a father or a mother, but we don't need to know who they are the father or mother of, to establish that they are a parent.

Structures

Structures in Prolog are simply objects that have several components, but are treated as a single object. Suppose that we wish to represent a date in Prolog - dates are usually expressed using a day, a month, and a year, but viewed as a single object.

For example:

date(21, mar, 2004)

Structures may be nested, too - the following example groups a name and a date, perhaps the person's date of birth:

persondata(name(smith, john), date(28, feb, 1963))

List

A list in Prolog is written as a comma-separated sequence of items, between square brackets. For example, [1, 2, 3] is a list.

The empty list is written [].

A list with just a single item, say the number 7, is written [7].

Annaaaa

Jack

Mya amm

Vkeyt

[ ]

Arithmetic Operators 

SYMBOLS         OPERATION

+                      Addition

-                       Subtraction

*                      Multiplication

/                       Real division

//                      Integer division

mod                  Modulus

**                     Power

Q1. Write a program to find the factorial of any number. Test it with 11.

PREDICATES

factorial(integer,integer)

CLAUSES

factorial(0,1).

factorial(N,F):-N>0, N1=N-1,factorial(N1,F1),F=N*F1.

GOAL

factorial(11,F).

Output:

Q2. Write a program to find the Fibonacci series of the number being entered. Test it for number 10.

         

PREDICATES

fibonacii(integer,integer)

CLAUSES

fibonacii(0,1).

fibonacii(1,1).

fibonacii(N,F):-N>1,N1=N-1,N2=N- 2,fibonacii(N1,F1),fibonacii(N2,F2),F=F1+F2.

GOAL

fibonacii(10,F).

Output:

Q3. Define a predicate to output the values of the squares of the integer from N1 to N2 inclusive and test it with N1=6 and N2=12.

PREDICATES

testloop(integer)

CLAUSES

testloop(5).

testloop(N):-N>=6,write("square of "),write(N),write(" is "),N1=N*N,write(N1),nl,M=N-1,testloop(M).

GOAL

testloop(12).    

Output:

  

CONCLUSION/DISCUSSION:

Thus using visual Prolog program the given programs were tested and verified successfully.