1. introduction

2.arithmetic

3. if-else - CLICK

4.loop

5. List: click

6. CBCS university assignments CLICK

7. Read value from user:

1. BIRYINI IS A FOOD.

QUESTION:?

A) IS BIRIYANI A FOOD?

B) IS MOMO A FOOD?

CLICK HERE

BIRYINI IS A FOOD.

MOMO IS A FOOD.

QUESTION:?

A) HOW MANY FOODS?

B) IF ALL FOODS ARE MEAL , THEN DISPLAY ALL MEALS.

CLICK HERE

BIRYINI IS A FOOD.

MOMO IS A FOOD.

BIRIYANI IS A LUNCH.

QUESTION:?

A) WHICH ITEMS ARE IN LUNCH?

CLICK HERE

. Print "Hello World"

Description

This program prints the message Hello World on the screen.

Program


hello :-
    write('Hello World!').

Run


?- hello.

Output


Hello World!
true.

Explanation

hello is a predicate.
write() displays text on the screen.
:- means "is defined as".

2. Input Your Name and Print It

Description

This program accepts a user's name and prints a greeting.

Program


greet :-
    write('Enter your name: '),
    read(Name),
    write('Hello '),
    write(Name).

Run


?- greet.

Sample Input


john.

Output


Enter your name:
john.
Hello john
true.

Explanation

read(Name) reads input from the keyboard.
The entered value is stored in variable Name.
write(Name) displays the stored value.

3. Input Two Numbers and Display Them

Description

This program reads two numbers and displays them.

Program


display_numbers :-
    write('Enter first number: '),
    read(A),
    write('Enter second number: '),
    read(B),
    write('First Number = '),
    write(A),
    nl,
    write('Second Number = '),
    write(B).

Run


?- display_numbers.

Sample Input


15.
25.

Output


Enter first number:
15.
Enter second number:
25.
First Number = 15
Second Number = 25
true.

Explanation

A stores the first number.
B stores the second number.
nl prints a new line.

4. Input a Number and Print Its Square

Description

This program accepts a number and prints its square.

Program


square :-
    write('Enter a number: '),
    read(N),
    S is N * N,
    write('Square = '),
    write(S).

Run


?- square.

Sample Input

8.

Output


Enter a number:
8.
Square = 64
true.

Explanation

read(N) reads the number.
is evaluates arithmetic expressions.
S stores the square of N.

5. Input Age and Display Eligibility to Vote

Description

This program checks whether a person is eligible to vote.

Program


vote :-
    write('Enter your age: '),
    read(Age),
    Age >= 18,
    write('Eligible to vote.').

vote :-
    write('Enter your age: '),
    read(Age),
    Age < 18,
    write('Not eligible to vote.').

Run


?- vote.

Sample Input

20.

Output


Enter your age:
20.
Eligible to vote.
true.

Sample Input

15.

Output


Enter your age:
15.
Not eligible to vote.
true.

Explanation

>= checks if the age is 18 or more.
< checks if the age is less than 18.
Based on the condition, the appropriate message is printed.

Prolog Operators with Examples

Operators in Prolog are symbols used to perform arithmetic calculations, comparisons, logical operations, and term matching.

1. Arithmetic Operators

These operators perform mathematical calculations.

Operator	Meaning	Example	Result
`+`	Addition	`X is 10 + 5.`	`X = 15`
`-`	Subtraction	`X is 10 - 5.`	`X = 5`
`*`	Multiplication	`X is 10 * 5.`	`X = 50`
`/`	Division	`X is 10 / 5.`	`X = 2.0`
`//`	Integer Division	`X is 10 // 3.`	`X = 3`
`mod`	Remainder	`X is 10 mod 3.`	`X = 1`
`**`	Power	`X is 2 ** 3.`	`X = 8.0`

Example Program


calculate :-
    A is 20 + 10,
    B is 20 - 10,
    C is 20 * 10,
    D is 20 / 10,
    E is 20 // 3,
    F is 20 mod 3,
    G is 2 ** 4,
    write(A), nl,
    write(B), nl,
    write(C), nl,
    write(D), nl,
    write(E), nl,
    write(F), nl,
    write(G).

Output

2. Arithmetic Comparison Operators

These operators compare numeric values.

Operator	Meaning	Example	Result
`>`	Greater than	`10 > 5`	True
`<`	Less than	`5 < 10`	True
`>=`	Greater than or equal	`10 >= 10`	True
`=<`	Less than or equal	`5 =< 8`	True
`=:=`	Arithmetic equality	`5+5 =:= 10`	True
`=\=`	Arithmetic inequality	`10 =\= 5`	True

Example


compare :-
    X = 15,
    Y = 10,
    X > Y,
    write('X is greater than Y').

Output


X is greater than Y

3. Unification Operators

These operators compare or assign terms.

Operator	Meaning	Example
`=`	Unify two terms	`X = 10.`
`\=`	Not unifiable	`10 \= 20.`
`==`	Exactly identical	`10 == 10.`
`\==`	Not identical	`10 \== 20.`

Example


test :-
    X = apple,
    write(X).

Output


apple

4. Logical Operators

These operators combine conditions.

Operator	Meaning	Example
`,`	AND	`A > 5, A < 20`
`;`	OR	`A = 5 ; A = 10`
`\+`	NOT	`\+ (5 > 10)`

Example


check :-
    X = 15,
    X > 10,
    X < 20,
    write('Number is between 10 and 20').

Output


Number is between 10 and 20

5. Assignment Operator (`is`)

The is operator evaluates an arithmetic expression and assigns the result to a variable.

Syntax


Variable is Expression.

Example


square :-
    N = 6,
    S is N * N,
    write(S).

Output

6. Example Program Using Multiple Operators


demo :-
    write('Enter first number: '),
    read(A),
    write('Enter second number: '),
    read(B),

    Sum is A + B,
    Product is A * B,

    write('Sum = '),
    write(Sum), nl,

    write('Product = '),
    write(Product), nl,

    (A > B ->
        write('First number is greater')
    ;
        write('Second number is greater or equal')
    ).

Sample Run


?- demo.

Enter first number:
12.

Enter second number:
8.

Sum = 20
Product = 96
First number is greater

true.

Summary of Prolog Operators

Category	Operators
Arithmetic	`+`, `-`, ``, `/`, `//`, `mod`, `*`
Comparison	`>`, `<`, `>=`, `=<`, `=:=`, `=\=`
Unification	`=`, `\=`, `==`, `\==`
Logical	`,` (AND), `;` (OR), `\+` (NOT)
Assignment	`is`

IF-ELSE in Prolog

Unlike languages such as C, C++, or Java, Prolog does not have a traditional if-else statement. Instead, it uses the If-Then-Else operator (-> ;).

Syntax


(Condition ->
    Then_Part
;
    Else_Part
).

Meaning

Condition → Checks the condition.
-> → Means THEN.
; → Means ELSE.

Example 1: Check Eligible to Vote

Program


vote :-
    write('Enter your age: '),
    read(Age),
    (Age >= 18 ->
        write('Eligible to Vote')
    ;
        write('Not Eligible to Vote')
    ).

Run


?- vote.

Sample Input

20.

Output


Enter your age:
20.
Eligible to Vote
true.

Sample Input

15.

Output


Enter your age:
15.
Not Eligible to Vote
true.

Example 2: Find Larger Number

Program


largest :-
    write('Enter first number: '),
    read(A),

    write('Enter second number: '),
    read(B),

    (A > B ->
        write('Largest Number = '),
        write(A)
    ;
        write('Largest Number = '),
        write(B)
    ).

Sample Run


?- largest.

Enter first number:
10.

Enter second number:
25.

Largest Number = 25

true.

Example 3: Check Even or Odd

Program


evenodd :-
    write('Enter a number: '),
    read(N),

    (N mod 2 =:= 0 ->
        write('Even Number')
    ;
        write('Odd Number')
    ).

Sample Output


?- evenodd.

Enter a number:
18.

Even Number

true.

Example 4: Find Positive or Negative

Program


sign :-
    write('Enter a number: '),
    read(N),

    (N >= 0 ->
        write('Positive Number')
    ;
        write('Negative Number')
    ).

Output


?- sign.

Enter a number:
-8.

Negative Number

true.

Example 5: Pass or Fail

Program


result :-
    write('Enter marks: '),
    read(Marks),

    (Marks >= 40 ->
        write('Pass')
    ;
        write('Fail')
    ).

Output


?- result.

Enter marks:
65.

Pass

true.

Nested IF-ELSE Example (Grade Calculator)

Program


grade :-
    write('Enter marks: '),
    read(M),

    (M >= 90 ->
        write('Grade A')
    ;
        (M >= 75 ->
            write('Grade B')
        ;
            (M >= 50 ->
                write('Grade C')
            ;
                write('Fail')
            )
        )
    ).

Sample Run


?- grade.

Enter marks:
82.

Grade B

true.

General Syntax


predicate :-
    (Condition ->
        Statement1
    ;
        Statement2
    ).

Difference Between C and Prolog IF-ELSE

C/C++	Prolog
`if(condition)`	`(Condition -> ...)`
`else`	`;`
`{ }` block	Parentheses `( )`
Statement ends with `;`	Predicate ends with `.`

What is a List in Prolog?

A list is a collection of elements enclosed in square brackets [ ].

A list can contain numbers, atoms, variables, or even other lists.
Elements are separated by commas.

Syntax


[Element1, Element2, Element3, ...]

Examples


[1,2,3,4,5]

[apple, mango, orange]

[a,10,hello,25]

[]

Characteristics of a List

Ordered collection of elements.
Elements are enclosed within [ ].
Elements are separated by commas.
A list may contain duplicate values.
Lists can contain different data types.

Example


[10,20,30]


[apple,25,mango]

[]

Head and Tail of a List

A list consists of:

Head → First element
Tail → Remaining elements

Syntax


[Head|Tail]

Example


[10,20,30,40]

Head

Tail


[20,30,40]

Example Program


show :-
    L = [10,20,30,40],
    L = [H|T],
    write('Head = '),
    write(H), nl,
    write('Tail = '),
    write(T).

Run


?- show.

Output


Head = 10
Tail = [20,30,40]

true.

Empty List

An empty list contains no elements.

Syntax

[]

Example


empty :-
    L=[],
    write(L).

Output

[]

List Matching (Pattern Matching)

Prolog matches list elements using variables.

Example


match :-
    [A,B,C]=[100,200,300],
    write(A),nl,
    write(B),nl,
    write(C).

Output


100
200
300

Check Membership using member/2

The member/2 predicate checks whether an element exists in a list.

Syntax


member(Element,List)

Example


check :-
    member(30,[10,20,30,40]).

Run


?- check.

Output


true.

Another Example


?- member(mango,[apple,mango,banana]).

Output


true.

Append Two Lists

The append/3 predicate joins two lists.

Syntax


append(List1,List2,Result).

Example


join :-
    append([1,2,3],[4,5,6],L),
    write(L).

Output


[1,2,3,4,5,6]

Length of a List

The length/2 predicate counts the number of elements.

Example


size :-
    length([10,20,30,40,50],N),
    write(N).

Output

Reverse a List

The reverse/2 predicate reverses a list.

Example


rev :-
    reverse([10,20,30,40],R),
    write(R).

Output


[40,30,20,10]

Sort a List

The sort/2 predicate arranges elements in ascending order.

Example


sorting :-
    sort([5,2,8,1,6],L),
    write(L).

Output


[1,2,5,6,8]

Find Maximum Element


maximum :-
    max_list([15,28,9,45,30],M),
    write(M).

Output

Find Minimum Element


minimum :-
    min_list([15,28,9,45,30],M),
    write(M).

Output

Sum of List Elements


sum :-
    sum_list([10,20,30,40],S),
    write(S).

Output

Nested List

Lists can contain other lists.

Example


[1,2,[3,4],5]

Another Example


[[a,b],[c,d],[e,f]]

Access Head and Tail


headtail :-
    [H|T]=[apple,mango,banana,orange],
    write(H),nl,
    write(T).

Output


apple
[mango,banana,orange]

Generate List Members


show :-
    member(X,[10,20,30]),
    write(X),nl,
    fail.
show.

Output


10
20
30
true.

Common Built-in List Predicates

Predicate	Description	Example
`member/2`	Checks whether an element exists	`member(5,[1,2,5])`
`append/3`	Joins two lists	`append([1],[2],L)`
`length/2`	Counts elements	`length([1,2,3],N)`
`reverse/2`	Reverses a list	`reverse([1,2],R)`
`sort/2`	Sorts elements	`sort([4,2,1],L)`
`max_list/2`	Finds the largest element	`max_list([2,5,3],M)`
`min_list/2`	Finds the smallest element	`min_list([2,5,3],M)`
`sum_list/2`	Calculates the sum of elements	`sum_list([1,2,3],S)`

Advantages of Lists

Easy to store multiple values.
Dynamic size (can grow or shrink).
Supports recursion efficiently.
Useful for searching and pattern matching.
Widely used in Artificial Intelligence and symbolic programming.

What is Cut (`!`)?

The Cut operator (!) is a special control operator in Prolog.

It is used to stop backtracking and prevent Prolog from searching for alternative solutions after the cut is reached.

Definition

The Cut (!) is a control operator that commits Prolog to the choices made before it and prevents further backtracking beyond that point.

Syntax


Predicate :-
    Goal1,
    Goal2,
    !,
    Goal3.

Why Do We Use Cut?

Improves program efficiency.
Stops unnecessary backtracking.
Makes the program execute faster.
Selects only one solution.
Prevents Prolog from trying other rules.

How Cut Works

Without Cut


Goal
 │
 ▼
Rule 1
 │
 ▼
Failure
 │
 ▼
Backtracking
 │
 ▼
Rule 2

With Cut


Goal
 │
 ▼
Rule 1
 │
 ▼
 !
 │
 ▼
No Backtracking
 │
 ▼
Program Ends

Example 1: Simple Cut

Program


largest(X,Y,X) :-
    X >= Y,
    !.

largest(_,Y,Y).

Run


?- largest(20,15,R).

Output


R = 20

Explanation

20 >= 15 is true.
Prolog reaches !.
Backtracking stops.
The second rule is ignored.

Example 2: Without Cut


largest(X,Y,X) :-
    X >= Y.

largest(_,Y,Y).

Run


?- largest(20,15,R).

Output


R = 20 ;
R = 15.

Explanation

Since there is no Cut, Prolog also tries the second rule during backtracking.

Example 3: Check Positive Number


positive(X) :-
    X > 0,
    !,
    write('Positive Number').

positive(_) :-
    write('Not Positive').

Run


?- positive(15).

Output


Positive Number
true.

Another Run


?- positive(-5).

Output


Not Positive
true.

Example 4: Maximum of Two Numbers


max(A,B,A) :-
    A >= B,
    !.

max(_,B,B).

Run


?- max(50,20,R).

Output


R = 50

Example 5: Grade Calculator


grade(Marks) :-
    Marks >= 90,
    !,
    write('Grade A').

grade(Marks) :-
    Marks >= 75,
    !,
    write('Grade B').

grade(Marks) :-
    Marks >= 50,
    !,
    write('Grade C').

grade(_) :-
    write('Fail').

Run


?- grade(82).

Output


Grade B
true.

Example 6: Voting Eligibility


vote(Age) :-
    Age >= 18,
    !,
    write('Eligible to Vote').

vote(_) :-
    write('Not Eligible').

Run


?- vote(20).

Output


Eligible to Vote

Example 7: Even or Odd


evenodd(N) :-
    N mod 2 =:= 0,
    !,
    write('Even Number').

evenodd(_) :-
    write('Odd Number').

Run


?- evenodd(12).

Output


Even Number

Cut with If-Then-Else


largest :-
    write('Enter First Number: '),
    read(A),

    write('Enter Second Number: '),
    read(B),

    (A > B ->
        write('Largest = '),
        write(A)
    ;
        write('Largest = '),
        write(B)
    ).

This example uses If-Then-Else (-> ;) and does not require Cut, because the conditional already commits to one branch.

Types of Cut

1. Green Cut

A Green Cut improves efficiency without changing the logical meaning of the program.

Example


max(X,Y,X) :-
    X >= Y,
    !.

max(_,Y,Y).

Purpose: Prevents unnecessary backtracking while preserving correct results.

2. Red Cut

A Red Cut changes the logical behavior of the program. Using or removing it may change the answers produced.

Example


grade(Marks) :-
    Marks >= 40,
    !,
    write('Pass').

grade(_) :-
    write('Fail').

Here, the cut commits to the first matching rule, affecting how later rules are considered.

Advantages of Cut

Stops unnecessary backtracking.
Makes execution faster.
Improves program efficiency.
Reduces memory usage.
Produces a single desired solution.
Simplifies control flow in some programs.

Disadvantages of Cut

Can make programs harder to understand.
May change the logical meaning if used incorrectly.
Makes debugging more difficult.
Overuse can reduce program readability.

Difference Between Cut and If-Else

Cut (`!`)	If-Then-Else (`-> ;`)
Stops backtracking	Selects one branch based on a condition
Used for execution control	Used for conditional decisions
Can affect later rule selection	Does not rely on multiple clauses
May improve efficiency	Improves readability for conditions

Summary

Symbol	Meaning
`!`	Cut operator
Purpose	Stops backtracking
Benefit	Improves efficiency and selects a single solution
Types	Green Cut, Red Cut
Main Use	Control execution and avoid unnecessary alternative solutions

SEM 1	SEM 2	SEM 3
SEM 4	SEM 5	SEM 6

SEM 1	SEM 2	SEM 3
SEM 4	SEM 5	SEM 6

SEM 1	SEM 2	SEM 3
SEM 4	SEM 5	SEM 6

CLASS-4	CLASS-5	CLASS-6
CLASS-7	CLASS-8	CLASS-9
CLASS10	CLASS11 application	CLASS12 application
CLASS11 science	CLASS12 science

C	C++	CORE JAVA	SQL	PYTHON
MS OFFICE	HTML	VISUAL BASIC	advanced java	8085
PROLOG	ASSEMBLY LANGUAGE	JAVA SCRIPT	SHELL PROGRAMMING	R
DIGITAL ELECTRONICS	COMPUTER ARCHITECTURE	DATA STRUCTURE	OPERATING SYSTEM	GRAPH THEORY
DISCRETE MATHEMATICS	NUMERICAL ALGORITHM	AUTOMATA	MICROPROCESSOR	NETWORKING
GRAPHICS	SOFTWARE ENGINEERING	DATABSE	ANALYSIS OF ALGORITHM	IMAGE PROCESSING
ARTIFICIAL INTELLIGENCE	BIG DATA	CLOUD COMPUTING	DATA MINING	INTERNET TECHNOLOGY

CU BSC computer science old syllabus	WBSU BSC computer science old syllabus
CU cbcs BSC computer science HONOURS syllabus 2018	WBSU cbcs BSc computer science HONOURS syllabus 2018
CU cbcs BSC computer science GENERAL syllabus 2018	WBSU cbcs BSC computer science GENERAL syllabus 2018

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Sunday, May 16, 2021

PROLOG PROGRAM LIST:::

. Print "Hello World"

Description

Program

Run

Output

Explanation

2. Input Your Name and Print It

Description

Program

Run

Sample Input

Output

Explanation

3. Input Two Numbers and Display Them

Description

Program

Run

Sample Input

Output

Explanation

4. Input a Number and Print Its Square

Description

Program

Run

Sample Input

Output

Explanation

5. Input Age and Display Eligibility to Vote

Description

Program

Run

Sample Input

Output

Sample Input

Output

Explanation

Prolog Operators with Examples

1. Arithmetic Operators

Example Program

Output

2. Arithmetic Comparison Operators

Example

Output

3. Unification Operators

Example

Output

4. Logical Operators

Example

Output

5. Assignment Operator (is)

Syntax

Example

Output

6. Example Program Using Multiple Operators

Sample Run

Summary of Prolog Operators

IF-ELSE in Prolog

Syntax

Meaning

Example 1: Check Eligible to Vote

Program

Run

Sample Input

Output

Sample Input

Output

Example 2: Find Larger Number

Program

Sample Run

Example 3: Check Even or Odd

Program

Sample Output

Example 4: Find Positive or Negative

Program

Output

Example 5: Pass or Fail

Program

5. Assignment Operator (`is`)

What is Cut (`!`)?