Programming of Arithmetic Operators and Predicates

Prolog is used to develop Information Systems other than the Expert Systems. Therefore, it supports the arithmetic operators like procedural programming languages, such as C, C++ and JAVA. Common arithmetic operators are as follows:

Arithmetic Operator	Meaning	Example
+	Addition	1+2=3
-	Subtraction	12-7=5
*	Multiplication	2*3=6
/	Floating Point Division	8/3=2.66
//	Integer Division	8/3=2
%	Mod (Remainder)	5%2= 1
**	Power	2**2=4

Relation operators are called as arithmetic predicates using Prolog. Common arithmetic predicates are as follows:

Expression	Symbols	Example
Evaluate	is	X is 2+2. Result: X= 4 Yes
Equal To	= : =	4-1 = : = 1+2. Result: Yes
Greater Than	>	X is 2+2, X > 5. Result: 4 Yes
Greater Than and Equal To	>=	X is 2+3, X >= 5. Result: 5 Yes
Less Than	<	X is 1+2, X < 4. Result: 3 Yes
Less Than and Equal To	=<	X is 2+2, X =< 4. Result: 4 Yes
Comparison operators to assign value	=	X+2 = 1+Y. Result: X = 1 , Y = 2 Yes

Example #1

Develop a program using Prolog to add two numbers based on the user input:

/*Declare Rule To Add Two Numbers*/

add(Sum,Num1,Num2):-

Sum is Num1+Num2

Example #2

Develop a program using Prolog to calculate area of rectangle based on the user input:

/*Declare Rule To Compute Area*/

compute(Area,Length,Width):-

write(‘Area of Rectangle is ‘),

Area is Length*Width.

Example #3

Develop a program using Prolog to calculate area, diameter and circumference of circle. Formulas are shown below to calculate area, diameter and circumference:

Area of circle is PI*Radius*Radius.

Diameter of circle is 2*Radius.

Circumference of circle is 2*PI*Radius.

/*Declare Rule To Compute Area, Diameter and Circumference*/

compute(Area,Dia,Circum, Radius):-

Area is (3.1416*Radius**2),

Dia is (2*Radius),

Circum is (2*3.1416*Radius).

Programming to use Append Using Structures

Structure [Thing | Room] is indicating that variable ‘Thing’ is bounded to the first element of list where as variable ‘Room’ is bounded to remaining elements of list. Syntax of a query is as follows:

? [Thing | Room] = [apple, knife, crackers]

Thing = apple

Room = [knife, crackers]

Predicate used to construct or segregate the lists is called ‘Append’. Syntax to use append predicate is as follows:

? append ([apple, banana],[knife, crackers],Things).

Things = [apple, banana, knife, crackers]

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