Chapter 15
Functional Programming Languages
(Scheme Examples)
Dr. Muhammad Shafique
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Chapter 15 Functional Programming
Languages
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Introduction to Functional
Programming using Scheme
(http://htdp.org)
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Getting the Software – Installation and Related Issues
• Download the programming environment from http://drscheme.org
• Dr Scheme supports several variants of the Scheme programming
language.
• To begin with (derived from http:// htdp.org), we use “Beginning
Student Scheme”).
• You can select the language by:
• Language  Choose Language  Beginning Student
Scheme.
• Click “Run” or “Execute” for your changes to take
effect.
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Dr. Scheme
• The programming environment
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Part 2
Scheme Examples
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Example 1
• Develop a Scheme function to compute the factorial of a
given number
(define (factorial n)
(if
(< n 1)
1
(* n (factorial (- n 1)))
)
)
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Example 1
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Example 2
• Write a scheme function that computes the sum of all
elements of a given list.
(define evens ‘(0 2 4 6 8))
(define (sum alist)
(if
(null? alist) 0
(+ (car alist) (sum (cdr alist)))
)
)
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Example 2
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Example 3
• Write a scheme function to find the length (number of
elements) of a given list.
(define (length alist)
(if
(null? alist) 0
(+ 1 (length (cdr alist)))
)
)
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Example 3
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Example 4
• Develop a Scheme function that takes two arguments: a
function and a list. The function produces a new list which is
the result of applying the given argument function on the
elements of the given list.
(define (mapcar fun alist)
(if
(null? Alist) ‘()
(cons (fun (car alist) (mapcar fun (cdr alist)))
)
)
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Example 5
• Using the function defined in example 4 write a Scheme
program to compute the square of each element of a given list
(define evens ‘(0 2 4 6 8))
(define (square x (* x x))
(define (mapcar fun alist)
(if
(null? Alist) ‘()
(cons (fun (car alist)) (mapcar fun (cdr alist)))
)
)
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Example 5
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