Transcript Scheme - Computer Science & Engineering

λ
Scheme
JD White III
Kevin Sweeney
Josh Amick
Jonathan Eitel
About
Scheme was invented by Guy Lewis
Steele Jr. and Gerald Jay Sussman in the
1970’s
Dialect of Lisp
Designed for clear and simple semantics
One of the first languages to incorporate
first class procedures
Introduced concept of exact and inexact
numbers
About (cont.)
Supports multiple programming paradigms
Best known for support of functional
programming
Follows a minimalist philosophy;
everything provided by libraries
Widely used by schools for introductory
programming courses: Stanford, MIT, etc.
Concepts
Scheme has lexical scoping and uniform
evaluation rules
All data types are equal
There are seven kinds of expressions:
Constant, Variable reference, Procedure
creation, Procedure application,
Conditional, Assignment, and Sequence.
Types
Numbers

1, 2, 3.1459,
Strings

“Take home exam, please”
Char’s

#\a, #\b
Bools

#t
#f
Syntax
Compute expressions from the inside out
No operator precedence rules
Uses fully nested and parenthesized notation
Conditionals:

(if test then-expr else-expr)
Nested Conditionals:

(cond (test1 expr1 ...) (test2 expr2 ...) ... (else
exprn))
Sample Program: Factorial
(define (fact n)
(if (< n 2)
1
(* n (fact (- n 1))))))
(defun fact (n)
(if (< n 2)
1
(* n (fact (1- n)))))
Prefix vs. Infix
Prefix: (* 2 (+ 1 2))


Parenthesis are a must
(+ 2 4 6 8) = 20
Infix: 2 * ( 1 + 2)


Parenthesis used to override execution order
If the more than 2 arguments, then the
operator must be repeated
These have the same execution order
Scheme vs. C
Scheme
(factorial 3)
(+ 1 2)
(+ 1 2 3)
(< low X high)
( * (+ 1 2) 3)
C
Factorial(9)
1+2
1+2+3
(low < X) && (hi < X)
(1 + 2) * 3
Sources
Wikipedia:
http://en.wikipedia.org/wiki/Scheme_programming_language
MIT: http://www-swiss.ai.mit.edu/projects/scheme/
University of Washington:
http://www.cs.washington.edu/education/courses/341/99su/lectures/
scheme/ppframe.htm
University of Michigan-Dearborn:
http://www.engin.umd.umich.edu/CIS/course.des/cis400/scheme/sch
eme.html