This document summarizes some of the key changes introduced in the R7RS revision of the Scheme programming language standard. These include: 1) The introduction of define-record-type, which provides built-in support for record types and objects, giving Scheme aspects of object-oriented programming. 2) Standardization of the library system notation, allowing libraries to be loaded consistently across implementations using import. 3) Inclusion of exceptions handling from SRFI-34, using with-exception-handler to catch and handle exceptions.

1. .
.
What Does R7RS
Change Programming in Scheme?
Kazuhiro Hishinuma (Twitter: @kazh98)
Department of Computer Science, Meiji University
1-1-1 Higashimita, Tama-ku, Kawasaki-shi, Kanagawa, 214-8571 Japan
K. Hishinuma
What Does R7RS Change Programming in Scheme?

2. . What is the Schemers’ Soul?
Snap out of it, Schemers!
K. Hishinuma
What Does R7RS Change Programming in Scheme?

3. . What is the Schemers’ Soul?
Snap out of it, Schemers!
Scheme is the simplest,
the smallest, and
the most powerful language!
K. Hishinuma
What Does R7RS Change Programming in Scheme?

4. . What is the Programmers’ Utopia?
And..., join us,
all lispers and programmers!
K. Hishinuma
What Does R7RS Change Programming in Scheme?

5. . What is the Programmers’ Utopia?
And..., join us,
all lispers and programmers!
Now, the most ideal language
is going to be born!
K. Hishinuma
What Does R7RS Change Programming in Scheme?

6. . Congratulation!
1
http://lists.scheme-reports.org/pipermail/
scheme-reports/2013-November/003832.html
K. Hishinuma
What Does R7RS Change Programming in Scheme?

7. . Congratulation!
R7RS-small draft
ratified by Steering Committee!! 1
1
http://lists.scheme-reports.org/pipermail/
scheme-reports/2013-November/003832.html
K. Hishinuma
What Does R7RS Change Programming in Scheme?

8. R7RS says ...
.
“Scheme demonstrates that
K. Hishinuma
What Does R7RS Change Programming in Scheme?

9. R7RS says ...
.
“Scheme demonstrates that
a very small number of rules
for forming expressions,
K. Hishinuma
What Does R7RS Change Programming in Scheme?

10. R7RS says ...
.
“Scheme demonstrates that
a very small number of rules
for forming expressions, with no restrictions
K. Hishinuma
What Does R7RS Change Programming in Scheme?

11. R7RS says ...
.
“Scheme demonstrates that
a very small number of rules
for forming expressions, with no restrictions
on how they are composed.”
K. Hishinuma
What Does R7RS Change Programming in Scheme?

12. . So, today.
Let us think what is
The Genuine Programming
In R7RS Scheme.
K. Hishinuma
What Does R7RS Change Programming in Scheme?

13. Three Hot Changes1
.
Record-type (cf. pp.27–)
Library System (cf. pp.28–)
Exceptions (cf. pp.54–)
1
from R5 RS
K. Hishinuma
What Does R7RS Change Programming in Scheme?

14. Three Hot Changes1
.
Record-type (cf. pp.27–)
Library System (cf. pp.28–)
Exceptions (cf. pp.54–)
1
from R5 RS
K. Hishinuma
What Does R7RS Change Programming in Scheme?

15. . Record-type
(define-record-type name
(cname f1 f2 ...)
pred?
(f1 ref-f1 set-f1 !)
(f2 ref-f2 set-f2 !)
...)
name Name of the record to be defined
pred? Name of the predicatior for this record
f1 , f2 , ... Names of the fields of this record
K. Hishinuma
What Does R7RS Change Programming in Scheme?

16. . e.g. CONS, CAR, CDR
Existing method:
(define (cons a b)
(lambda (s) (s a b)))
(define (car c)
(c (lambda (a b) a)))
(define (cdr c)
(c (lambda (a b) b)))
(define c (cons ’a ’b))
(car c) ;= ’a
(cdr c) ;= ’b
K. Hishinuma
(pair? c) ;= ?!
(set-car! c ’d)
(car c) ;= ?!
What Does R7RS Change Programming in Scheme?

17. . e.g. CONS, CAR, CDR
Proposed method:
(define-record-type pair
(cons a b)
pair?
(a car set-car!)
(b cdr set-cdr!))
(define c (cons ’a ’b))
(car c) ;= ’a
(cdr c) ;= ’b
K. Hishinuma
(pair? c) ;= #t
(set-car! c ’d)
(car c) ;= ’d
What Does R7RS Change Programming in Scheme?

18. . define-record-type give Scheme ...
K. Hishinuma
What Does R7RS Change Programming in Scheme?

19. . define-record-type give Scheme ...
The seed of
Object-Oriented Programming!
K. Hishinuma
What Does R7RS Change Programming in Scheme?

20. Three Hot Changes1
.
Record-type (cf. pp.27–)
Library System (cf. pp.28–)
Exceptions (cf. pp.54–)
1
from R5 RS
K. Hishinuma
What Does R7RS Change Programming in Scheme?

21. . Good news!
Notation for library system
is standardized!!
K. Hishinuma
What Does R7RS Change Programming in Scheme?

22. . How to load SRFI-1
Gauche (use srfi-1)
Guile (srfi srfi-1)
Racket (require srfi/1)
K. Hishinuma
What Does R7RS Change Programming in Scheme?

23. . How to load SRFI-1
Gauche (use srfi-1)
Guile (srfi srfi-1)
Racket (require srfi/1)
R7RS (import (srfi 1))
K. Hishinuma
What Does R7RS Change Programming in Scheme?

24. . How to make a library
(define-library (name ...)
(export ep ...)
(import (scheme base) ...)
(begin
(define (p1 args ...)
...) ...))
name Name of the library
ep ... List of names to be exported
K. Hishinuma
What Does R7RS Change Programming in Scheme?

25. Three Hot Changes1
.
Record-type (cf. pp.27–)
Library System (cf. pp.28–)
Exceptions (cf. pp.54–)
K. Hishinuma
What Does R7RS Change Programming in Scheme?

26. . What’s this?
SRFI-34 is included
in R7RS!
K. Hishinuma
What Does R7RS Change Programming in Scheme?

27. . with-exception-handler
e.g.
(with-exception-handler
(lambda (e) Handler for Exception e)
(lambda () Procedure which may raise exception))
(error ”This is an error message.”)
K. Hishinuma
What Does R7RS Change Programming in Scheme?

28. . Other Changes
K. Hishinuma
What Does R7RS Change Programming in Scheme?

29. . Other Changes
Case sensitivity is now the default in
symbols and character names.
K. Hishinuma
What Does R7RS Change Programming in Scheme?

30. . Other Changes
Case sensitivity is now the default in
symbols and character names.
Case-lambda (cf. pp.21–)
K. Hishinuma
What Does R7RS Change Programming in Scheme?

31. . Other Changes
Case sensitivity is now the default in
symbols and character names.
Case-lambda (cf. pp.21–)
The call-with-current-continuation
procedure now has the synonym call/cc.
K. Hishinuma
What Does R7RS Change Programming in Scheme?

32. Think in Scheme,
write in Scheme,
and show your Scheme!
Thanks for your listening.
K. Hishinuma
What Does R7RS Change Programming in Scheme?

33. . References
[1] J. Cowan: R7RS-small draft ratified by Steering Committee.
The public mailing lists on lists.scheme-reports.org, 2013.
http://lists.scheme-reports.org/pipermail/
scheme-reports/2013-November/003832.html
[2] A. Shinn, J. Cowan, and A. Gleckler: Revised7 Report on the
Algorithmic Language Scheme. Steering Committee, Scheme
Working Groups, 2013. http://trac.sacrideo.us/wg/
[3] Y. Kurosaki, and K. Hishinuma: Meiji Scheme Shell improved by
MOL. Meiji Scheme Project, Mathematical Optimization
Laboratory, Meiji University. https://github.com/meshmol/mesh
[4] K. Sasagawa: Normal Scheme. Scheme, 2013.
http://homepage1.nifty.com/~skz/Scheme/normal.html
K. Hishinuma
What Does R7RS Change Programming in Scheme?