Growing Schemes

Twenty Years of Scheme Requests for Implementation

Arthur A. Gleckler
SRFI Editor

How do we grow the language?

Outline

☐ Purpose of the SRFI process
☐ How you can participate
☐ How SRFIs have helped Scheme evolve
☐ Future

SRFI Motivation (I)

You're writing a Scheme program. You might need:
- a lightweight testing framework
- an extensive list-, string-, or vector-manipulation library
- a purely functional mapping data structure
- operating-system facilities like:
  - multithreading
  - socket-based networking
  - detecting the OS version
  - compiling programs to executables
- better syntax for handling multiple return values
- some other language feaure or library

SRFI Motivation (II)

You're writing or maintaining a Scheme implementation.
- Want to add support for new features.
- Need a sample implementation.

SRFI Motivation (III)

You want some features added to Scheme.
- implementations
- standards

What are the SRFIs?

A process for extending Scheme
Parallel effort to R⁶RS and R⁷RS-small and -large
163 detailed proposals so far
Requests, not requirements
Twenty years old this month (26 Sep 1998)

SRFI vs. RⁿRS

Simpler, much shorter process.
Consensus not required.
Time from proposal to completion much shorter.
Not requirements. Only requests.
Driven by contributors and reviewers.

SRFI Survey

SRFIs 0-9

0	final	Feature-based conditional expansion construct
1	final	List Library
2	final	AND-LET: an AND with local bindings, a guarded LET special form
3	withdrawn	List-Set Library
4	final	Homogeneous numeric vector datatypes
5	final	A compatible let form with signatures and rest arguments
6	final	Basic String Ports
7	final	Feature-based program configuration language
8	final	receive: Binding to multiple values
9	final	Defining Record Types

SRFIs 10-19

10	final	#, external form
11	final	Syntax for receiving multiple values
12	withdrawn	Exception Handling
13	final	String Libraries
14	final	Character-set Library
15	withdrawn	Syntax for dynamic scoping
16	final	Syntax for procedures of variable arity
17	final	Generalized set!
18	final	Multithreading support
19	final	Time Data Types and Procedures

SRFIs 20-29

20	withdrawn	Simple object system
21	final	Real-time multithreading support
22	final	Running Scheme Scripts on Unix
23	final	Error reporting mechanism
24	withdrawn	Define-syntax in local lexical scopes
25	final	Multi-dimensional Array Primitives
26	final	Notation for Specializing Parameters without Currying
27	final	Sources of Random Bits
28	final	Basic Format Strings
29	final	Localization

SRFIs 30-39

30	final	Nested Multi-line Comments
31	final	A special form `rec' for recursive evaluation
32	withdrawn	Sort Libraries
33	withdrawn	Integer Bitwise-operation Library
34	final	Exception Handling for Programs
35	final	Conditions
36	final	I/O Conditions
37	final	args-fold: a program argument processor
38	final	External Representation for Data With Shared Structure
39	final	Parameter objects

SRFIs 40-49

40	withdrawn	A Library of Streams
41	final	Streams
42	final	Eager Comprehensions
43	final	Vector library
44	final	Collections
45	final	Primitives for Expressing Iterative Lazy Algorithms
46	final	Basic Syntax-rules Extensions
47	final	Array
48	final	Intermediate Format Strings
49	final	Indentation-sensitive syntax

SRFIs 50-59

50	withdrawn	Mixing Scheme and C
51	final	Handling rest list
52	withdrawn	Permitting and Supporting Extended Character Sets
53	withdrawn	Syntactic computations with computation-rules
54	final	Formatting
55	final	require-extension
56	withdrawn	Binary I/O
57	final	Records
58	final	Array Notation
59	final	Vicinity

SRFIs 60-69

60	final	Integers as Bits
61	final	A more general cond clause
62	final	S-expression comments
63	final	Homogeneous and Heterogeneous Arrays
64	final	A Scheme API for test suites
65	withdrawn	define-immutable: A Syntax to Define Identifiers With Immutable Values
66	final	Octet Vectors
67	final	Compare Procedures
68	withdrawn	Comprehensive I/O
69	final	Basic hash tables

SRFIs 70-79

70	final	Numbers
71	final	Extended LET-syntax for multiple values
72	final	Hygienic macros
73	withdrawn	Exact Infinities
74	final	Octet-Addressed Binary Blocks
75	withdrawn	R⁶RS Unicode data
76	withdrawn	R⁶RS Records
77	withdrawn	Preliminary Proposal for R⁶RS Arithmetic
78	final	Lightweight testing
79	withdrawn	Primitive I/O

SRFIs 80-89

80	withdrawn	Stream I/O
81	withdrawn	Port I/O
82	withdrawn	Stream Ports
83	withdrawn	R⁶RS Library Syntax
84	withdrawn	Universal Identifiers
85	withdrawn	Recursive Equivalence Predicates
86	final	MU and NU simulating VALUES & CALL-WITH-VALUES, and their related LET-syntax
87	final	=> in case clauses
88	final	Keyword objects
89	final	Optional positional and named parameters

SRFIs 90-99

90	final	Extensible hash table constructor
91	withdrawn	Extended ports
92	withdrawn	ALAMBDA and ALAMBDA*
93	withdrawn	R⁶RS Syntax-Case Macros
94	final	Type-Restricted Numerical Functions
95	final	Sorting and Merging
96	final	SLIB Prerequisites
97	final	SRFI Libraries
98	final	An interface to access environment variables
99	final	ERR⁵RS Records

SRFIs 100-109

100	final	define-lambda-object
101	final	Purely Functional Random-Access Pairs and Lists
102	withdrawn	Procedure Arity Inspection
103	withdrawn	Library Files
104	withdrawn	Library Files Utilities
105	final	Curly-infix-expressions
106	final	Basic socket interface
107	final	XML reader syntax
108	final	Named quasi-literal constructors
109	final	Extended string quasi-literals

SRFIs 110-119

110	final	Sweet-expressions (t-expressions)
111	final	Boxes
112	final	Environment Inquiry
113	final	Sets and bags
114	withdrawn	Comparators
115	final	Scheme Regular Expressions
116	final	Immutable List Library
117	final	Mutable Queues
118	final	Simple adjustable-size strings
119	final	wisp: simpler indentation-sensitive scheme

SRFIs 120-129

120	final	Timer APIs
121	final	Generators
122	final	Nonempty Intervals and Generalized Arrays
123	final	Generic accessor and modifier operators
124	final	Ephemerons
125	final	Intermediate hash tables
126	final	R⁶RS-based hashtables
127	final	Lazy Sequences
128	final	Comparators (reduced)
129	final	Titlecase procedures

SRFIs 130-139

130	final	Cursor-based string library
131	final	ERR⁵RS Record Syntax (reduced)
132	final	Sort Libraries
133	final	Vector Library (R⁷RS-compatible)
134	final	Immutable Deques
135	final	Immutable Texts
136	final	Extensible record types
137	final	Minimal Unique Types
138	final	Compiling Scheme programs to executables
139	final	Syntax parameters

SRFIs 140-149

140	final	Immutable Strings
141	final	Integer division
142	withdrawn	Bitwise Operations
143	final	Fixnums
144	final	Flonums
145	final	Assumptions
146	final	Mappings
147	final	Custom macro transformers
148	final	Eager syntax-rules
149	final	Basic Syntax-rules Template Extensions

SRFIs 150-159

150	final	Hygienic ERR⁵RS Record Syntax (reduced)
151	final	Bitwise Operations
152	final	String Library (reduced)
153	withdrawn	Ordered Sets
154	final	First-class dynamic extents
155	final	Promises
156	final	Syntactic combiners for binary predicates
157	final	Continuation marks
158	final	Generators and Accumulators
159	final	Combinator Formatting

SRFIs 160-162

160	draft	Homogeneous numeric vector libraries
161	draft	Unifiable Boxes
162	draft	Comparators sublibrary

Talk progress

☑ Purpose of the SRFI process
☐ How you can participate
☐ How SRFIs have helped Scheme evolve
☐ Future

SRFI Process > Steps (I)

Prepare a proposal (a SRFI).
- design document (based on simple template)
- sample implementation
- tests
Send proposal to srfi-editors@srfi.schemers.org.
Editor publishes proposal on srfi.schemers.org.
- public announcement on srfi-announce@srfi.schemers.org

SRFI Process > Steps (II)

Discuss proposal publicly.
- Each SRFI has its own public mailing list.
- 60-90 days.
Revise proposal.
- Editor publishes and announces new drafts.
Finalize proposal (or withdraw it).
Ask implementers to support proposal.

SRFI Process > States

Once announced, SRFIs are public forever.
Discussion is archived publicly.
Document and code are kept under public version control.

Talk progress

☑ Purpose of the SRFI process
☑ How you can participate
☐ How SRFIs have helped Scheme evolve
☐ Future

SRFI History

Started in 1998 (when R⁵RS was published).
163 SRFIs so far
- 3 draft
- 126 final
- 34 withdrawn

SRFI History > Cumulative SRFIs

SRFI History > Relation to RⁿRS

SRFI History > Relation to R⁶RS

Organized around SRFI process (draft, then withdraw).
Incorporated subset of SRFI 1.
Largely incorporated SRFI 11, 33, 34, 60, 74, 75, 76, 77, 83, and 93.

SRFI History > Relation to R⁷RS

Small
- Influenced by SRFIs 0, 1, 4, 6, 9, 11, 13, 16, 30, 34, 39, 43, 45, 46, 62 and 87.
Large
- Organized around SRFI process.
- Editor John Cowan has co-authored SRFIs 111, 112, 113, 114, 116, 117, 121, 124, 125, 127, 128, 129, 130, 131, 132, 133, 134, 137, 141, 142, 143, 144, 150, 151, 152, 153, 158, 160, and 162.

SRFI History > Survey of implementations

SRFI History > Survey > Counts

SRFI History > Survey > Matrix

X axis: SRFI number
Y axis: various Scheme implementations

Talk progress

☑ Purpose of the SRFI process
☑ How you can participate
☑ How SRFIs have helped Scheme evolve
☐ Future

Talk progress

☑ Purpose of the SRFI process
☑ How you can participate
☑ How SRFIs have helped Scheme evolve
☐ Future

SRFI Future

Duration and deadlines
Semantic mark-up
Search engine for SRFI bindings
- Ciprian Dorin Craciun's proposed format (Github)
  - R7RS first
- gwatt (IRC) proposed something like Haskell's Hoogle and Hayoo

Conclusion

SRFI: formal process for coordinating libraries and other additions to the Scheme language between implementations
Widely used.
Pleasant community (716 unique email addresses).
Please contribute.
- SRFIs
- discussion
- etc. (e.g. search index, repo mirrors)

Slides and Paper

Extra slides

The Reports

RS	Scheme: An Interpreter for Extended Lambda Calculus (AIM 349)	1975
R²RS	The Revised Report on Scheme, A Dialect of Lisp (AIM 452)	1978
R³RS	The Revised Revised Report on Scheme, or An UnCommon Lisp (AIM 848)	1985
IEEE-1178	IEEE Standard for the Scheme Programming Language	1990, 2008
R⁴RS	Revised⁴ Report on the Algorithmic Language Scheme	1991
R⁵RS	Revised⁵ Report on the Algorithmic Language Scheme	1998
R⁶RS	Revised⁶ Report on the Algorithmic Language Scheme	2007
R⁷RS small	Revised⁷ Report on the Algorithmic Language Scheme	2013
R⁷RS large	Revised⁷ Report on the Algorithmic Language Scheme	in progress

Snow (or Snow Fort)

… a place to share Scheme programs, libraries and data
independent of SRFI
automatic installation of packages
by Alex Shinn (and Marc Feeley)
- editor of R⁷RS-small
- author of Chibi-Scheme

Diagrams > SRFI Home

SRFI home

SRFI History > Editors

Eight editors since 1998.
- Dave Mason
- David Rush
- David Van Horn
- Donovan Kolbly
- Francisco Solsona
- Mike Sperber
- Shriram Krishnamurthi
- me (starting July, 2015)
Four served for a decade or more.

SRFI History > Recent improvements

new web host for srfi.schemers.org: Linode.com
new email host: Simplelists.com
source control
- CVS ⇒ Git
- Split single CVS repo into a separate Git repo for each SRFI.
- CVS repo was private.
- Git repos are public.
  - Hosted on Github.com.
Support pull requests as well as patches and raw updates.
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