Conference turris::languages

82.0. "B Language" by TRIVIA::STANSBURY (Jack) Sat Feb 01 1986 10:44

From the USENET - a description of an interactive programming language and 
environment called B:


Newsgroups: net.lang,net.micro.pc
Path: decwrl!pyramid!ut-sally!seismo!mcvax!boring!steven
Subject: B for the IBM PC and compatibles under MS-DOS
Posted: 29 Jan 86 14:48:45 GMT
Organization: CWI, Amsterdam
Xref: decwrl net.lang:2040 net.micro.pc:6719
Apparently-To: rnews@mcvax
 
(This B is unrelated to the predecessor of C: B is a working title.
The language will get its final name, ABC, when the language is frozen.)
 
Summary
There is now a first implementation of B available for the IBM PC and
compatibles under MS-DOS, alongside the existing implementation for Unix. It
is available for the cost of the media: $35 US, or Dfl. 100. Details of the
implementation and an order form are at the end of this article.
 
What is B? 
B is a new interactive programming language and environment that is as
simple as Basic to learn, offers the structure of C and Pascal, but thanks
to its high-level data-types is very powerful and convenient to use.
 
DATA-TYPES
It has 2 basic data-types: numbers and texts (=strings), and 3 composite
data-types: compounds, lists and tables.
o Numbers are unbounded, like all data-types in B, and are kept exact if
  possible (even with division);
o Texts can be joined, repeated, trimmed;
o Compounds are like records, or structures, but without field-names;
o Lists are sorted sequences of values of any one type (numbers, texts,
  lists...);
o Tables are generalised arrays: both indexes and elements may be of any type.
 
COMMANDS
The usual structured commands are available: IF, WHILE, etc. You can define
your own commands and functions. Functions can return values of any type.
 
ENVIRONMENT
B is both a language and an environment. There is a structured editor that
knows about B which you use the whole time that you are using B. It suggests
possible command completions, so for instance, if you type a W, it suggests
the command WRITE, which you can accept by typing a tab. It also supplies
such things as closing brackets automatically.
 
EXAMPLES
The best way to appreciate the power and simplicity of B is to see some
examples, and 2 are given below. For more details see "An Overview of the B
programming Language" by Leo Geurts, in SIGPLAN December 1982, and
"Description of B" by Lambert Meertens and Steven Pemberton, SIGPLAN
February 1985.)
 
Imagine you want to maintain a list of phone numbers. You start off with an
empty list (>>> is the prompt from B):
	>>> PUT {} IN tel
and add a few numbers
	>>> PUT 4138 IN tel["Frank"]
	>>> PUT 4071 IN tel["Leo"]
	>>> PUT 4141 IN tel["Lambert"]
Now you can look up individual numbers:
	>>> WRITE tel["Leo"]
	4071
or even write the whole table:
	>>> WRITE tel
	{["Frank"]: 4138; ["Lambert"]: 4141; ["Leo"]: 4071}
(note they're sorted on the names). You can access the list of 'keys' (the
indexes):
	>>> WRITE keys tel
	{"Frank"; "Lambert"; "Leo"}
and so you can write the table neatly:
	>>> FOR name IN keys tel:
	        WRITE name, ":", tel[name] /
	Frank: 4138
	Lambert: 4141
	Leo: 4071
It is easy to discover who has a particular number:
	>>> IF SOME name IN keys tel HAS tel[name]=4141: WRITE name
	Lambert
But if you do this often it is easier to create the inverse table:
	>>> PUT {} IN let
	>>> FOR name IN keys tel:
		PUT name IN let[tel[name]]
	>>> WRITE let[4141]
	Lambert
	>>> WRITE let
	{[4071]: "Leo"; [4138]: "Frank"; [4141]: "Lambert}
 
Example 2: a cross reference generator.
(This example would need more than 100 lines of Pascal or C.)
 
HOW'TO INDEX text:
    PUT {} IN xtab
    FOR line'no IN keys text:
        TREAT'LINE
    OUTPUT
TREAT'LINE:
    PUT text[line'no] IN line
    WHILE line>"": TREAT'WORD
TREAT'WORD:
    GET'WORD
    IF word>"": SAVE'WORD
GET'WORD:
    PUT "" IN word
    WHILE line>"" AND NOT alpha:
        PUT line@2 IN line
    WHILE line>"" AND alpha:
        PUT word^line|1, line@2 IN word, line
alpha:
    REPORT line|1 in {"a".."z"} OR line|1 in {"A".."Z"}
SAVE'WORD:
    IF word not'in keys xtab:
        PUT {} IN xtab[word]
    INSERT line'no IN xtab[word]
OUTPUT:
    FOR word IN keys xtab:
        WRITE word<<10
        FOR line IN xtab[word]:
            WRITE line>>4, " "
        WRITE /
 
 
THE IMPLEMENTATION
o Requires at least 384K bytes to run, though there is a restricted version
  without the built-in editor that runs in 256K.
o Runs under MS-DOS 2.0 or higher.
o Configurable for different size screens, or to use the ANSI screen driver,
  for compatibles with incompatible BIOS.
o Editing operations can be bound to the keys of your choice.
o Comes on a single 5.25" or 3.5" diskette. Apricot format also available.
o It is not copy protected.
But:
o It is not a production version: it is not fast, but it is fun!
 
WHAT YOU GET
Apart from the floppy, you get a book introducing B, how to use the system,
and giving a complete description of the language, and a quick reference
guide.
 
HOW TO ORDER
Fill in the details below, and send them with a cheque or money order for
$35 US or Dfl. 100 (to cover cost of media, postage, etc.) payable to
Stichting Mathematisch Centrum, Amsterdam to:
	B Group, PC Distribution
	Informatics/AA
	CWI
	POB 4079
	1009 AB Amsterdam
	The Netherlands
 
Name:
Organisation:
Address:
Country:
Telephone:
Network address:
 
Type of machine(s):
 
Required media
[ ] 5.25" double-sided, double density floppy
[ ] 3.5" double-sided floppy
 
Required version
[ ] Full implementation (at least 384K bytes)
[ ] Small version (256K bytes)
 
Signature and date: