[unix-history] / usr / doc / ratfor / m0

.....ND "January 1, 1977"
.RP
....TR 55
.....TM 76-1273-10 39199 39199-11
.TL
RATFOR \(em A Preprocessor for a Rational Fortran
.AU "MH 2C-518" 6021
Brian W. Kernighan
.AI
.MH
.OK
structured programming, control flow, programming
.AB
.ps 9
.nr PS 9
.vs 11
.nr VS 11
.in 0
.ll
.PP
Although Fortran is not a pleasant
language to use,
it does have the advantages of universality
and (usually) relative efficiency.
The
Ratfor 
language attempts to conceal
the main deficiencies of Fortran
while retaining its desirable qualities,
by providing
decent control flow statements:
.IP "\ \ \ \(bu"
statement grouping
.IP "\ \ \ \(bu"
.UL if-else
and
.UL switch
for decision-making
.IP "\ \ \ \(bu"
.UL while ,
.UL for ,
.UL do ,
and
.UL repeat-until
for looping
.IP "\ \ \ \(bu"
.UL break
and
.UL next
for controlling loop exits
.LP
and some ``syntactic sugar'':
.IP "\ \ \ \(bu"
free form input (multiple statements/line, automatic continuation)
.IP "\ \ \ \(bu"
unobtrusive comment convention
.IP "\ \ \ \(bu"
translation of >, >=, etc., into .GT., .GE., etc.
.IP "\ \ \ \(bu"
.UL return (expression)
statement for functions
.IP "\ \ \ \(bu"
.UL define
statement for symbolic parameters
.IP "\ \ \ \(bu"
.UL include
statement for including source files
.LP
Ratfor
is implemented as a
preprocessor which translates this language
into Fortran.
.PP
Once the control flow and cosmetic deficiencies of Fortran
are hidden,
the resulting language is remarkably pleasant to use.
Ratfor 
programs are
markedly easier to write, and to read,
and thus easier to debug, maintain and modify
than their Fortran equivalents.
.PP
It is readily possible to write 
Ratfor 
programs which are portable to other env ironments.
Ratfor
is written in itself
in this way,
so it is also portable;
versions of 
Ratfor 
are now running on at least two dozen different types of computers
at over five hundred locations.
.PP
This paper discusses design criteria
for a Fortran preprocessor,
the 
Ratfor
language
and its implementation,
and user experience.
.AE
.FS
This paper is a revised and expanded version of oe published in
.ul
Software\(emPractice and Experience,
October 1975.
The Ratfor described here is the one in use on
.UC UNIX
and
.UC GCOS
at Bell Laboratories, Murray Hill, N. J.
.FE
.CS 12 1 13 0 0 10
Commit	Line	Data
8340f87c BJ	1	.....ND "January 1, 1977"
	2	.RP
	3	....TR 55
	4	.....TM 76-1273-10 39199 39199-11
	5	.TL
	6	RATFOR \(em A Preprocessor for a Rational Fortran
	7	.AU "MH 2C-518" 6021
	8	Brian W. Kernighan
	9	.AI
	10	.MH
	11	.OK
	12	structured programming, control flow, programming
	13	.AB
	14	.ps 9
	15	.nr PS 9
	16	.vs 11
	17	.nr VS 11
	18	.in 0
	19	.ll
	20	.PP
	21	Although Fortran is not a pleasant
	22	language to use,
	23	it does have the advantages of universality
	24	and (usually) relative efficiency.
	25	The
	26	Ratfor
	27	language attempts to conceal
	28	the main deficiencies of Fortran
	29	while retaining its desirable qualities,
	30	by providing
	31	decent control flow statements:
	32	.IP "\ \ \ \(bu"
	33	statement grouping
	34	.IP "\ \ \ \(bu"
	35	.UL if-else
	36	and
	37	.UL switch
	38	for decision-making
	39	.IP "\ \ \ \(bu"
	40	.UL while ,
	41	.UL for ,
	42	.UL do ,
	43	and
	44	.UL repeat-until
	45	for looping
	46	.IP "\ \ \ \(bu"
	47	.UL break
	48	and
	49	.UL next
	50	for controlling loop exits
	51	.LP
	52	and some ``syntactic sugar'':
	53	.IP "\ \ \ \(bu"
	54	free form input (multiple statements/line, automatic continuation)
	55	.IP "\ \ \ \(bu"
	56	unobtrusive comment convention
	57	.IP "\ \ \ \(bu"
	58	translation of >, >=, etc., into .GT., .GE., etc.
	59	.IP "\ \ \ \(bu"
	60	.UL return (expression)
	61	statement for functions
	62	.IP "\ \ \ \(bu"
	63	.UL define
	64	statement for symbolic parameters
65	.IP "\ \ \ \(bu"
66	.UL include
67	statement for including source files
68	.LP
69	Ratfor
70	is implemented as a
71	preprocessor which translates this language
72	into Fortran.
73	.PP
74	Once the control flow and cosmetic deficiencies of Fortran
75	are hidden,
76	the resulting language is remarkably pleasant to use.
77	Ratfor
78	programs are
79	markedly easier to write, and to read,
80	and thus easier to debug, maintain and modify
81	than their Fortran equivalents.
82	.PP
83	It is readily possible to write
84	Ratfor
85	programs which are portable to other env ironments.
86	Ratfor
87	is written in itself
88	in this way,
89	so it is also portable;
90	versions of
91	Ratfor
92	are now running on at least two dozen different types of computers
93	at over five hundred locations.
94	.PP
95	This paper discusses design criteria
96	for a Fortran preprocessor,
97	the
98	Ratfor
99	language
100	and its implementation,
101	and user experience.
102	.AE
103	.FS
104	This paper is a revised and expanded version of oe published in
105	.ul
106	Software\(emPractice and Experience,
107	October 1975.
108	The Ratfor described here is the one in use on
109	.UC UNIX
110	and
111	.UC GCOS
112	at Bell Laboratories, Murray Hill, N. J.
113	.FE
114	.CS 12 1 13 0 0 10