Directory of image this file is from
This file as a plain text file
SSS N N OOOOO BBBB OOOOO L 888 222
S S NN N O O B B O O L 8 8 2 2
S N N N O O B B O O L 8 8 2
SSS N NN O O BBBB O O L 888 222
S N N O O B B O O L 8 8 2
S S N N O O B B O O L 8 8 .. 2
SSS N N OOOOO BBBB OOOOO LLLLL 888 .. 22222
UU UU SSSSSS EEEEEEEEEE RRRRRRRR ''' SSSSSS
UU UU SS SS EE RR RR ''' SS SS
UU UU SS EE RR RR ''' SS
UU UU SSSSSS EEEEEE RRRRRRRR SSSSSS
UU UU SS EE RR RR SS
UU UU SS SS EE RR RR SS SS
UUUUUU SSSSSS EEEEEEEEEE RR RR SSSSSS
MM MM AAAAAA NN NN UU UU AAAAAA LL
MMMM MMMM AA AA NNNN NN UU UU AA AA LL
MM MM MM AA AA NN NN NN UU UU AA AA LL
MM MM MM AAAAAAAAAA NN NNNN UU UU AAAAAAAAAA LL
MM MM AA AA NN NN UU UU AA AA LL
MM MM AA AA NN NN UU UU AA AA LL
MM MM AA AA NN NN UUUUUU AA AA LLLLLLLLLL
SSS N N OOOOO BBBB OOOOO L 888 222
S S NN N O O B B O O L 8 8 2 2
S N N N O O B B O O L 8 8 2
SSS N NN O O BBBB O O L 888 222
S N N O O B B O O L 8 8 2
S S N N O O B B O O L 8 8 .. 2
SSS N N OOOOO BBBB OOOOO LLLLL 888 .. 22222
UU UU SSSSSS EEEEEEEEEE RRRRRRRR ''' SSSSSS
UU UU SS SS EE RR RR ''' SS SS
UU UU SS EE RR RR ''' SS
UU UU SSSSSS EEEEEE RRRRRRRR SSSSSS
UU UU SS EE RR RR SS
UU UU SS SS EE RR RR SS SS
UUUUUU SSSSSS EEEEEEEEEE RR RR SSSSSS
MM MM AAAAAA NN NN UU UU AAAAAA LL
MMMM MMMM AA AA NNNN NN UU UU AA AA LL
MM MM MM AA AA NN NN NN UU UU AA AA LL
MM MM MM AAAAAAAAAA NN NNNN UU UU AAAAAAAAAA LL
MM MM AA AA NN NN UU UU AA AA LL
MM MM AA AA NN NN UU UU AA AA LL
MM MM AA AA NN NN UUUUUU AA AA LLLLLLLLLL
SNOBOL-8.2 User's Manual
INTRODUCTION
SNOBOL-8.2 is an improper subset of SNOBOL-3 [Forte 67] implemented for
any PDP-8 computer operating under the OS/8 operating system. The
restrictions to SNOBOL-3 consist of an absense of functions and extended
arithmetic statements. SNOBOL-8.2 is in turn extended by allowing the
programmer access to PDP-8 assembly language code within his/her program
and also access to OS/8 for opening, closing and manipulating OS/8
files. The inexperienced user is referred to Allen Forte's SNOBOL-3
Primer which gives a good, simple introduction to the language. This
document is designed to underline the highlights of SNOBOL-3 as
reflected in SNOBOL-8.2 as well as to detail the specific implementation
of SNOBOL-8.2.
Author: Fred Dalrymple
Northwestern University
Computer Science Research Laboratory
Technological Institute Room B626
Evanston, Illinois 60201
Updated: William Nowicki
December 4, 1976
SNOBOL-8.2 User's Manual
TABLE OF CONTENTS
I. Data
1. Literals 1
2. Variables 1
3. Special Variables 1
4. Special Codes 2
5. Variable Contents 3
6. Indirect Variables 3
7. Labels 3
8. Transfers 4
9. Comments 4
II. "Period Compiler Commands
1. .PUSHJ, .PUSH, .POPJ, .POP 5
2. .PAL and .SNOBOL 5
3. .EXIT 6
4. .END 7
5. .LOOKUP 7
6. .ENTER 7
7. .ICLOSE 7
8. .OCLOSE 7
9. More on Files 7
III. Arithmetic Operations
1. Arithmetic Capabilities 9
2. Bases 10
IV. Pattern Matching
1. Simple Replacement 11
2. Simple Search
a. non-anchor mode 11
b. anchor mode 12
3. Fillers
a. Free Length Fillers 12
b. Fixed Length Fillers 13
4. Or 13
5. Delete
a. Without Replacement 14
b. With Replacement 14
6. No Backup 14
7. POSR 15
SNOBOL-8.2 User's Manual
V. The Compiler
1. The Command String 16
2. Error Messages 16
3. Assembling the PAL file 16
4. Loading the Binary File 16
VI. The Run Time System
1. Fatal Errors 17
2. Continuing After a Control C 17
I. Data
There are two methods by which to specify data in the form of a
character string. The first is to enter the string in quotes (a
literal), the second is by storing the string in a variable.
Variables may be assumed to be empty (null) at the beginning of the
program.
Literals and variables may be used inter-changeably anywhere a
reference to a string is allowed. For example:
VARIABLE = 'STRING' is valid
'STRING' = 'NEW VALUE' is not
I.1 Literals
A literal is any string of characters delimited at both ends by
either a single or double quote. The string cannot contain the
delimiter, but may contain any other character. For example:
'THIS IS A LITERAL'
"AND THIS"
"THIS 'IS' TOO" Double quotes capture
the singles
'BUT THIS IS NOT" Different types of quotes
'THIS ISN'T EITHER' String contains the delimiter
I.2 Variables
A variable name is any sequence of alphanumerics and numerics that
begins with at least one alphanumeric (except "X", which is
reserved). Only the first six characters are significant, so that
'ABCDEFG' and 'ABCDEFZ' are equivilent. No PAL8 reserved symbol or
pseudo-op can be used as a variable name since the output of the
SNOBOL compiler is passed through PAL8.
I.3 Special Variables
Certain names are restricted to special meanings having to do with
input/output functions. A reference to one of these names will have
the effect as described below:
INPUT value is a new line of text from the console
OUTPUT *value is typed on the console, followed by a
return-line feed
OUTHOLD *value is typed on the console without a
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SNOBOL-8.2 User's Manual
return-line feed
READ value is the next line from the currently
open input file
WRITE *value is written on the currently open output
file, followed by a return-line feed
WRITEH *value is written without the return-line feed
Input variables (non *) may be used wherever a variable reference is
allowed. Output variables (*) may only be assigned values, which are
processes when variable assignment takes place. Reference to an
output variable in an input context, for example:
NAME = OUTPUT
Will result in a value of the null string assigned to NAME.
Reference to an input variable in an output context will be ignored
at run time (no assignment takes place). The READ function will fail
if either the input file has been exhausted or none is currently
open. A WRITE or WRITEH function will fail if either there is no
open output file, or it is full. A function failure causes the entire
statement in which it occurs to fail.
The following sample program causes the file 'IFILE.TX' on the OS/8
DSK device to be typed in its entirety:
.LOOKUP 'IFILE.TX' :F(END) /open the input file
LOOP, OUTPUT = READ :S(LOOP) /type all the input lines
END, .END
A line of input is always terminated by the RETURN character (ASCII
octal 215). Line feeds, form feeds, etc. (212-214) are ignored on
input in normal mode. See the support routine description for more
information.
I.3 Special Codes
Any single character that the user is reticent to enclose is quotes
may be equally well repesented in the form:
.Annn
where nnn is the octal ASCII code of the character to be represented.
Any code 1 through 377 is valid. For example, .A214 can be used to
generate a form feed character.
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SNOBOL-8.2 User's Manual
I.5 Variable Contents
The value of a variable may be assigned by the SNOBOL-8.2 statement:
NAME = 'string'
After the execution of this statement, examination of the variable
'NAME' will show its contents to be the literal 'string' (not
including the quotes). Further characters may be concatenated to the
end of the characters in NAME by the statement:
NAME = NAME ", AND MORE"
NAME now has the value 'STRING, AND MORE'. We may delete the value
of NAME by either of the statements:
NAME = ''
Or NAME =
I.6 Indirect Variables
The prefix "@" to a name or literal has the effect of referencing not
that name or literal, but the variable named by the original string.
For example,
STR = 'NAME'
NAME = 'THIS IS A STRING'
@STR has the value 'THIS IS A STRING'.
Also, transfers may be made to @NAME if NAME contains the name of a
label within this program.
One note of caution when using this feature: the compiler produces a
possibly lengthy table to allow this function to work. If space is
limited, it would be worthwhile to not use this feature.
I.7 Labels
Labels are used to identify lines of the SNOBOL-8.2 program. The
name used as a label must conform to the same conventions as for
variable names, e.g. no more than six significant characters make up
a name. No label may have the same name as a variable or other label.
The label must be the first element of a line and must be terminated
by a comma. For example:
LABEL, STR = "string"
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SNOBOL-8.2 User's Manual
I.8 Transfers
The flow of a program may be altered by a transfer command. The
transfer may be made either unconditionally or under a certain
condition of the success-fail indicator, the setting of which is
discussed below. The format of the unconditional transfer is as
follows:
:(LABEL)
The format of the success and fail, respectively, transfers is as
follows:
:S(LABEL) /transfers to LABEL on success
:F(LABEL) /transfers to LABEL on failure
Transfers for success and failure may be grouped together:
:S(LABEL1)F(LABEL2)
:F(LABEL2)S(LABEL1)
Both of these forms transfer to LABEL1 on success and LABEL2 on
failure.
Transfers should be the last executable element of the source line
(they may be alone on a line) and should follow any command (except
.PAL or any section of PAL code). The transfer should immediately
preceed any comment.
I.9 Comments
Any slash not captured within quotes (i.e. within a literal) and all
characters to the right of the slash are treated as a comment and is
ignored by the compiler:
LABEL, STR = /purge STR (this is a comment)
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SNOBOL-8.2 User's Manual
II. Period Compiler Commands
All commands preceeded by a period should immediately follow any
label (if specified) and immediately preceed any transfer (if
specified).
II.1 .PUSHJ, .PUSH, .POPJ and .POP
.PUSHJ is a stack operator which allows transfer of control to any
label in the program. .POPJ transfers control to the point
immediately following the most recent .PUSHJ that was executed.
(I.E. any transfer on the same line, otherwise the next executable
statement. .PUSH and .POP can be used as general stack operators.
Much care should be taken to be sure that every .PUSH(J) has a
corresponding .POP(J), since the same stack is used for both
variables and lables.
An example of the use of these commands follows:
.PUSH VAR Push the argument on the stack
.PUSHJ LABEL This is equivalent to a
subroutine call
LABEL,
.POP ARG Pop the argument off the stack
...
.POPJ This statement returns
from the subroutine
Up to 32. .PUSHJ's may be made at one time. If 32. .PUSHJ's have been
made, and another .PUSHJ is executed before a .POPJ, then the run
time system will signal this condition and the program will stop.
II.2 .PAL and .SNOBOL
There are two methods by which to enter the mode where the compiler
expects PAL-8 code as input. The first is the .PAL command. For
example:
.PAL nn
PAL code goes here
^.SNOBOL
where nn is the number of locations (in octal) that the PAL code will
require. The compiler assumes a '.SNOBOL' at the beginning of every
program. The PAL-8 code between the .PAL statement and the .SNOBOL
statement will not be broken up by a page boundary.
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SNOBOL-8.2 User's Manual
The second method of entering PAL code is by prefixing an uparrow to
the beginning of each PAL line. The uparrow has the effect of
changing the compiler mode for that line; i.e. is in SNOBOL mode, the
uparrow signals a line of PAL code, if in PAL mode, the uparrow
signals a line of SNOBOL code. A double uparrow reserves two words
for the line of PAL code. Note that an uparrow is needed in PAL mode
for the .SNOBOL statement. Examples:
.SNOBOL /Implicit
^^ TAD (255 /Save two words - one for TAD and
/ one for the literal
^ DCA 50 /Save one location
.PAL 4 /Four words:
TAD (562 /Two
CMA IAC /One
DCA 62 /One
^ OUTPUT = NAME /One line of SNOBOL
^ .SNOBOL /change back (note uparrow)
A note of caution: the compiler will determine if four more words
(".PAL 4") will fit on the present memory page. If not, then it
starts a new page. If the line of SNOBOL code we inserted (OUTPUT =
NAME) will not fit on the page with the four from the PAL command,
the compiler will put the code for the SNOBOL command on a new page.
It is therefore desireable to break up large sections of PAL code to
smaller sections so as not to waste space if all does not fit onto
one page, whereas part may.
SNOBOL-8.2 inserts a page bounds where-ever needed and handles the
jump over the bounds. It is possible that a break may occur between
the following two lines:
^ TAD 30
^ DCA 40
While the ACC is preserved as well as the program flow, if the
following two lines were broken up, the results would be unexpected:
^ SMA
^ JMP LABEL
II.3 .EXIT
This command causes a jump to location 7600 (the starting address of
OS/8). To restart the SNOBOL-8.2 program:
^C
.START 200
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SNOBOL-8.2 User's Manual
II.4 .END
This command marks the end of the program and generates a .EXIT.
This statement is largely aesthetic, as the compiler will compile
further statements.
II.5 .LOOKUP VAR or 'NAME.EX'
This command looks up the specified file on device DSK and readies it
for input. The success-fail indicator is set to success if the file
is found; if not, to failure.
II.6 .ENTER VAR or 'NAME.EX'
This command readies a file for output on device DSK. If there is
room and not a file already open, the success-fail indicator is set
to success, otherwise failure.
II.7 .ICLOSE
This command closes the input file (if one was open). It always
succeeds.
II.8 .OCLOSE
This command closes the output file (if one was open), and enters it
into the directory for the device DSK of the OS/8 system. If the file
was open and was able to be closed, the success-fail indicator is set
to success, otherwise failure.
II.9 More On Files
SNOBOL-8.2 files are EDITor compatible, so that any file that can be
EDITed or listed by PIP is available for reading by SNOBOL-8.2. In
normal mode any page format is lost since all form feeds are ignored.
Similarly, any file written by SNOBOL-8.2 in normal mode is available
to any standard OS/8 files program. No control Z (the OS/8 end of
file mark) is output unless explicitly done by the user; thus, on
reading the file into the EDITOR the user may obtain a "?".
The user is able to specify any device for his file I/O by modifying
certain locations in the run-time system. By using XDEVS as an
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SNOBOL-8.2 User's Manual
indirect pointer to two, standard, two-word device name blocks in
field zero (the first is the input device, the second, the output
device), one can change the default input and output devices
referenced by the file I/O. They are initially set to DSK and must
be changed before the correspondent .LOOKUP OR .ENTER.
The user can also set the maximum size of the output file by putting
the size in location XFILSIZ. The symbols XDEVS and ZFILSIZ are
defined in SNORTS.PR and may be referenced by PAL code. See the
support routine writeup for more information.
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SNOBOL-8.2 User's Manual
III. Arithmetic Operations
III.1 Arithmetic Capabilities
Number have two representations. First, and most obvious, is
represented by the following statement:
NUM1 = '52'
NUM1 now contains the literal string "52". In this form, there is no
way to add another number to this string and get the sum as a string
(without extensive pattern matching). What is needed is a routine to
transform the string "52" into, the other representation, an octal
number. This form may have arithmetic operations performed on it (via
PAL machine code).
SNOBOL-8.2 allows the operations + and - between strings (that are
converted into octal first and then translated back into strings
after the operations). The form is:
NAME = A op B op C . . .
Where op is either + or -, which cause the expected operations to
take place on A, B, etc.
For more exotic operations, PAL code sequences may call the run time
system routines XASC and XINT to convert the string to octal, and the
other direction. Note that SNOBOL-8.2 operates on strings only and
cannot handle octal representations of numbers.
The calling sequence for XASC is:
.PAL 2
JMS I XASC /XASC is defined in SNORTS.PR
NAME /where NAME is a SNOBOL varaible
^.SNOBOL /the value of NAME is
/Returned in the ACC
The calling sequence for XINT is:
.PAL 2 /the octal number to be converted
JMS I XINT /should be in the ACC
NAME /NAME will hold the string
^.SNOBOL
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SNOBOL-8.2 User's Manual
III.2 Bases
Both XASC and XINT will operate in any base (greater than one). The
base is initially set to 10. No aesthetics are applied (e.g. 10, base
11 = ":"; 11, base 12 = ";").
The base is stored as a binary number in location XBASE (defined in
SNORTS.PR). Note that since a twelve bit binary number is used, any
numeric value must be between 2047 decimal and -2048.
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SNOBOL-8.2 User's Manual
IV. Pattern Matching
IV.1 Simple Replacement
This has already been explained by I.4, but it will be briefly
re-stated here. The basic form of this command is:
<variable name> = <list>
where <list> is made up of variables and literals only. If <list> is
missing, then <variable name> will be the null string. The effect of
this statement is to concatenate all the strings in <list>, which
becomes the new value of <variable name>.
IV.2 Simple Search
2.a Non-anchor Mode
To search a string for the sequence as characters in another string,
one uses a search:
BASE = 'THIS IS THE BASE STRING'
MATCH = 'BASE'
BASE MATCH
The last statement will search the string contained in BASE for the
string contained in MATCH. This command will succeed (set the
success indicator) because the characters 'BASE' (in the variable
MATCH) do match those same characters within the base string 'THIS IS
THE BASE STRING'. However,
MATCH BASE
will fail, because MATCH does not contain all the characters in BASE.
If we search for a list of items, the items are concatenated, and the
resulting string is searched for:
MATCH2 = 'STRING'
BASE MATCH MATCH2
Will fail because when MATCH and MATCH2 are concatenated, the
resulting string is 'BASESTRING'. The following will succesfully
match:
BASE MATCH ' ' MATCH2
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SNOBOL-8.2 User's Manual
2.b Anchor Mode
This pattern matching mode, invoked by a underscore immediately
following the base string (the string being searched through), causes
the pattern matcher to fail unless the string being searched for
begins at exactly the beginning of the base string. Sometimes the
underscore is printed as a backarrow. For example:
BASE = 'THIS IS THE BASE STRING'
BASE_ 'THIS IS' will succeed, while:
BASE_ 'BASE' will not.
IV.3 Fillers
3.a Free Length Fillers
It is possible to match an arbitrary number (up to 511) of characters
of the base string by the use of fillers. The string to be matched
by a filler must be delimited by either the end of the base string or
a variable that matches part of the base string. A filler matches
the least number of characters possible to allow the pattern match to
succeed. For example:
BASE = ',AND,TAD,ISZ,'
Suppose that we want to match and subsequently access the string
delimited by the first two commas in BASE. We could specify:
BASE ',' *BETWN* ','
The action of the run time system is to first match the comma, which
is found in BASE immediately. Then, the filler is noted and the
match continues for the second comma. When the second comma is
found, the pattern match is determined to have succeeded, and the
characters passed over while searching for the second comma are
assigned to the variable BETWN. No variable assignment occurs unless
the entire pattern matching statement succeeds (see IV.8).
Suppose that we wish to similarly access the second string delimited
by commas in BASE. We could specify:
BASE ',' ** ',' *BETWN* ','
The run time system will follow essentially the same procedure,
except that the variable named within '**' is a write-only variable,
its value will be thrown away.
Note that by the use of fillers, the base string is not modified (see
IV.5).
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SNOBOL-8.2 User's Manual
3.B Fixed Length Fillers
It is possible to specify the length of a filler. In this case, the
filler must match exactly the specified number of characters in the
base string, else the entire statement will fail. The form is:
BASE = 'ABCDEFGHIJK'
BASE *LETRS/6*
This statement specifies the assignment of the first six chraracters
in BASE to the variable LETRS, so LETRS will contain 'ABCDEF'.
LEN = '3'
BASE *LETRS/LEN*
This latter statement will assign 'ABC' to LETRS. Similarly, if we
wish to skip three characters and then get the next three:
BASE */3* *INSIDE/3*
INSIDE will be 'DEF'.
IV.4 Or
It is further possible to match either one sequence of characters or
another, up to an arbitrary number of choices. The choices are
seperated by exclaimation points, read 'or'. For example:
BASE = 'FIRST, THIS. AND;THEN'
OTHER = ';'
BASE *SEG* ' '!'.'!','!OTHER
SEG will contain all of the characters up to, but not including the
first of the options to match. So, in this case, SEG will match
'FIRST' and the comma will be matched.
Consider:
BASE *SEG/4* ' '!','!';'
SEG will match the first four characters of BASE, but since one of
the choices must match the next character in the base string, the the
pattern match will fail. SEG will not be assigned a value.
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SNOBOL-8.2 User's Manual
IV.5 Delete
5a. Without Replacement
Suppose that we wish to delete the portion we have matched in the
base string from the base string to leave us only the unmatched
portion of the base string. This may be performed by use of the
equal sign:
BASE = 'ABCDEFG'
BASE *CHAR/1* =
The equal sign follows the search list and all fillers. In this
case, CHAR will contain 'A' and BASE will contain 'BCDEFG'. Another
example:
BASE = 'TAD.,AND.,'
BASE ',' *SEG* ','!'.' =
In this example, BASE will contain 'TAD.,' and SEG will contain
'AND'. The write only filler is useful for selective deletion, for
example, to delete everything between two periods use:
BASE "." ** "." =
5b. With Replacement
If a list of variables and literals apprear to the right of the equal
sign, then not only is the matched portion of the base string
deleted, but also it is replaced by the concatenation of the strings
from the list. For example:
BASE = 'TAD,AND'
ELEMNT = 'ISZ'
BASE ',' = ';' ELEMNT ';'
BASE is searched for a comma, which is found and deleted and then
replaced by the list. BASE will have the contents 'TAD;ISZ;AND'.
IV.6 No Backup
This non-standard feature is best illustrated by an example:
BASE = 'ABCDEFG'
BASE 'A'!'B' 'C'
What is the operation of the run-time system in evaluating this
latter statement? First, it matches the 'A' against the first 'A' in
BASE. Next, it must attempt to match 'C' against the next character
in BASE. However, clearly this will fail, because the next character
PAGE 15
SNOBOL-8.2 User's Manual
in BASE is a 'B' and not a 'C'. So, the run-time system 'backs up'
to the 'A' or 'B' option stage because if it makes another choice (in
this case 'B') then it is possible that the 'C' will match when it
comes time. This time the run-time system chooses the 'B', and then
finds that the 'C' does match, so the statement will succeed.
However, the character '<' when used in a pattern match (before any
delete, if it is used) causes the run-time system to not be able to
back up beyond that point; Therefore the following example would
fail:
BASE 'A'!'B' < 'C'
IV.7 POSR
This special variable (available only within the pattern matching
statement) matches only the end of the base string. It therfore can
be thought of as the inverse of the underscore (anchor mode). If the
base string has not been matched fully to its end when POSR is
encountered, then this function will fail. For example:
BASE = "ABCDEFG"
BASE "G" POSR
BASE "A" "C"!POSR
The first pattern match above will fail, the second will succeed.
IV.8 Filler and Base String Assignment
All variable assignments (fillers and deletion/replacement of the
base string) are performed at the end of the pattern matching
statement, and only if the statement was successful. This is in
partail difference with other SNOBOL-3 implementations, for example:
BASE = '"THIS IS A LITERAL"'
BASE *QUOTE/1* *LITRL* QUOTE
Other implementations have allowed the assignment of QUOTE before the
end of the pattern matching, and hence the second instance of QUOTE
will match the character in BASE that is the same as the first
character that was matched by *QUOTE/1*. This is not the action of
SNOBOL-8.2, this statement would have to be broken up into the two
pattern matching statements:
BASE *QUOTE/1*
BASE QUOTE *LITRL* QUOTE
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SNOBOL-8.2 User's Manual
V. The Compiler
V.1 The Command String
The SNOBOL-8.2 compiler uses the CD function of OS/8 and is therefore
compatible with the command strings of other OS/8 systems programs.
The compiler produces one output file - a PAL file to implement the
SNOBOL-8.2 code. Up to nine input files may be specified to be
concatenated into one large source program. The ".SN" extension is
assumed for input files to the compiler.
V.2 Error Messages
If and when the compiler detects an error in the input source file,
the erroneous line is typed, an uparrow is typed directly under the
point at which the error was detected, and a descriptive message is
given explaining the error.
V.3 Assembling the PAL file
The PAL file must be assembled with the parameter file SNORTS.PR:
.R SNOBOL
*FILE.PA<FILE.SN
.R PAL8
*FILE.BN,<SYS:SNORTS.PR,FILE.PA
Error messages will be printed if the program is too long.
V.4 Loading the Binary File
The binary file must be loaded with the run time system SNORTS.BN.
.R ABSLDR
*SNORTS.BN,FILE.BN
*^C
.
If CCL is available, the following commands can be used:
.R SNOBOL
*FILE<FILE
.PAL SNORTS.PR-NB,FILE
.LOAD SNORTS,FILE/G
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SNOBOL-8.2 User's Manual
VI. The Run Time System
VI.1 Fatal Errors
Certain fatal errors of the run time system will result in the output
of a message of the form:
?SNORTS n
where n specifies which error occurred:
0 - Pushdown list overflow
1 - Pushdown list underflow
2 - Indirect name not found
Other n specify internal errors of the run time system and indicate
bugs in same. These should be referred to the appropriate person(s).
3, 4 - Pattern matching calling list error
5, 6 - Pattern matching base string size error
7 - Error deleting string - bad format of variable
VI.2 Continuing After a Control C
It is possible to continue a SNOBOL-8.2 program if a control C was
typed during its execution by typing:
^C
.START 154
Also, SNOBOL-8.2 programs are not self-modifying (unless PAL code
inserted by the user invalidates this) and therefore may be
re-started any number of times at location 200.