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27Mar74
SCAT2
VERSION 2 OF
STANDARD COMPLEX ALGEBRA TRANSLATOR FOR PDP-10
AUTHOR: C.J. ANDREWS
DATE: 26-MAR-74
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1.0 INTRODUCTION
SCAT2 is a program written in MACRO-10 for the pdp-10 and is
the second version of SCAT previously described [1]. It is
designed particularly for those who make many repetitive
calculations using complex numbers, for example, in electrical
circuit theory, and in antenna, transmission line and waveguide
theory. Such calculations are tedious to perform, and subject to
error. SCAT2 enables the use r to operate the computer as a
sophisticated desk calculator with predefined functions.
Where SCAT [1] would only accept a single operator between
numbers and variables, SCAT2 will accept full arithmetic
expressions with operator precedence, and use of braces to
indicate evaluation precedence of sub-expressions. Its only
minor limitation is that the unary minus operator is not
permitted.
the input format has been altered to allow a more logical
command construction, with assignment (if desired) appearing at
the beginning of the command. a full range of switches is also
permitted.
Each of these facilities is described in subsequent sections
of this manual.
[1] andrews, c.j., "Standard Complex Algebra Translater for PDP-10",
Computer Centre Bulletin, June 73.
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2.0 COMMAND ELEMENTS
This section describes the various elements which may be
included in a command, except switches, which are dealt with in
section 4.
2.1 COMPLEX NUMBERS
Complex numbers are input to SCAT2 enclosed in parentheses,
the real and imaginary parts being separated by a comma. If
either part is ommitted, it is assumed zero, provided that if
only one number appears between the parentheses it i s assumed to
be the real part of the complex pair, and the imaginary part
zero.
The numbers themselves may be integers, floating point, or
E-format, or a mixture of these. All calculation is, however
performed in floating point.
The following are legal complex pairs:
(1.0,2.0) (1,2) (.01E2,20.E-1)
(1.0,) (1,) (.001E+3,)
(,2.0) (,2) (,2.0E0)
(1.0) (1) (.1E+1)
2.2 VARIABLES
Values may be assigned to variables (see section 2.3) and
these used in subsequent commands.
The variables are referenced by name, which must start with
an alphabetic character, and may be up to six characters in
length. Subsequent characters may be numeric or alphabetic.
Examples of legal names are:
a abc a12 abcdef zby3
2.3 OPERATORS
Five arithmetic operators are permitted between command
elements, and they are:
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+ - / * ^
Assignment is achieved by preceding the command by a
variable name followed by the assignment operator, _.
SCAT2 indicates when assignment has been made (see section
3.2).
To separate the command into sub-expressions to indicate
precedence in evaluation, the user types the sub-expression
inside braces, [ (shift-k) and ] (shift-m).
2.4 FUNCTIONS
Certain predefined trigonometric functions are allowed in
SCAT2. These are shortened to three characters, and are
indicative of the commonly known functions. they are:
SNH[] - sinh function
CSH[] - cosh function
TNH[] - tanh function
MAG[] - magnitude function
ANG[] - angle function
CAR[] - convert to cartesian form
POL[] - convert to polar form
Suggestions for other needed functions are welcomed, and
endeavour will be made to incorporate them.
2.5 EXAMPLES
The following are examples of valid commands:
(1,2)+(3,4)-(7.01,9.86)/(2.3,8.6)
[[(1.0,)+(,9.3)]*(8.1,3.2)]^(2.1,3.6)
abcd1_[(2.6e1,3.1e-2)*snh[ab+(2.6,5.1)*z1]]^(2,3)
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3.0 OPERATING INSTRUCTIONS AND OUTPUT
3.1 OPERATION
SCAT2 is set in operation in the following manner:
.RU SCAT2[111,132]
SCAT2 (19-MAR-74) READY
*
The asterisk indicates readiness for a command. Once a
command is input SCAT2processes the command in the following way:
(i) It carries out a single pass processing of the command to
"compile" a polish string from it.
(ii) This polish string is then subject to a single scan, and
is executed.
(iii)the results are then output.
SCAT2 inputs the command character by character. This is
done so that immediate processing of switch characters can be
made. This carries with it the limitation that a rubout
character cannot be issued. If an error condition or mistake
occurs an R switch should be used to restart the command (see
section 4.0).
3.2 OUTPUT
3.2.1 ASSIGNMENT
SCAT2 indicates when assignment has been made by outputting
the result of its calculation, and the variable name to which
assignment has been made. For example,
ABC12 = (1.032,-4.301)
3.2.2 NO ASSIGNMENT
When no assignment has been made SCAT2 merely types the
result in the following form:
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RESULT = (1.032e+6,-4.301e-2)
3.3 LIMITATIONS
The operating limitations of SCAT2 are as follows:
(i) Commands may not be extended beyond one line
(ii) No more than 40 variables may be assigned.
(iii)No unary minus is permitted.
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4.0 SWITCHES
A number of single letter switches can be used to instruct
SCAT2 to perform specific functions to assist the user. These
are given in section 4.3.
4.1 SPECIFYING A SWITCH
To specify a switch the user types an "altmode" or "escape"
character. This places SCAT2 in switch mode, and the character
immediately following the altmode or escape is interpreted as a
switch. It is then processed imm ediately, and in most cases
causes some output. The command string however is unaffected by
the action of a switch and may be continued upon termination of
the switch list (see section 4.2).
4.2 TERMINATING THE SWITCH LIST
After processing a switch SCAT2 will accept, and expect,
another. If no further switches are required, an altmode, or
escape, terminates the list.
4.3 SWITCH ACTIONS
4.3.1 D switch
The D switch causes a dump of all variables assigned to
date, and their current values.
4.3.2 E switch
The E switch causes SCAT2 to exit to monitor.
4.3.3 R switch
The R switch causes SCAT2 to restart a command. This switch
causes the current command to be lost.
4.3.4 Q switch
When typing a long command, a user may wish to query if
errors do exist in what has already been typed. The Q switch is
implemented to enable him to do this.
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If no errors exist, SCAT2 automatically outputs a switch
list terminator,and expects the user to continue the command.
If errors do exist, the user is informed, and asked for
another switch, most likely the L switch.
4.3.5 L switch
The L switch will list any errors existing in the current
command. If no errors exist, a switch list terminator is output,
and the command continued. After listing the errors, the program
automatically performs an R switch function.
4.3.6 C switch
The C switch clears the count of errors in the current
command. It does not remedy the errors themselves, but merely
clears the count. For this reason peculiar results may be
encountered when this switch is used, and a command continued.
4.3.7 H switch
The H switch issues a help text to the user, detailing each
of these switches.
4.3.8 X switch
The X switch enables a user to delete variables previously
stored. SCAT2 will ask:
confirm:
to which is typed the list of variables it is desired to
delete. If a '*' is typed in reply, all variables are deleted.
4.3.9 altmode or escape
The altmode, or escape, terminates a switch list and allows
the continuation of a command.
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5.0 ERROR DETECTION
SCAT2 outputs a number of diagnostic error messages in the
event of the occurrence of error conditions.
5.1 "COMPILE" TIME ERRORS
When translating the command into a polish string the
following error messages may occur:
ILL. CHAR IN INPUT
TOO MANY CHARS
UNDEFINED VARIABLE
DELIMITER EXPECTED
EXP OUT OF RANGE
UNBAL PARENTH
5.2 "EXECUTION" TIME ERRORS
During execution of the polish string, the following error
conditions may occur:
too many variables
exec ov/und flow
udf fcn
These are thought to be self-explanatory.
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