EVAL
Format: EVAL <value1> {[<operation>] [<value2>]} [TO<file>]
[LFORMAT=<string>]
Template: VALUE1/A, OP, VALUE2/M, TO/K, LFORMAT/K
Purpose: To evaluate simple expressions.
Path: C:EVAL
Specification:
EVAL is used to evaluate and print the answer of an integer expression. The
fractional portion of input values and final results, if any, are truncated
(cut off). Decimals are not allowed, evaluation stops at the decimal point.
<Value1> and <value2> may be decimal, hexadecimal, or octal numbers. Decimal
numbers are the default. Hexadecimal numbers are indicated by either a
leading 0x or #x. Octal numbers are indicated by either a leading 0 or a
leading #. Alphabetical characters are indicated by a leading single quote
(').
The output format defaults to decimal; however, you can use the LFORMAT
keyword to select another format. The LFORMAT keyword specifies the
formatting string used to print the answer. You may use %X (hexadecimal), %O
(octal), %N (decimal), or %C (character). The %X and %O options require a
number of digits specifcation (i.e., %X8 gives 8 digits of hex output). When
using the LFORMAT keyword, you can specify that a new line should be printed
by including a *N in your string.
The supported operations and their corresponding symbols are shown below:
Operation Symbol
--------- ------
addition +
subtraction -
multiplication *
division /
modulo mod
AND &
OR |
NOT ~
left shift lsh
right shift rsh
negation -
exclusive OR xor
bitwise equivalence eqv
EVAL can be used in scripts to act as a counter for loops. In that case, the
TO option, which sends the output of EVAL to a file, is very useful.
Parentheses may be used in the expressions.
Example 1:
1> EVAL 64 / 8 + 2
10
Example 2:
1> EVAL 0x5f / 010 LFORMAT="The answer is %X4*N"
The answer is 000B
This divides hexadecimal 5f(95) by octal 10(8), yielding 000B, the integer
portion of the decimal answer 11.875. (The 1> prompt would have appeared
immediately after the 000B if *N had not been specified in the LFORMAT
string.)
Example 3:
Assume you were using the following script, called Loop:
Key loop/a
.Bra {
.Ket }
ECHO >ENV:Loop {loop}
LAB start
ECHO "Loop #" noline
TYPE ENV:Loop
EVAL <ENV:Loop >NlL: to=T:Qwe{$$} value2=1 op=- ?
TYPE >ENV:Loop T:Qwe{$$}
IF val $loop GT 0
SKIP start back
ENDIF
DELETE ENV:Loop T:Qwe{$$} ; clean up
ECHO "done"
If you were to enter:
1> EXECUTE Loop 5
The following results would be displayed:
1> EXECUTE Loop 5
Loop #5
Loop #4
Loop #3
Loop #2
Loop #1
done
The first ECHO command sends the number given as the loop argument, entered
as an argument of the EXECUTE command, to the ENV:Loop file.
The second ECHO command coupled with the TYPE command, displays Loop #
followed by the number given as the loop argument. In this case, it
displays Loop #5.
The EVAL command takes the number in the ENV:Loop file as <value1>, which
makes the question mark at the end of the line necessary. <Value2> is 1, and
the operation is subtraction. The output of the EVAL command is sent to the
T:Qwe{$$} case, the value would be 4. The next IF command sends the value in
the T:Qwe{$$} file to the ENV:Loop file. In this case, it changes the value
in ENV:Loop from 5 to 4.
The IF statement states that as long as the value for Loop is greater than 0,
the script should start over. This results in the next line being Loop #4.
The script will continue until Loop is equal to 0.
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