Rockwell Automation 57C610 Enhanced Basic Language, AutoMax - Manual (Page 35)

5Ć3
BASIC evaluates expressions enclosed in parentheses before the
operator immediately outside the parentheses, even when the
operator enclosed in parentheses is on a lower precedence level
than the operator outside the parentheses. In the statement A = B*
(C - D), BASIC evaluates the (C - D) first, and then multiplies B by
the result of (C - D).
BASIC will still evaluate other expressions before those in
parentheses if the other expressions come first in the statement and
have a higher precedence. In the statement below, however, the
parenthetical expression occurs later in the overall expression. The
exponentiation operation is performed first (before the parentheses)
because it is encountered first in the leftĆtoĆright evaluation and, at
the time it is encountered, is a higher precedence than any operator
before it.
BASIC evaluates the expression A = B - C**5 + (X*(Z - 17)), in
the following sequence:
C% Exponentiation
B - C% Subtraction with first term
Z - 17 Innermost parenthetical expression
X * (Z - 17) Next level of parentheses
[B - C%] + [X*(Z - 17)] Combination of the two expressions
Arithmetic mixing of both single and double precision integers along
with real variables and constants is permitted in a BASIC statement.
The rules regarding truncation and the maximum size integerĆtoĆreal
conversion still apply.
The following are valid arithmetic mixing examples:
20 GAIN = MOTOR_SPEED%*(OLDGAIN!*13.8876)
or
20 GAIN! = GAIN! + REFERENCE%
The following example could cause an overflow if the resultant value
is larger than 16 bits of precision. In such a case, the largest
possible single positive or negative integer would be loaded into the
variable GAIN%. The program would continue to run, and an error
would be logged to notify the user of the problem.
20 GAIN% = REFERENCE! + GAIN%
5.2 String Expressions
BASIC provides three operations for use with string expressions.
These are the assignment operation (=), the concatenation
(addition of strings) operation (+), and the equality/inequality
comparison operations (=, < >, or > < ).
By using the assignment operator, you can equate or assign one
string variable or constant to another string variable. In the
statement below, the character sequence THIS IS A MESSAGE" is
assigned to the string variable C$:
C$ = THIS IS A MESSAGE"
The concatenation operator (+) combines string variables and
constants to form a new string expression:
C$ = HI" + B$ + D$ + STRING"