Rockwell Automation 57C610 Enhanced Basic Language, AutoMax - Manual (Page 39)

5Ć7
The following are relational expressions:
A% > B%
((A%+3)/16) < > 32
(((A%/25) +13)+B%) >= SPEED%
(A% < > B%) OR (GAIN => 3.58867) OR (FAULTS% = 0)
(MESSAGE$ = SYSTEM DOWN")
(SPEED > OLD_SPEED + 23.8876/GAIN)
Since the result of a relational expression is a true or false value
(boolean result), several relational subĆexpressions may be
combined by using the boolean operators AND, OR, and XOR.
The following are statements using relational expressions:
10 IF (A% > B%) THEN 200
10 IF (SPEED < 32.887) AND (SECTION 5_on@) THEN
GOSUB 12000
10 IF SYSTEM STOPPED@ OR FAULTS@ OR (ROLL_
WIDTH% <23) THEN 240
5.5 Mixed Mode (Integers and Reals)
Arithmetic
In performing mixed mode arithmetic (expressions in which integers
and reals are intermixed), BASIC must always convert the integer
value to a real or decimal number internally to be able to operate on
the two quantities.
The integer must be converted to a real to maintain the maximum
amount of precision possible. (Converting the real to integer and
doing all integer arithmetic obviously is not feasible because all the
fractional parts would be lost; A=2.37764+4 should result in
6.37764 not 6.) This integerĆtoĆreal conversion happens only,
however, at the point where the integer value or subĆexpression
value is combined with a real value in an operation.
When BASIC evaluates an expression. it follows certain rules which
determine the order of evaluation in the expression. When using
mode arithmetic, use caution to assure the desired results.
If there are integer parts to the expression, BASIC will use integer
arithmetic until it encounters a real value and then convert the
integer partial result to real. For example, the following expression is
evaluated exactly as seen, left to right (because there are not
parentheses and all the operators are of the same precedence or
importance):
REAL3 = B% * C% * D% * REAL1 * REAL2
The above statement is evaluated as follows:
1. B% * C% will be calculated in integer arithmetic.
2. The intermediate value of (B% * C%) is then multiplied by D%
using integer arithmetic because both quantities are still
integers.
3. The intermediate value of [(B% * C%) * D%] is now multiplied by
REAL1, but since one of the values is real and one is integer, the
intermediate value of [(B% * C%) * D%] must be converted to a
real value before the multiplication by REAL1.