TAL Reference Manual

Expressions
TAL Reference Manual—526371-001
4-8
Signed Arithmetic Operators
A positive fpoint specifies the number of decimal places to the right of the decimal
point:
FIXED(3) x := 0.642F; !Stored as 642
A negative fpoint specifies a number of integer places to the left of the decimal point.
To store a FIXED value, a negative
fpoint truncates the value leftward from the decimal
point by the specified number of digits. When you access the FIXED value, zeros
replace the truncated digits:
FIXED(-3) y := 642945F; !Stored as 642; accessed
! as 642000
When FIXED operands in an arithmetic expression have different fpoints, the system
makes adjustments depending on the operator.
•
In addition or subtraction, the system adjusts the smaller fpoint to match the larger
fpoint. The result inherits the larger fpoint. For example, the system adjusts the
smaller
fpoint in 3.005F + 6.01F to 6.010F, and the result is 9.015F.
•
In multiplication, the fpoint of the result is the sum of the fpoints of the two
operands. For example, 3.091F * 2.56F results in the FIXED(5) value 7.91296F.
•
In division, the fpoint of the result is the fpoint of the dividend minus the fpoint of
the divisor. (Some precision is lost.) For example, 4.05F / 2.10F results in the
FIXED(0) value 1.
To retain precision when you divide operands that have nonzero
fpoints, use the
$SCALE standard function to scale up the
fpoint of the dividend by a factor equal to the
fpoint of the divisor; for example:
FIXED(3) result, a, b; ! fpoint of 3
result := $SCALE(a,3) / b; !Scale A to FIXED(6); result
! is a FIXED(3) value
The following example shows how the system makes automatic adjustments when
operands in an expression have different
fpoints: