Interaction operator |
Description |
Alternative (alt) |
An alternative interaction operator represents the logic equivalent
of an if-then-else statement. Only one of the offered alternatives runs on
any pass through the interaction. However, as is true of any operand, the
selected operand in the alternative structure runs only if the guard condition
tests true. If there is no guard, the operand always runs
when it is selected. The else clause of the alternative combined fragment
runs when no other option is selected. |
Option (opt) |
An option interaction operator represents the logic equivalent of
an if statement. To be used, the guard condition must be satisfied. If the
guard condition fails, the behavior is ignored. The graphic representation
of an option combined fragment looks like an alternative that offers only
one alternative. |
Loop |
A loop interaction operator indicates that the interaction fragment
runs repeatedly. The number of times the fragment runs is determined by the minint and maxint parameters
of the operator. The syntax of the loop operator is loop (minint, maxint)
where maxint can also be infinity (*). After the minimum
number of iterations is satisfied, a Boolean expression is tested on each
pass. When the Boolean expression tests false, the loop ends. |