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onSimilar to an interface, in a component the on defines which
trigger is to be handled. Component triggers, however, belong to
a port and carry formal parameters:
on ::= ("on" triggers ":" statement)
| ("on" illegal-triggers ":" illegal)
triggers ::= trigger ("," trigger)*
trigger ::= port-name "." event-name "(" formal-list? ")"
formal-list ::= formal ("," formal)*
formal ::= identifier | (identifier formal-binding)
statement ::= declarative-statement | imperative-statement | illegal
imperative-statement
::= action | assign | call | if | reply | return | variable
| imperative-compound
| empty-statement
illegal ::= "illegal"
imperative-compound
::= "{" (imperative-statement ";")* "}"
empty-statement
::=
illegal-triggers
::= illegal-trigger ("," illegal-trigger)*
illegal-trigger
::= port-name "." event-name
The formal-list to be used is defined by the parameters of the
event definition in the interface. Their relation is position-based.
Formal parameters may introduce another name than specified in the
event definition in the interface.
For example:
on p.hello (greeting): w.hello (greeting); on p.cruel, r.hello: illegal; // Note this is optional since 2.14.0.
When two or more imperative statements are specified for a certain trigger, the component is said to be non-deterministic. For example:
on p.hello (): w.hello (); on p.hello (): ;
non-determinism in components is not allowed and will lead to a verification error (See Verification Checks and Errors).
The formal-binding is a feature for blocking,
See Formal Binding.