Receive block

A receive expression is used to wait for a signal on the current process.

A signal MUST be a tuple containing 3 elements:

• the type of signal, as an atom (@message or @exited)
• the PID of the process from which the signal originated
• the payload of the signal

Syntax

receive_expression
  = "receive" "{" pattern_matching_clause ("," pattern_matching_clause)* ","? "}"
  receive_after_expression?

receive_after_expression
  = "after" expression "{" (expression ";")+ "}"

Example

receive {
  (@message, proc_id, msg) -> {
    # ...
  },
  (@exited, proc_id, reason) -> {
    # ...
  },
}
after 1000 {
  # ...
};

Semantics

A receive expression MUST block until a signal is received.

The receive expression MUST evaluate to the value the matching clause evaluates to.

If no clause matched, an exception MUST be thrown. The value of that exception is defined by the implementation.

If present, the after part of the receive expression MUST add a timeout, after which we no longer wait for a signal.

The expression of the after part MUST evaluate to an integer, which is the timeout in milliseconds. If it does not evaluate to an integer, an exception MUST be thrown. The value of that exception is defined by the implementation.

After the timeout, the body of the after part MUST be evaluated. In such case, the receive expression MUST evaluate to the value the body evaluates to.

The body of the after part MUST create a new scope.