on_receive.md

on_receive

Binds a function to the parent node, the function will be called each time the parent node "receives".

set l []
sequence
  on_receive (def msg \ push l 'a')
  push l 0
  push l 1
  push l 2

will result in the variable l holding [ 0, 'a', 1, 'a', 2, 'a' ].

set l []
sequence
  push l 0
  on_receive (def msg \ push l 'a')
  push l 1
  push l 2

will result in the variable l holding [ 0, 1, 'a', 2, 'a' ].

It's meant to play well with a cursor:

set l []
cursor
  on_receive (def \ break _ if l[-1] == 1)
  push l 0
  push l 1
  push l 2
push l 'z'

will result in the variable l holding [ 0, 1, 'z' ].

arguments to the on_receive function

msg and fcid (from child id) are passed to the function

set l []
cursor
  on_receive (def msg, fcid \ push l [ msg.from, fcid ])
  push l 0
  push l 1
  push l 2

will result in the variable l holding [ 0, [ '0_1_1', 1 ], 1, [ '0_1_2', 2 ], 2, [ '0_1_3', 3 ] ].

on_receive and on receive

A "lighter" notation is available (it's translated automatically to a on_receive):

set l []
cursor
  on receive
    push l $msg.from
    break _ if l.-1 == 1
  push l 0
  push l 1
  push l 2

Please note the $msg variable made available to the on receive block.

concurrence and on_receive

Please not that concurrence has its own on_receive with a slightly different behaviour.

• source
• on_receive spec