This is a signals and slots library for nim.
sling is around 10x slower than traditional callbacks, which is the same speed as Qt's signal and slots library. A signal callback takes around 2ns, which a C callback version will take around 0.2ns overall, not much to worry about.
import sling
# The 'slot' keyword is just a typedef of 'void'.
# A slot needs to have a 'void' return value, so
# just use the 'slot' keyword for simplicity and style.
# Currently only 1 parameter value is supported in a slot, I will look more into this.
proc callback( i: int ): slot =
echo( "callback received: ", i )
var sig = signal[int]()
sig.connect( callback )
sig.connect( proc( i: int ): slot =
echo( "lambda recieved: ", i ) )
sig.emit( 200 ) # will print 'callback recieved 200' and 'lambda recieved 200'
# disconnect all callbacks
sig.clear()