>> > I guess that the cost of returning function is compensated by proper tail
>> > recursion in the "chain" case, and that x1.09 slowdown of the "plain_chain"
>> > case is that cost itself.
Here are the results of somewhat related benchmark on the cost of return (code attached).
lua
-------------------------------------------------------------------
name | rel | abs s / iter = us (1e-6 s) / iter
-------------------------------------------------------------------
no_ret | 1.0000 | 167.89 / 1000000000 = 0.167890 us
ret_nil | 1.0124 | 169.97 / 1000000000 = 0.169970 us
ret_true | 1.0425 | 175.02 / 1000000000 = 0.175020 us
ret_self | 1.0643 | 178.68 / 1000000000 = 0.178680 us
luajit -O
-------------------------------------------------------------------
name | rel | abs s / iter = us (1e-6 s) / iter
-------------------------------------------------------------------
no_ret | 1.0000 | 24.37 / 1000000000 = 0.024370 us
ret_true | 1.0484 | 25.55 / 1000000000 = 0.025550 us
ret_self | 1.0513 | 25.62 / 1000000000 = 0.025620 us
ret_nil | 1.0570 | 25.76 / 1000000000 = 0.025760 us
