hi all, I am trying to read more example in FunC:

since the template for payment channel here has these two lines I can't figure out

• how it works
• why we need it here

(slice -> int) cast_to_S2I(cont c) asm "NOP";
;; (slice, int) load_coins(slice s) asm( -> 1 0) "LDVARUINT16";
;; builder store_coins(builder b, int x) asm "STVARINT16";
forall X, Y, Z -> tuple t_triple(X x, Y y, Z z) asm "TRIPLE";

https://github.com/ton-blockchain/payment-channels/blob/e605580c3fb1feb22d80be9a0cddfcd05671c347/func/async-channel.func#L30

Can anyone answer this? and explaind those 2 for?