Simpson's 1/3 rule on the 50g

[Juan14]

This program uses GETI to get trough each element of the list, flag -64 is checked in the WHILE loop, it gets set when the index reach the end of the list. In the loop, a 4 or 2 is generated with the help of MOD. The program requires h in level 2: and the list of values in level 1:

«
1 GETI UNROT
WHILE GETI -64 FC?
REPEAT
OVER 2 MOD 2 * 2 + * 4 ROLL + UNROT
END NIP NIP + * 3 /
»