RosettaCodeData/Task/Van-Eck-sequence/CLU/van-eck-sequence.clu

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% Generate the first N elements of the Van Eck sequence
eck = proc (n: int) returns (array[int])
ai = array[int]
e: ai := ai$fill(0, n, 0)
for i: int in int$from_to(ai$low(e), ai$high(e)-1) do
for j: int in int$from_to_by(i-1, ai$low(e), -1) do
if e[i] = e[j] then
e[i+1] := i-j
break
end
end
end
return(e)
end eck
% Show 0..9 and 990..999
start_up = proc ()
po: stream := stream$primary_output()
e: array[int] := eck(1000)
stream$puts(po, " 0 - 9: ")
for i: int in int$from_to(0,9) do
stream$putright(po, int$unparse(e[i]), 4)
end
stream$puts(po, "\n990 - 999: ")
for i: int in int$from_to(990,999) do
stream$putright(po, int$unparse(e[i]), 4)
end
stream$putl(po, "")
end start_up