Hofstadter Q sequence: Difference between revisions
Added Lua version
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</pre>
=={{header|Lua}}==
Here, the whole sequence up to the 100,000th term is generated for the first task, so this is where we risk hitting the recursion limit. As it happens, we do not. The function is called using 'pcall' so that any error would be caught. By increasing the argument on line 19 from 1e5 to 1e8, we can cause LuaJIT to run out of memory, but that is not necessary for this task.
<syntaxhighlight lang="lua">function hofstadter (limit)
local Q = {1, 1}
for n = 3, limit do
Q[n] = Q[n - Q[n - 1]] + Q[n - Q[n - 2]]
end
return Q
end
function countDescents (t)
local count = 0
for i = 2, #t do
if t[i] < t[i - 1] then
count = count + 1
end
end
return count
end
local noError, hofSeq = pcall(hofstadter, 1e5)
if noError == false then
print("The sequence could not be calculated up to the specified limit.")
os.exit()
end
for i = 1, 10 do
io.write(hofSeq[i] .. " ")
end
print("\n" .. hofSeq[1000])
print(countDescents(hofSeq))</syntaxhighlight>
{{out}}
<pre>1 1 2 3 3 4 5 5 6 6
502
49798</pre>
=={{header|MAD}}==
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