Oliver Mooney wrote:
Peter,
Thanks for pointing me in the right direction - I've derived a working
solution but it looks a bit ungainly to me. I unrolled one iteration
of the function to get the reversed list started and then had to
short-circuit the final recursion on the far end to account for the
list being reversed starting out one element shorter. Does that
technically mean that I'm recursing n-1 times, so it isn't the
envisaged solution?
fun {Convolute L1 L2}
fun {ConvoluteAcc L1 L2 Acc}
case L1 of H1|T1 then
case L2 of H2|T2 then
local H3 in
H3|_ = Acc
H1#H3|{ConvoluteAcc T1 T2 H2|Acc}
end
[] nil then
local H3 in
H3|_ = Acc
H1#H3|nil
end
end
end
end
Elem
in
case L2 of H|T then
{ConvoluteAcc L1 T H|Elem}
end
end
This code has a bug:
{Browse {Convolute [1 2 3] [a b c]}}
gives [1#a 2#b 3#c] instead of [1#c 2#b 3#a].
Hint: you need two arguments for the reversed list,
one to build it and one to decompose it. You can't
do both in one argument.
Peter
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