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1 \begin{isabelle}% |
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2 % |
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3 \begin{isamarkuptext}% |
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4 \noindent In Exercise~\ref{ex:Tree} we defined a function |
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5 \isa{flatten} from trees to lists. The straightforward version of |
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6 \isa{flatten} is based on \isa{\at} and is thus, like \isa{rev}, quadratic. |
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7 A linear time version of \isa{flatten} again reqires an extra |
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8 argument, the accumulator:% |
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9 \end{isamarkuptext}% |
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10 \isacommand{consts}~flatten2~::~{"}'a~tree~=>~'a~list~=>~'a~list{"}% |
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11 \begin{isamarkuptext}% |
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12 \noindent Define \isa{flatten2} and prove% |
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13 \end{isamarkuptext}% |
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14 \isacommand{lemma}~{"}flatten2~t~[]~=~flatten~t{"}\end{isabelle}% |
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15 %%% Local Variables: |
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16 %%% mode: latex |
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17 %%% TeX-master: "root" |
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18 %%% End: |