Hofstadter Figure-Figure sequences: Difference between revisions
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(Factor solution) |
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true</pre> |
true</pre> |
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=={{header|Factor}}== |
=={{header|Factor}}== |
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The core of this algorithm builds up a list of S and R one at a time. The solution to task 1 follows. |
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<lang factor>: next ( s r -- news newr ) |
<lang factor>: next ( s r -- news newr ) |
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2dup [ last ] bi@ + suffix |
2dup [ last ] bi@ + suffix |
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dup [ |
dup [ |
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[ dup last 1 + dup ] dip member? [ 1 + ] when suffix |
[ dup last 1 + dup ] dip member? [ 1 + ] when suffix |
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] dip ; |
] dip ; |
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: SR ( n -- S(n) R(n) ) |
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Tests: |
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1 - |
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[ { 2 } { 1 } ] dip [ next ] times |
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[ last ] bi@ ; |
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: ffs ( n -- S(n) ) SR drop ; |
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: ffr ( n -- R(n) ) SR nip ; |
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</lang> |
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For tasks 3 and 4 we ignore the functions <code>ffs</code> and <code>ffr</code> and simply use <code>next</code>. |
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<lang factor>( scratchpad ) { 2 } { 1 } 1000 [ next ] times ! Generate the first 1000 values of S and R |
<lang factor>( scratchpad ) { 2 } { 1 } 1000 [ next ] times ! Generate the first 1000 values of S and R |
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