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copied!<p>You're almost there. While I agree with @koodawg that adding a counter and a running total is another solution for this problem, having those in your code will complicate it more than it needs to be.</p> <p>First, I have a few comments about your code. You must remove the unnecessary parens. <code>hd(numbers)</code> is same as <code>hd numbers</code> and <code>(hd(tl numbers))</code> is equal to <code>hd(tl numbers)</code>. So your <code>(hd(numbers)+(hd(tl numbers)))</code> could be simplified to <code>(hd numbers + hd(tl numbers))</code>. Also, you can combine <code>if null numbers</code> and <code>if hd(numbers) > sum</code> in a single condition for code brevity since they yield the same result: <code>0</code>.</p> <p>I'll try to explain how code works and I hope you'll get the idea where you have to amend your code.</p> <p>Using your example, <code>index(10, [1,2,3,4,5,6,7])</code>, <strong>your code execution will be like this:</strong></p> <p>1) </p> <pre><code> fun index(10, [1,2,3,4,5,6,7]) = if 1 > 10 then 0 else 1 + (10, [1 + 2] append to [2,3,4,5,6,7]) </code></pre> <p><strong>new list:</strong> [3,2,3,4,5,6,7] <br /> <strong>result:</strong> 1 </p> <p>2) </p> <pre><code> fun index(10, [3,2,3,4,5,6,7]) = if 3 > 10 then 0 else 1 + (10, [3 + 2] append to [2,3,4,5,6,7]) </code></pre> <p><strong>new list:</strong> [5,2,3,4,5,6,7] <br /> <strong>result:</strong> 1 </p> <p>3) </p> <pre><code> fun index(10, [5,2,3,4,5,6,7]) = if 5 > 10 then 0 else 1 + (10, [5 + 2] append to [2,3,4,5,6,7]) </code></pre> <p><strong>new list:</strong> [7,2,3,4,5,6,7] <br /> <strong>result:</strong> 1 </p> <p>4) </p> <pre><code> fun index(10, [7,2,3,4,5,6,7]) = if 7 > 10 then 0 else 1 + (10, [7 + 2] append to [2,3,4,5,6,7]) </code></pre> <p><strong>new list:</strong> [9,2,3,4,5,6,7] <br /> <strong>result:</strong> 1 </p> <p>5) </p> <pre><code> fun index(10, [9,2,3,4,5,6,7]) = if 9 > 10 then 0 else 1 + (10, [9 + 2] append to [2,3,4,5,6,7]) </code></pre> <p><strong>new list:</strong> [11,2,3,4,5,6,7] <br /> <strong>result:</strong> 1 </p> <p>6) </p> <pre><code> fun index(10, [11,2,3,4,5,6,7]) = if 11 > 10 then 0 </code></pre> <p><strong>result:</strong> 0 </p> <p>To sum all results: 1 + 1 + 1 + 1 + 1 + 0 = 5 (just like what you said that your function adds 2 to the expected result)</p> <p><strong>The correct code must behave like this:</strong> </p> <p>1) </p> <pre><code> fun index(10, [1,2,3,4,5,6,7]) = if 1 > 10 then 0 else 1 + (10, [1 + 2] append to [3,4,5,6,7]) </code></pre> <p><strong>new list:</strong> [3,3,4,5,6,7] <br /> <strong>result:</strong> 1 </p> <p>2) </p> <pre><code> fun index(10, [3,3,4,5,6,7]) = if 3 > 10 then 0 else 1 + (10, [3 + 3] append to [4,5,6,7]) </code></pre> <p><strong>new list:</strong> [6,4,5,6,7] <br /> <strong>result:</strong> 1 </p> <p>3) </p> <pre><code> fun index(10, [6,4,5,6,7]) = if 6 > 10 then 0 else 1 + (10, [6 + 4] append to [5,6,7]) </code></pre> <p><strong>new list:</strong> [10,5,6,7] <br /> <strong>result:</strong> 1 </p> <p>4) </p> <pre><code> fun index(10, [10,5,6,7]) = if 10 > 10 then 0 </code></pre> <p><strong>result:</strong> 0 </p> <p>To sum all results: 1 + 1 + 1 + 0 = 3 which is the expected answer. </p> <p><strong>HINT:</strong> You always make sure that the new list your function is processing must be smaller than the previous list/original list. </p> <p>I hope I explained clearly why your code isn't working. I didn't include the code because I know this is a homework for an online class.</p>

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