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    <p>As @WorBlux pointed out, you have some parenthesis problems. Besides that, I have a couple of tips:</p> <ul> <li>It's a bit clearer if you use nested <code>if</code>s to separate conditions</li> <li>Your conditions are not correct, the equality cases are missing</li> <li>If the conditions are right, it won't be necessary to have a catch-all <code>else</code> case</li> <li>You should declare a helper procedure for performing the actual squared sum</li> </ul> <p>This is what I mean:</p> <pre><code>(define (sumsq x y) (+ (* x x) (* y y))) (define (toptwosq a b c) (if (&gt;= a b) (if (&gt;= b c) (sumsq a b) (sumsq a c)) (if (&gt;= a c) (sumsq b a) (sumsq b c)))) </code></pre> <p>The same code can be written as follows using <code>cond</code>, notice how to correctly express the conditions in such a way that all cases are covered:</p> <pre><code>(define (toptwosq a b c) (cond ((and (&gt;= a b) (&gt;= b c)) (sumsq a b)) ((and (&gt;= a b) (&lt; b c)) (sumsq a c)) ((and (&lt; a b) (&gt;= a c)) (sumsq b a)) ((and (&lt; a b) (&lt; a c)) (sumsq b c)))) </code></pre> <p>The last condition can be replaced with an <code>else</code>. It's not a "catch-all", we're certain that at this point no more cases remain to be considered:</p> <pre><code>(define (toptwosq a b c) (cond ((and (&gt;= a b) (&gt;= b c)) (sumsq a b)) ((and (&gt;= a b) (&lt; b c)) (sumsq a c)) ((and (&lt; a b) (&gt;= a c)) (sumsq b a)) (else (sumsq b c)))) </code></pre> <p>And finally, if we're smart we can get rid of one case (the first and third cases are the same) and simplify the conditions even more:</p> <pre><code>(define (toptwosq a b c) (cond ((or (&gt;= a b c) (and (&gt;= a c) (&gt; b a))) (sumsq a b)) ((and (&gt;= a b) (&gt; c b)) (sumsq a c)) (else (sumsq b c)))) </code></pre>
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    1. POWhy won't my solution to SICP Exercise 1.3 work?
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    1. USÓscar López
    1. USÓscar López
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    1. COWhy not make the second level if's a procedure you can use in both branches?
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    2. COIt's possible, but it'll make the procedure harder to understand. I'll leave it as it is :)
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      1. USÓscar López
    3. COI like your nested ifs code much better: clear, self-evident, optimal: +1. --- The new `cond` codes have repeated tests, yikes. :)
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