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    <h2>for loop condition</h2> <pre><code>i["]&lt;i;++i){--i;}"] </code></pre> <p>This expression takes advantage of the fact that array indexing is commutative in C. It is equivalent to.</p> <pre><code>"]&lt;i;++i){--i;}"[i] </code></pre> <p>So the loop will terminate when the character at position <code>i</code> is <code>\0</code>, i.e., at the end of the string, which is 14 characters long (which happens to be the same length as "hello, world!\n"). So the <code>for</code> loop condition can be rewritten as:</p> <pre><code>i != 14 </code></pre> <h2>character arithmetic</h2> <pre><code>read('-' - '-', i++ + "hello, world!\n", '/' / '/') </code></pre> <p><code>char</code> is an integer type, and thus:</p> <ul> <li><code>'-' - '-'</code> is 0</li> <li><p><code>'/' / '/'</code> is 1</p> <p>read(0, i++ + "hello, world!\n", 1)</p></li> </ul> <hr> <p>After fixing all the compiler warnings (like implicit int to pointer conversion), and simplifying the things mentioned above, the code becomes:</p> <pre><code>#include &lt;unistd.h&gt; int i = 0; void read2(int, char*, int); int main() { while (i != 14) { read2(0, i++ + "hello, world!\n", 1); } return 0; } void read2(int j, char* i, int p) { write(j / p + p, i-- - j, 1); } </code></pre> <p>(I renamed <code>read</code> to <code>read2</code> to avoid conflicting with the Unix <code>read</code> function.)</p> <p>Note that the <code>j</code> and <code>p</code> arguments to <code>read2</code> are unneeded, as the function is always called with j=0 and p=1.</p> <pre><code>#include &lt;unistd.h&gt; int i = 0; void read2(char*); int main() { while (i != 14) { read2(i++ + "hello, world!\n"); } return 0; } void read2(char* i) { write(1, i--, 1); } </code></pre> <p>The call <code>write(1, i--, 1)</code> writes 1 character from <code>i</code> to file descriptor 1 (stdout). And the postdecrement is superfluous because this <code>i</code> is a local variable never referenced again. So this function is equivalent to <code>putchar(*i)</code>.</p> <p>Inlining the <code>read2</code> function within the main loop gives</p> <pre><code>#include &lt;stdio.h&gt; int i = 0; int main() { while (i != 14) { putchar(*(i++ + "hello, world!\n")); } return 0; } </code></pre> <p>for which the meaning is obvious.</p>
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