Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>For solutions, see <a href="http://clc-wiki.net/wiki/K%26R2_solutions:Chapter_5:Exercise_5" rel="nofollow noreferrer">CLC Wiki page</a>.</p> <p>Now some comments about your code:</p> <p>For <code>strncmp</code>:</p> <pre><code>if(strlen(s) == strlen(t)) { </code></pre> <p>You don't need this check. <code>strlen()</code> traverses the string, so you are going to process the strings twice if the lengths are equal. This can get expensive. In general, low-level functions like these, which can be called a lot in any program should be efficient (although premature optimization is the root of all evil!). Also, you're calling <code>strlen()</code> again for both the strings if the lengths aren't equal. In addition to being expensive, it is wrong too, but we will come to that later. About your <code>while</code> loop:</p> <pre><code>while(*s == *t &amp;&amp; *s &amp;&amp; n) n--, s++, t++; </code></pre> <p>Why abuse the comma operator? I would simplify and write the above as (untested, after all, this is an exercise <em>you</em> are solving!):</p> <pre><code>while (*s &amp;&amp; *t &amp;&amp; *s == *t &amp;&amp; n--) { s++; t++; } if (!n) return 0; else return *s - *t; </code></pre> <p>Your return values are wrong. <code>strncmp()</code> should return 0, less-than 0, or greater-than 0 depending upon whether the first <code>n</code> characters of the first string compare equal to, less than, or greater than (lexicographically) the second string.</p> <p>Similarly, you should change your <code>strncpy()</code> and <code>strncat2()</code> functions. I haven't looked at those two in detail, but since this is an exercise, you probably want to make the changes yourself anyway.</p>
    singulars
    1. This table or related slice is empty.
    1. POHow to write C string functions: strncpy , strncat , and strncmp
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USAlok Singhal
    1. USAlok Singhal
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. COLexicographicaly - does this means subtracting their ASCII values?
      singulars
      1. PO
      1. USTool
    2. CONo, ASCII doesn't come in the picture here. If a character set is such that `'a'` > `'b'`, then `strcmp("a", "b")` will return a number greater than 0, which might be surprising. Lexicographic order is "dictionary order", but using platform-specific encoding for characters. If you need to rely on the relative ordering of strings, `strcmp()` might not be the best way to do it (unless you're sure you're on "sane" systems!).
      singulars
      1. PO
      1. USAlok Singhal
    3. COIt is common to do "`return *s - *t;`" like I have for string comparison functions, but the standard only specifies the return values as 0, >0, and <0, so one could return any values satisfying that criterion.
      singulars
      1. PO
      1. USAlok Singhal
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload