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Top Forums Programming C Beginner Looking For Suggestions Post 302302617 by deckard on Tuesday 31st of March 2009 12:40:42 PM
Old 03-31-2009
Question C Beginner Looking For Suggestions

A few weeks ago at the recommendation of people I trust, I bought and started reading Kernighan and Ritchie's (K&R) C Programming Language. For one thing, it's damn thin compared to the O'Reilly Practical C I just finished last month. It covers generally the same stuff but in a much more efficient manner. Of course, what do I know? I'm only on chapter 1 and I'm taking K&R's advice and pausing my reading to work through the programming problems in the chapter. One thing that's kind of frustrating to me is that I ran into a problem that seems like it could have an elegant solution, but I've not come up with one. Problem 1-9 which says:

"Write a program to copy its input to its output, replacing each string of one or more blanks by a single blank".

At first I tried coming up with my own code from scratch and wound up with some freakish binary that spit out unprintable characters (probably a mix up in data types). So I started over and entered their file copying program example (1.5.1) from page 16. Then I thought about how to modify it. Here is what I came up with:

Code:
#include <stdio.h>

int main()
{
  int c, space;

  space = 0;
  c = getchar();

  while (c != EOF) {
  if (c == 32 && space == 1)
    /* do nothing */;
  else if (c != ' ') {
    space = 0;
    putchar(c);}
  else if (c == ' ') {
    space = 1;
    putchar(c);}
    
    c = getchar();
  }
}

(NOTE: I used 32 for space in the first if conditional while testing and didn't switch it back to c == ' '.)

The compiled program works on the most basic level, but I'm sure it's bug ridden and the wrong input will make it barf. Since it does what it's supposed to, I've moved on. But I'm strangely bothered since I *KNOW* there has to be a better way than a bunch of serial if conditionals. I get this nagging feeling that I could do it shorter and with fewer checks.

But I just couldn't do it. Anyone else see where I'm totally off? This is definitely beginner style code and I admit as much. But I was pretty bad in the beginning with Bash too (I had a full page script in 2001 to generate MP3 playlists by traversing directories. Today I have a two liner using the 'find' command), so I think there is hope for my dream of one day being fluent at C. Anyone have any suggestions about my above code? Where could my thinking be improved?

I'll also say that I have a lot of trouble thinking in parallel, but it seems that that is how the best coders think. My code has always been serial in DOS BAT files, CMD, Bash, Perl and now C. Any tips on changing that way of seeing things? Also, let me know if this isn't the right place to post this.

NOTE: I know there's an "answer book" for this book. But I want to do it the "hard way" first and then when I'm done I'll compare my answers with the ones in the answer book.
 

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MYSQL_QUERY(3)								 1							    MYSQL_QUERY(3)

mysql_query - Send a MySQL query

SYNOPSIS
Warning This extension is deprecated as of PHP 5.5.0, and will be removed in the future. Instead, the MySQLi or PDO_MySQL extension should be used. See also MySQL: choosing an API guide and related FAQ for more information. Alternatives to this function include: omysqli_query(3) o PDO::query mixed mysql_query (string $query, [resource $link_identifier = NULL]) DESCRIPTION
mysql_query(3) sends a unique query (multiple queries are not supported) to the currently active database on the server that's associated with the specified $link_identifier. o $query - An SQL query The query string should not end with a semicolon. Data inside the query should be properly escaped. o $ link_identifier -The MySQL connection. If the link identifier is not specified, the last link opened by mysql_connect(3) is assumed. If no such link is found, it will try to create one as if mysql_connect(3) was called with no arguments. If no connection is found or established, an E_WARNING level error is generated. For SELECT, SHOW, DESCRIBE, EXPLAIN and other statements returning resultset, mysql_query(3) returns a resource on success, or FALSE on error. For other type of SQL statements, INSERT, UPDATE, DELETE, DROP, etc, mysql_query(3) returns TRUE on success or FALSE on error. The returned result resource should be passed to mysql_fetch_array(3), and other functions for dealing with result tables, to access the returned data. Use mysql_num_rows(3) to find out how many rows were returned for a SELECT statement or mysql_affected_rows(3) to find out how many rows were affected by a DELETE, INSERT, REPLACE, or UPDATE statement. mysql_query(3) will also fail and return FALSE if the user does not have permission to access the table(s) referenced by the query. Example #1 Invalid Query The following query is syntactically invalid, so mysql_query(3) fails and returns FALSE. <?php $result = mysql_query('SELECT * WHERE 1=1'); if (!$result) { die('Invalid query: ' . mysql_error()); } ?> Example #2 Valid Query The following query is valid, so mysql_query(3) returns a resource. <?php // This could be supplied by a user, for example $firstname = 'fred'; $lastname = 'fox'; // Formulate Query // This is the best way to perform an SQL query // For more examples, see mysql_real_escape_string() $query = sprintf("SELECT firstname, lastname, address, age FROM friends WHERE firstname='%s' AND lastname='%s'", mysql_real_escape_string($firstname), mysql_real_escape_string($lastname)); // Perform Query $result = mysql_query($query); // Check result // This shows the actual query sent to MySQL, and the error. Useful for debugging. if (!$result) { $message = 'Invalid query: ' . mysql_error() . " "; $message .= 'Whole query: ' . $query; die($message); } // Use result // Attempting to print $result won't allow access to information in the resource // One of the mysql result functions must be used // See also mysql_result(), mysql_fetch_array(), mysql_fetch_row(), etc. while ($row = mysql_fetch_assoc($result)) { echo $row['firstname']; echo $row['lastname']; echo $row['address']; echo $row['age']; } // Free the resources associated with the result set // This is done automatically at the end of the script mysql_free_result($result); ?> mysql_connect(3), mysql_error(3), mysql_real_escape_string(3), mysql_result(3), mysql_fetch_assoc(3), mysql_unbuffered_query(3). PHP Documentation Group MYSQL_QUERY(3)
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