Could this be a infinite loop?

Could this be a infinite loop? - Printable Version

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+--- Thread: Could this be a infinite loop? (/showthread.php?tid=624635)

Could this be a infinite loop? - iLearner - 20.12.2016

PHP код:



    if (strcmp(tmp1, "color", true) == 0)

    {

        new color, colorstr[30];

        if (!AdminCheck(playerid, 4)) return SendClientMessage(playerid, ERRORCOLOR, "Usage: /gang [create|invite|kick|join|quit|setrank]");

        if (!sscanf(tmp2, "is[30]", id, colorstr))

        {

            if (strlen(colorstr) != 6) return SendClientMessage(playerid, ERRORCOLOR, "Invalid color code.");

            strcat(tmp2, "FF");

        }

        if (sscanf(tmp2, "ix", id, color)) return SendClientMessage(playerid, ERRORCOLOR, "Usage: /gang color [gangid] [colorcode]");

        format(tmp1, sizeof(tmp1), "SELECT * FROM `Gangs` WHERE `id` = %d", id);

        result = db_query(Database, tmp1);

        if (db_num_rows(result) == 0)

        {

            db_free_result(result);

               return SendClientMessage(playerid, ERRORCOLOR, "Invalid gangid.");

        }

        db_free_result(result);

        format(tmp1, sizeof(tmp1), "UPDATE `Gangs` SET `color` = %d WHERE `id` = %d", color, id);

        db_query(Database, tmp1);

        format(tmp1, sizeof(tmp1), "SELECT * FROM `Gangmembers` WHERE `gangid` = %d", id);

        result = db_query(Database, tmp1);

        new rows = db_num_rows(result);

        while (0 < rows)

        {

            db_get_field_assoc(result, "userid", tmp1, sizeof(tmp1));

            new pid = GetPlayerID(GetNameFromUserID(strval(tmp1)));

            if (IsPlayerConnected(pid)) { SetPlayerColor(pid, color); pcolor[pid] = color; }

            db_next_row(result);

            rows--;

        }

        db_free_result(result);

        SendMessageToGang(id, "{8B72F2}Your gang color has changed.");

        return 1;

    }

I failed to understand the "0<rows"

Re: Could this be a infinite loop? - Lordzy - 20.12.2016

Just checked the loop part and no, it's not an infinite loop. It's just clear mathematical logic. (0 < rows) is equal to (rows > 0). Here, when the number of rows retrieved are greater than zero, the loop runs until the 'rows' variable becomes zero or less. That's why you can see "rows--" statement under the loop. For instance, you can consider this:

pawn Код:

new rows = db_num_rows(result); //Suppose that rows is now 3. (rows = 3)
        while (0 < rows) //(0 is of course less than 3, so the loop runs until 0 < 0 occurs.)
        {
            db_get_field_assoc(result, "userid", tmp1, sizeof(tmp1));
            new pid = GetPlayerID(GetNameFromUserID(strval(tmp1)));
            if (IsPlayerConnected(pid)) { SetPlayerColor(pid, color); pcolor[pid] = color; }
            db_next_row(result);
            rows--; //The value of rows keeps on decreasing.
        }

Re: Could this be a infinite loop? - Vince - 20.12.2016

Quote:

Originally Posted by Lordzy

It's just clear mathematical logic. (0 < rows) is equal to (rows > 0).

"Clear". Right. Where possible I keep variables to the left and constants to the right because "do something while rows are greater than zero" sounds much better in my head than "do something while zero is less than rows".