nested for loop incremenets by 1 but doesn't enter the loop block

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Hi, I have a function in a small project, This function contains a nested loop the outermost loop increments by 1 it satisfies the condition but it executes the loop body once. if i = 1 , j = 1 then x = 3 and y = 3 - I'm sure about these values using the debugger - but i becomes 2 then 3 without executing, it works only if I = 1.

C++

bool is_available_in_box(const short& num,const short& box_index)
{
    short place = get_location(box_index);
    short i = place / 10 , j = place % 10;
    short x = i + 2 , y = j + 2;
    for (i = i; i <= x; i++)
    {
        for (j = j; j <= y; j++)
        {
            if ( game[GAME_BOARD][i][j] == num )
            {
                return false;
            }
        }
    }
    return true;
}

Where is the problem ??

Thanks, Samuel.

Posted 1-Jul-15 8:35am

Samuel Shokry

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Comments

PIEBALDconsult 1-Jul-15 14:40pm

for (j = j ?

And probably better not to use for loops in that function anyway.

Sergey Alexandrovich Kryukov 1-Jul-15 16:31pm

1) What do you want to achieve? 2) use the debugger.
—SA

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CPallini · Accepted Answer · 2015-07-01T09:36:00

Solution 1

Self assignments (i=i; j=j;) as already noted by PIEBALDconsult, are useless.

In any case, your outer loop should be executed exactly three times, and for each of such iterations ~~the inner loop should be executed exactly three times~~.
[update]
As PIEBALDconsult pointed out j=j is a mistake (I overlooked it): at first outer loop iteration it is useless but harmless. Since second outer iteration, however, j=j is equivalent to j=y+1, preventing inner loop execution.
[/update]
However, at any iteration, if the condition

C++

game[GAME_BOARD][i][j] == num

is true then the loops are immediately exited due to the

C++

return false;

statement.

Posted 1-Jul-15 9:36am

CPallini

Updated 1-Jul-15 20:33pm

v2

Comments

PIEBALDconsult 1-Jul-15 16:16pm

Actually, the i=i is merely useless, whereas the j=j is even wronger than that.

Sergey Alexandrovich Kryukov 1-Jul-15 16:32pm

"Wronger" is great concept. :-)
—SA

Richard Deeming 1-Jul-15 16:38pm

That sounds like the answer to me! :)

CPallini 2-Jul-15 2:27am

Yes, you are right, I overlooked that. Thanks.

Sergey Alexandrovich Kryukov 1-Jul-15 16:32pm

5ed.
—SA

nested for loop incremenets by 1 but doesn't enter the loop block

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nested for loop incremenets by 1 but doesn't enter the loop block

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