[Gambas-user] WHILE and AND: please explain me....

[Benoît Minisini]

> I'm working with this little piece of code, it's the Insertion Sort:
> 
> PUBLIC SUB InsertionSort(matrix AS String[])
> DIM i, j AS Integer
> DIM x AS String
> 
>   FOR i = 1 TO (matrix.Count - 1)
>     x = matrix[i]
>     j = i - 1
>     WHILE j >= 0 AND matrix[j] > x
>       matrix[j + 1] = matrix[j]
>       j -= 1
>     WEND
>     matrix[j + 1] = x
>   NEXT
> END
> 
> But I get an "Out of bound" error in the WHILE test, because j begins
> -1.
> 
> Usually (in other languages this is the behavior) the AND test checks
> the first condition, and if it is false then it checks the second one.
> OK... but shouldn't Gambas bypass the WHILE statement because j is
> negative?

AND is a logical operator in Gambas, and it evaluates both of its arguments.

You must write it this way:

  DO
    IF j < 0 OR IF matrix[j] <= x THEN BREAK
    matrix[j + 1] = matrix[j]
    j -= 1
  LOOP

Regards,

-- 
Benoît Minisini