Tutorial creates confusion about slices
Michael Bentley
michael at jedimindworks.com
Mon Apr 23 10:13:07 EDT 2007
On Apr 23, 2007, at 7:38 AM, Antoon Pardon wrote:
> The following is part of the explanation on slices in the
> tutorial:
>
> The best way to remember how slices work is to think of the indices as
> pointing between characters, with the left edge of the first character
> numbered 0. Then the right edge of the last character of a string of n
> characters has index n, for example:
>
> +---+---+---+---+---+
> | H | e | l | p | A |
> +---+---+---+---+---+
> 0 1 2 3 4 5
> -5 -4 -3 -2 -1
>
> This is all very well with a simple slice like:
>
> "HelpA"[2:4] => "lp"
>
>
> But it give the wrong idea when using the following extended slice:
>
> "HelpA"[4:2:-1] => "Ap"
>
> So this doesn't result in the reverse of the previous expression while
> the explanation above suggest it does.
>
>
> So I suggest to drop this.
But 'drop' means to let or make (something) fall vertically... :-)
At that point in the tutorial, step values had not been discussed.
Just a bit lower down on the page you'll find a link to 'Sequence
Types' where you'll find an explanation of stepping you'll perhaps
find more satisfactory.
hth,
Michael
---
"Those who don't understand UNIX are condemned to reinvent it,
poorly." --Henry Spencer
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