Noob Question - slicing

> On 6 Mar 2019, at 13:48, Richard O'Keefe <[hidden email]> wrote:
>
> As someone else already pointed out, the standard way to copy
> part of any array-like sequence is
>    aSequence copyFrom: firstIncludedIndex to: lastIncludedIndex
>
> How could you have found this by yourself?
>
> From the background, either
>   Click-select Tools-select Playground
> or hold Ctrl down while typing OW (for Open Workspace).
> In the new Playground/workspace, type
>   String
> then Ctrl-B.  You now have a five-pane browser open on
> String.
>
> About half way down the third panel on the top you will see
>   converting
>   copying
>   displaying
> Click on copying.
>
> Guess what?  You WON'T see anything that looks relevant!
> Maybe it's in an ancestral class.  So look at the buttons
> under the top row of panes:
>  All packages  Scoped view | Flat Hier | Inst side Class side | ...
> Hier looks promising.  Click it.
>
> Now in the second pane you will see
> ProtoObject
>   Object
>     Collection
>       SequenceableCollection
>         ArrayedCollection
>           String
>             ...
> Select the parent class, ArrayedCollection.
> Nope, nothing promising there either!
> Select the grandparent class, SequenceableCollection.
> And now the 'copying' method category has quite a few
> potentially interesting methods, including #copyFrom:to:.
>
> There are four other related methods that I would argue
> are in the wrong category:
>   allButFirst
>   allButFirst: count
>   allButLast
>   allButLast: count
> are in the 'accessing' category.
>
> If you want something a bit more flexible,
> you could add
>     drop: d take: t
>       "Discard the first |d| elements of the receiver if d >= 0.
>        Discard the last  |d| elements of the receiver if d <= 0.
>        Return  the first |t| elements of the result   if t >= 0.
>        Return  the last  |t| elements of the result   if t <= 0.
>        The result is the same kind of collection as the receiver."
>       |lb ub n|
>       n := self size.
>       d abs >= n ifTrue: [^self copyEmpty].
>       d < 0
>         ifTrue:  [lb := 1.   ub := n + d]
>         ifFalse: [lb := d+1. ub := n].
>       ub - lb + 1 <= t abs ifFalse: [
>         t < 0
>           ifTrue:  [lb := ub + t + 1]
>           ifFalse: [ub := lb + t - 1]].
>       ^self copyFrom: lb to: ub
>
> Now I would like to suggest that you not use anything like this
> *directly*.  Go back to the Playground, and evaluate
>
>   String with: (Character codePoint: 256) <Ctrl-P>
>
> The answer is 'Ā'. Pharo supports Unicode.  Now try
>
>   String with: $A with: (Character codePoint: 16r0304)
>
> In Pharo, the result looks like A followed by a separate
> macron, but when it's pasted into HTML it displays
> correctly as 'Ā'.  Pharo doesn't *quite* support Unicode.
> If it did, the two strings with different lengths and no
> codepoint in common would display exactly the same.
>
> The Unicode standard finds it necessary to distinguish
> between characters, glyphs, graphemes, grapheme clusters,
> codepoints, and a couple of other things.  A Smalltalk
> String is a sequence of *codepoints*, not a sequence of
> "characters".  There is no upper bound on the number of
> codepoints that may be needed to encode one "character"
> as the end user sees it, and from there on it gets
> *complicated*.
>
> For over 20 years, it hasn't really made sense to think
> of a string as a simply indexed sequence of characters.
> Integer indices are a useful implementation-level detail
> for remembering bounds from some "higher level" matching
> technique, but are much less useful than you might expect.
>
>
>
>
>
>
>
> On Wed, 6 Mar 2019 at 12:00, Craig Johnson <[hidden email]> wrote:
> Hi All,
>
>  
>
> I was trying to figure an elegant way to slice strings (Python style), and came up empty.
>
>  
>
> What is the simplest way to copy characters between positions 4 and 8 from a string in Pharo?
>
>  
>
> Craig
>