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CyclicReadStream. Not in base Pharo.
I wish.
We have atWrap: but not the best.
Phil
On Mon, Dec 3, 2018 at 1:17 PM Richard O'Keefe wrote:
> "if I use do: this ends at the end of the array."
> True. But all that means is that you have to keen on using #do:.
>
> Processing an array repeatedly is as simple as
> [true] whileTrue: [
> anArray do: [:each |
> ...]]
>
> I had intended to twist this into
>
> [changes anySatisfy: [:change | ...]] whileFalse.
>
> However, in this case your second alternative has much to recommend it.
> The control flow is simple. There's no magic about it. It's an
> unusual setup, so no need to get fancy.
>
> seen := Set new.
> frequency := 0.
> found := false.
> i := changes size.
> [found] whileFalse: [
> i := i = changes size ifTrue: [1] ifFalse: [i+1].
> frequency := frequency + (changes at: i).
> found := seen includes: frequency.
> seen add: frequency].
>
> I like this better than what I had.
>
> If we _were_ to get fancy, then introducing a CyclicReadStream
> class and doing
> seen := Set new.
> frequency := 0.
> found := false.
> stream := CyclicReadStream on: self changes.
> [found] whileFalse: [
> frequency := frequency + stream next.
> found := seen includes: frequency.
> seen add: frequency].
> wouldn't shrink the code much. Oddly enough, I've encountered
> problems in previous Advent of Code exercises where CyclicReadStream
> would have been handy. But just for this case? No.
>
>
> On Tue, 4 Dec 2018 at 00:25, Roelof Wobben wrote:
>
>> hello Richard,
>>
>> Thanks, I figured that out already.
>> What I do not get is how to read the array multiple times.
>>
>> if I use do: this ends at the end of the array.
>>
>> Or I must use something as this :
>>
>> index := 0
>> if index > array length
>> index =: 1
>> else
>> index := index + 1
>>
>>
>> and then read the number with array at: index
>>
>> Roelof
>>
>>
>> Op 3-12-2018 om 10:08 schreef Richard O'Keefe:
>>
>> Roelof Wobben wrote
>> "I have to reread the file till the adding causes the same outcome as
>> we had already"
>> You have to process the *sequence of changes* repeatedly;
>> you DON't have to *reread the file*. Somebody already made this point.
>> Having read the changes into an array, you can iterate repeatedly over
>> that array.
>>
>> to find the first repeated frequency given a sequence of changes
>> make an empty Set to hold the sums that have been seen so far.
>> set the frequency to 0.
>> loop forever
>> for each change in the changes
>> increment the frequency by the change.
>> if the frequency is in the set
>> return the frequency
>>otherwise add the frequency to the set.
>>
>> partTwo: aFileName
>> Transcript print: (self firstRepeatedFrequency: (self changesFrom:
>> aFileName)); cr; flush.
>>
>> On Mon, 3 Dec 2018 at 19:31, Roelof Wobben wrote:
>>
>>> Thanks,
>>>
>>> For the second I have to take a good look.
>>>
>>> I have to reread the file till the adding causes the same outcome as we
>>> had already
>>>
>>> so for example if we have the sequence :
>>>
>>> +3, +3, +4, -2, -4
>>>
>>> it has as outcome :
>>>
>>> 3 6 10 8 4
>>>
>>> so no outcome is there a second time so we repeat the sequence
>>>
>>>
>>> 7 10
>>>
>>> the 10 shows up a second time so there we have our answer.
>>>
>>>
>>> Roelof
>>>
>>>
>>>
>>> Op 3-12-2018 om 03:45 schreef Richard O'Keefe:
>>>
>>> The key question is "what do you mean by improve"?
>>> I'd start by asking "what are you doing that you will still have to do in
>>> part 2, and what won't you do?" So looking at part 2, you will want to
>>> convert the lines to integers, and
>>> input := Array streamContents: [:lines |
>>> 'input.txt' asFileReference readStreamDo: [:in |
>>> [in atEnd] whileFalse: [lines nextPut: in nextLine asInteger]]].
>>> gives you a chunk of code you can use in both parts. So you might
>>> want to have
>>>
>>> Day1
>>> changesFrom: aFileName
>>> ^Array streamContents: [:changes |
>>> aFileName asFileReference readStreamDo: [:in |
>>> [in atEnd] whileFalse: [changes nextPut: in nextLine asInteger]]]
>>> partOne: aFileName
>>> ^(self changesFrom: aFileName) sum
>>> partTwo: aFileName
>>> ...
>>> The file name should not be wired in because you want some test files.
>>>
>>>
>>>
>>>
>>
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