binary-search: use generics #868

FridaTveit · 2017-10-06T12:49:49Z

The binary-search tests force the practitioner to generify the class
but only one type (integer) was actually being used in the tests.
This should be changed so that more than one type is actually used, to
make it more clear that generics are necessary and to demonstrate how
generics is used.

As discussed in #230, move linked-list to one of the last difficulty 6
exercises, so that binary-seach is the first exercise that introduces
generics.

Add a hint to the binary-search exercise to explain generics as this
is now the first exercise to require it.

Should hopefully fix the binary-search part of #230.

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The binary-search tests force the practitioner to generify the class but only one type (integer) was actually being used in the tests. This should be changed so that more than one type is actually used, to make it more clear that generics are necessary and to demonstrate how generics is used. As discussed in exercism#230, move linked-list to one of the last difficulty 6 exercises, so that binary-seach is the first exercise that introduces generics. Add a hint to the binary-search exercise to explain generics as this is now the first exercise to require it. Fixes exercism#230.

mortenaa · 2017-10-07T14:47:59Z

Is this up for grabs? If so, I can do it :-)

FridaTveit · 2017-10-07T14:52:08Z

What exactly do you mean by "up for grabs"? I've made this PR to solve the issue of using generics in binary-search. So this isn't an issue you can solve, it's a PR solving an issue. If you want to look through it and review it then you can :) There should still be plenty of good-first-patch issues to do if you want to do more PRs :)

mortenaa · 2017-10-07T14:58:31Z

Ah, sorry, I thought I was looking at an issue :-)

FridaTveit · 2017-10-07T15:02:10Z

I see, no problem :)

stkent · 2017-10-17T17:49:22Z

exercises/binary-search/.meta/hints.md

+
+For example you could construct a list of `Integers`:
+
+`List<Integer> someList = new LinkedList();`


Should use LinkedList<>(); here.

stkent · 2017-10-17T17:49:29Z

exercises/binary-search/.meta/hints.md

+
+Now `someList` can only contain `Integers`. You could also do:
+
+`List<String> someOtherList = new LinkedList()`


Should use LinkedList<>(); here.

stkent · 2017-10-17T17:49:57Z

exercises/binary-search/.meta/hints.md

+
+Now `someOtherList` can only contain `Strings`.
+
+Another constraint is that any type used with generics cannot be a [primitive type](https://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html), such as `int` or `long`.


Might be good to add a reminder that every primitive type has a corresponding reference type!

Premitive Type Reference Equvalent

boolean Boolean

byte Byte

short Short

char Character

int Integer

long Long

float Float

double Double

stkent · 2017-10-17T17:50:49Z

exercises/binary-search/src/test/java/BinarySearchTest.java

@@ -13,23 +13,23 @@

    @Test
    public void findsAValueInAnArrayWithOneElement() {
-        List<Integer> listOfUnitLength = Collections.singletonList(6);
+        List<Character> listOfUnitLength = Collections.singletonList('6');


Same question as for custom-set; is there a pattern for the generic types being used now?

Not really. I've tried to use Integer, Character and String and to make sure I've got a couple of tests using each, but I've not got a strict pattern as I didn't think it mattered too much. I could make it a more strict pattern if you think that would be useful?

Nah, I think it's good as-is!

Will change it to cycle through Character, String, Integer as it's probably best to be consistent :)

As I was changing it I remembered why I didn't do that. Some of them can't use Character because they use higher numbers, e.g. 11... So it's only possible to use Character for some of the earlier tests, at least for this exercise. I could make the rest cycle through String and Integer?

As I was changing it I remembered why I didn't do that. Some of them can't use Character because they use higher numbers, e.g. 11... So it's only possible to use Character for some of the earlier tests, at least for this exercise. I could make the rest cycle through String and Integer?

This sounds like a good compromise to me!

Okay, will do that :) Will do that for the others too, try to cycle through all three but skip Character if not possible :)

Sadly, as it turns out String causes problems as well since it will sort it lexicographically and we're using numbers in all our test cases... So should I instead try to cycle through all three, skip Chracter if not possible and also skip String if not possible? And make sure that Character and String are used at least once?

That sounds ideal, yep!

Great, will do that then :)

stkent

Comments inline!

FridaTveit · 2017-10-18T18:10:19Z

Also removed an unused method that I found in the reference implementation :)

stkent · 2017-10-18T19:15:59Z

❤️

Merge branch 'master' into BinarySearchUseGenerics

d6e6697

stkent self-assigned this Oct 17, 2017

stkent reviewed Oct 17, 2017

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stkent suggested changes Oct 17, 2017

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Tidy up binary search hints and reference implementation

8b9a7a2

stkent approved these changes Oct 18, 2017

View reviewed changes

stkent merged commit b1a0b1d into exercism:master Oct 18, 2017

FridaTveit deleted the BinarySearchUseGenerics branch November 10, 2017 11:49


		For example you could construct a list of `Integers`:

		`List<Integer> someList = new LinkedList();`


		Now `someList` can only contain `Integers`. You could also do:

		`List<String> someOtherList = new LinkedList()`


		Now `someOtherList` can only contain `Strings`.

		Another constraint is that any type used with generics cannot be a [primitive type](https://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html), such as `int` or `long`.

Premitive Type	Reference Equvalent
boolean	Boolean
byte	Byte
short	Short
char	Character
int	Integer
long	Long
float	Float
double	Double

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binary-search: use generics #868

binary-search: use generics #868

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FridaTveit commented Oct 6, 2017

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FridaTveit commented Oct 18, 2017

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