Add Duplicate & DuplicateBy

[CorentinClabaut]

closes #121

[mixedCase]

Would definitely be great to have in lo. Perhaps it would be nicer if they were named Duplicates and DuplicatesBy since Duplicate (IMO) gives off the impression of either a function like lo.Fill or lo.Repeat rather than one that returns duplicates.

[CorentinClabaut]

That's a good point.
I'm happy to make the change but before I'll wait on @samber input to be sure he is interested in the function being added.

[samber]

Hi there,

Duplicates looks better than Duplicate 👍

But since this function is not exactly the opposite of Uniq, I would name it FindDuplicates or OnlyDuplicates. WDYT ?

Also:

• is it a "search helper" (find.go) or a "slice helper" ?
• what about the opposite: FindUniq/OnlyUniq ?

Feel free to suggest other names.

[samber]

You can do it in a single loop:

for _, item := range collection {
    duplicated, ok := isDupl[item]
    if !ok {
	isDupl[item] = false
    } else if !duplicated {
	isDupl[item] = true
        result = append(result, item)
    }
}

[CorentinClabaut]

I thought about it but this will actually change the output's order.
For example, with the test input: 1, 2, 2, 1, 2, 3
The output with the 2 loops version would be: 1, 2
Whereas the output with the single loop would be: 2, 1

I Also thought that this way the code was more consistent with DuplicateBy.

WDYT?

[samber]

hell yeah !

i didn't realize order was not conserved

[CorentinClabaut]

Good points!

I'll rename Duplicate/DuplicateBy to FindDuplicates/FindDuplicatesBy and I'll create FindUniques/FindUniquesBy.
I'll also move these functions to find.go

[codecov-commenter]

Codecov Report

Merging #122 (d21f7b5) into master (1a0b4e6) will increase coverage by 0.53%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #122      +/-   ##
==========================================
+ Coverage   89.81%   90.34%   +0.53%     
==========================================
  Files          13       13              
  Lines        1414     1492      +78     
==========================================
+ Hits         1270     1348      +78     
  Misses        141      141              
  Partials        3        3              

Flag	Coverage Δ
unittests	90.34% <100.00%> (+0.53%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
find.go	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 1a0b4e6...d21f7b5. Read the comment docs.