Make MCSE for constant arrays always return a NaN

[sethaxen]

Fixes #122

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.70%. Comparing base (877214d) to head (b73fae2).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #128      +/-   ##
==========================================
+ Coverage   96.68%   96.70%   +0.01%     
==========================================
  Files          10       10              
  Lines         875      880       +5     
==========================================
+ Hits          846      851       +5     
  Misses         29       29              

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[coveralls]

Pull Request Test Coverage Report for Build 11894022521

Details

• 5 of 5 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 96.705%

---

Totals
Change from base Build 11882481146:	0.02%
Covered Lines:	851
Relevant Lines:	880

---

💛 - Coveralls

[sethaxen]

#129 should be merged first

[devmotion]

Suggested change

	if all(==(first(x)), x)
	if allequal(x)

[sethaxen]

Since allequal was introduced in Julia v1.8, we would need to either drop support for Julia v1.6-1.7 or add Compat to use it.

[devmotion]

I think we should use allequal at least on newer Julia versions since there's no reason to avoid the specialized implementations for ranges or other special types. I assume if we don't use allequal right away, then it's very likely we'll never switch to the better/native approach even when support for older Julia versions is dropped.

I'd be fine with dropping support for 1.6 and 1.7 now that 1.10 is the new LTS (I'd even be fine with dropping support for < 1.10). Alternatively, to avoid adding a Compat dependency, we could also add our own custom, less-optimized function

if VERSION < v"1.8"
    _allequal(x) = isempty(x) || all(isequal(first(x)), x)
else
    const _allequal = allequal
end

[sethaxen]

I'm okay with bumping support to v1.8. I see no problem with supporting v1.8 and v1.9 until it becomes at all cumbersome to do so.