add filter, update uniq, fix concatenation

[9il]

No description provided.

[codecov-io]

Codecov Report

Merging #247 into master will increase coverage by 0.01%.
The diff coverage is 95.55%.

@@            Coverage Diff             @@
##           master     #247      +/-   ##
==========================================
+ Coverage   91.35%   91.37%   +0.01%     
==========================================
  Files          52       52              
  Lines       10192    10227      +35     
==========================================
+ Hits         9311     9345      +34     
- Misses        881      882       +1     

Impacted Files	Coverage Δ
source/mir/date.d	94.20% <ø> (ø)
source/mir/ndslice/internal.d	72.00% <ø> (+0.57%)	⬆️
source/mir/algorithm/iteration.d	85.97% <93.54%> (+0.24%)	⬆️
source/mir/ndslice/concatenation.d	98.88% <100.00%> (+0.03%)	⬆️
source/mir/ndslice/slice.d	97.30% <100.00%> (-0.01%)	⬇️
source/mir/rc/array.d	80.24% <100.00%> (ø)
source/mir/exception.d	13.88% <0.00%> (+2.77%)	⬆️

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