Improve Space a bit

[KeitaNakamura]

No description provided.

[codecov-io]

Codecov Report

Merging #40 (24ff25e) into main (0bbefe3) will decrease coverage by 0.21%.
The diff coverage is 90.00%.

@@            Coverage Diff             @@
##             main      #40      +/-   ##
==========================================
- Coverage   94.22%   94.01%   -0.22%     
==========================================
  Files          12       12              
  Lines         797      802       +5     
==========================================
+ Hits          751      754       +3     
- Misses         46       48       +2     

Impacted Files	Coverage Δ
src/Space.jl	89.39% <81.81%> (-2.41%)	⬇️
src/AbstractTensor.jl	93.75% <100.00%> (ø)
src/Tensor.jl	97.19% <100.00%> (ø)
src/simd.jl	100.00% <100.00%> (ø)

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