add evaluable functor: max

[ichiban]

#144

[codecov-commenter]

Codecov Report

Merging #165 (0f35aac) into main (84e4119) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #165      +/-   ##
==========================================
+ Coverage   95.37%   95.40%   +0.02%     
==========================================
  Files          19       19              
  Lines        5903     5935      +32     
==========================================
+ Hits         5630     5662      +32     
  Misses        228      228              
  Partials       45       45              

Impacted Files	Coverage Δ
engine/number.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 84e4119...0f35aac. Read the comment docs.