fix rand_state type issue and make zygote easier

[GiggleLiu]

No description provided.

[codecov]

Codecov Report

Merging #20 into master will increase coverage by 3.93%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #20      +/-   ##
==========================================
+ Coverage   77.11%   81.05%   +3.93%     
==========================================
  Files           8        8              
  Lines         437      533      +96     
==========================================
+ Hits          337      432      +95     
- Misses        100      101       +1

Impacted Files	Coverage Δ
src/operations.jl	75% <100%> (ø)	⬆️
src/instruct.jl	94.9% <100%> (+2.44%)	⬆️
src/register.jl	72.83% <100%> (ø)	⬆️

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