v0.4.0

Libtask v0.4.0

Diff since v0.3.4

Closed issues:

• SMC sampling with Julia 1.1 produces samples with 0 variance for discrete RVs! (#39)
• Hang under Julia 1.5 and nightly. (#59)
• Make a CTask struct (#64)

Merged pull requests:

• Compatibility to Julia 1.5 (#60) (@KDr2)
• Rename taskcopy.jl to ctask.jl (#62) (@yebai)
• (Too) many changes... (#65) (@devmotion)
• Try some expressions (#66) (@devmotion)