v0.4.2

MultivariateMoments v0.4.2

Diff since v0.4.1

Merged pull requests:

• Add manual rank check and doc (#52) (@blegat)
• Minor cleanup (#53) (@blegat)
• Index nullspace with monomials (#54) (@blegat)
• Use rank interface for standard monomials (#55) (@blegat)
• Implement sieve for standard monomials (#56) (@blegat)
• Add MacaulyNullspaceSolver (#57) (@blegat)