lfl 2.1.2

• added vignette

lfl 2.1.1

• fixed the minimum required version of R to 3.6

lfl 2.1.0

• the result of algebra() is now an S3 class, implemented print.algebra()
• added involutive negation to algebra()$ni
• added nelson(), lowerEst() handlers of NA for algebra()
• added print() method for linguistic contexts
• added negated=FALSE argument to the lingexpr() function
• implemented bi-residuum of the dragonfly algebra
• implemented order operation of the dragonfly and lowerEst algebras
• added sugeno()
• added fuzzy quantifiers
• deprecated some arguments of the compose() function
• removed deprecated functions: lcut3(), lcut5()

lfl 2.0.1

• added support for percentual quantifiers in compose()
• documentation spell-check