NaN (or ArgumentError) from QGram distances for short strings about stringdistances.jl HOT 4 OPEN

julia> filter(d -> isnan(d(2)("", "")), [QGram, Cosine, Jaccard, Overlap, SorensenDice, MorisitaOverlap, NMD])
6-element Vector{DataType}:
 Cosine
 Jaccard
 Overlap
 SorensenDice
 MorisitaOverlap
 NMD

julia> QGram(1)("", "")
0

julia> QGram(2)("a", "b")
0

julia> function safeevaluate(D::Union{Cosine, Overlap, MorisitaOverlap}, s1, s2)
           length(s1) >= D.q && length(s2) >= D.q && return(evaluate(D, s1, s2))
           throw(ArgumentError("An argument is shorter than q ($(D.q)): \"$s1\", \"$s2\""))
       end
safeevaluate (generic function with 1 method)

julia> D = Cosine(2)
Cosine(2)

julia> @assert safeevaluate(D, "aa", "bb") == evaluate(D, "aa", "bb")

julia> safeevaluate(D, "", "bb")
ERROR: ArgumentError: An argument is shorter than q (2): "", "bb"
Stacktrace:
 [1] safeevaluate(D::Cosine, s1::String, s2::String)
   @ Main ./REPL[2]:3
 [2] top-level scope
   @ REPL[5]:1

julia> function safeevaluate(D::Union{Jaccard, SorensenDice, NMD}, s1, s2)
           (length(s1) >= D.q || length(s2) >= D.q) && return(evaluate(D, s1, s2))
           throw(ArgumentError("An argument is shorter than q ($(D.q)): \"$s1\", \"$s2\""))
       end
safeevaluate (generic function with 2 methods)

julia> safeevaluate(Jaccard(2), "", "")
ERROR: ArgumentError: An argument is shorter than q (2): "", ""
Stacktrace:
 [1] safeevaluate(D::Jaccard, s1::String, s2::String)
   @ Main ./REPL[11]:3
 [2] top-level scope
   @ REPL[12]:1