example.jl in trackler-2.2.1.107

- old
+ new

@@ -6,9 +6,11 @@
     s::AbstractString
 
     ISBN(s) = verify(s) ? new(replace(s, "-", "")) : throw(ArgumentError("invalid ISBN string: $s"))
 end
 
+string(s::ISBN) = s.s
+
 function verify(s::AbstractString)
     s = replace(s, "-", "")
     chars = split(s, "")
 
     length(chars) == 10 || return false