You can (if you *really* have to) mutate a String by directly accessing
it’s data field like so:
julia> s = "ACTGACTG"
julia> s.data[3] = 'A'
You’ll run into problems if the characters aren’t all the same size though:
julia> a = "∀ x ∈ X"
julia> a.data
11-element Array{Uint8,1}:
0xe2
0x88
0x80
0x20
0x78
0x20
0xe2
0x88
0x88
0x20
0x58
Note how the “length” of the string and the data aren’t the same. If you’re
using this for some Bio-related stuff there’s https://github.com/BioJulia
that might have what you need.
— Mike
