UndefVarError on a defined variable

New to Julia
1

My script in which i have defined a variable (b) as an empty string gives an error saying my variable isn’t defined.

c = "abc"
b = ""
res = []

for i in 1:4
    for i in 1:4
        b * c[rand(1:3)]  # this line gives the error
    end
    push!(res, b)
    b = ""
end

I tried using the global keyword before b in the last line but that made it so res became a list of empty strings.

2

If you do not execute your script within the REPL, then there are strict rules about where variables are accessible.

The documentation about this is here Scope of Variables · The Julia Language

But there are also many posts in this forum where the behavior is explained. See for example Undefined variable in loop - New to Julia - Julia Programming Language (julialang.org) for a more recent one.

In your case:

  • It should work if you add the global keyword, e.g. global b *= c[rand(1:3)]. Note that your code does not update b, but just computes something without updating b.
  • If you use VS Code or Atom/Juno, then you could run you code by selecting and “Shift + Enter”, in which case the rules for REPL apply which are a bit less strict.
2 Likes
3

I changed it a little bit with your help and this worked:

c = "abc"
res = []

for i in 1:4
    b = ""
    for j in 1:4
        b *= c[rand(1:3)]
    end
    push!(res, b)
end

println(res)
1 Like