UndefVarError on a defined variable

New to Julia
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.
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