How to change string in local scope

New to Julia
1

Hello, guys! I am new to Julia. Help me please. I want to change my string initialized in upper local scope, and then use it there

text = "abacaba"
text_result = "" #string must be changed

for rule in 1:5
    if i % 2 == 1 #some condition
        text_result = replace(text, "a" => "b", count=1) #this is another string
    end
end
print(text_result) # empty string will be printed
2

To re-assign the global variable text_result you need global in the loop.

I highly recommend creating a function around this loop with text_result as an input (in which case you do not need global).

1 Like
3

If the loop is not inside a function you need to declare test_results as a global AFAIK:

text = "abacaba"
text_result = "" #string must be changed

for rule in 1:5
    if i % 2 == 1 #some condition
       global text_result = replace(text, "a" => "b", count=1) #this is another string
    end
end
print(text_result) # not empty string will be printed
1 Like
4

The best advice is to use Jupyter, which does not have this issue. The code will work the way that is intuitive. Otherwise, put any for loops in a function when working in the REPL or a .jl file.

If you follow those rules and ever have to write global, then (as a beginner) you are probably are doing something you shouldnā€™t

5

Nah, this is not ā€œthe best adviceā€. The best advice is exactly what happened here, someone learned about what a global variable is and how to change itā€™s binding and then went on coding exactly as before. There is absolutely no need to completely change your coding environment because of this.

5 Likes
6

The best advice is to make a new user learn about a complicated and frequently hated scoping rule that is only beloved by people who commit to core compiler? Furthermore, one which is completely alien to every other language the user may come from?

Or, alternatively, get started in a the beginner friendly environment and hope people eventually fix this problem - as has been discussed for a year.

I stick with my advice: Use jupyter, and wrap things in functions when you are not in jupyter.

7

Sorry if we seem to be jumping all over you here, but bear in mind, there are some of us who absolutely detest Jupyter, I donā€™t think itā€™s a great idea to give people the impression that there is somehow something wrong with Julia outside of Jupyter. Of course, if someone wanted to use it anyway, itā€™s great to present it as an option.

1 Like
8

Complicated? It took one sentence and the reply was marked as a solution. Anyway, I am not going to pollute this thread further, I just didnā€™t want a bad advice stand uncontested.

2 Likes
10

Why would you use text_result as an input? Strings are immutable, so you cannot change them. The scoping issue seems to me a red herring.

for rule in 1:5  
    if i % 2 == 1 # what is i supposed to be here??
        text_result = replace(text, "a" => "b", count=1) #this is another string
    end
end

This code just takes text and replaces the first ā€˜aā€™ with ā€˜bā€™, over and over. You can replace your code with this function:

textrep(text) = replace(text, "a"=>"b", count=1)

Actually, you should use characters instead of strings in the replace call, since it is faster:

textrep(text) = replace(text, 'a'=>'b', count=1)

In summary: There is no point in pre-allocating text_result because it just gets thrown away each time you assign the output from replace to it.

1 Like
11

Sorry, I meant text.