CODEWITHSUNDEEP
while-loopscopejuliatry-catch
hcp
hcp

Reputation: 347

while loop with try/catch error in Julia logic problem

I'm trying to write a while loop that tests whether an input is valid or not and it keeps asking if the user insists on the wrong input. If it is a valid one, the program just goes on. This is where i'm at.

while true
    try
        selected_row = readline()
        selected_row = parse(Int8, selected_row)
        break
    catch e
        if isa(e, LoadError)
            @warn "type a valid number between [1,8]"
        elseif isa(e, ArgumentError)
            @warn "type a valid number between [1,8]"
        end
    end
end

println("you chose (C|R) ($selected_row)")

The problem is that when the input is correct I get an error.

LoadError: UndefVarError: selected_row not defined

Upvotes: 0

Views: 696

Answers (1)

Bogumił Kamiński
Bogumił Kamiński

Reputation: 69949

The while loop creates a new scope. Now the way to fix the issue depends on where you put your code.

If it is inside e.g. a function then use:

local selected_row

before the loop (inside the function body) and things will work.

If your code is in top-level scope write:

global selected_row = parse(Int8, readline())

in your code which will guarantee that a global variable selected_row will be created.

Having said that I would recommend to write your code as follows:

function get_int8()
    while true
        selected_row = tryparse(Int8, readline())
        isnothing(selected_row) || return selected_row
    end
end

selected_row = get_int8()

Upvotes: 2

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