Repeating a for loop sequence

General Usage
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1

Hey people,

I basically want to include an if condition into my for loop, which repeats the loop with the previews iteration variable, if the condition hasn’t been satisfied.
In this case there are a few things to consider:
First, the loop hast to fill all entries of A.
Since A should be filled with values greater than 4, I wanted to implement a condition wich repeats the loop if S is smaller than 4.

In this example, A[n] equals 0, if the condition wasn’t satisfied for the n’th loop.

A = zeros(Float64,6)
counter = 1
for n = counter:length(A)
S = rand(1:10)

if S > 4
    A[n] = S
else
    n = counter -1  (obviously this didn't work)
end

end

print(A)

2 
A = zeros(Float64,6)

for n in eachindex(A)
local S
while true
    S = rand(1:10)
    if S > 4; break; end
end
A[n] = S
end

print(A)

Should give you what you want. Note that in this concrete example S = rand(5:10) could replace the while loop.

3

Thanks for your answer!
Could you maybe explain the commands while ‘true’ and ‘local’.
Why did you make use of them?

4

I used local S to declare a local variable named S in the scope of the for loop otherwise the while loop would create its own local variable S that is unknown to the outer for loop.
I used while true because I cannot write while S > 4 before a value was bound to S.
I could have also written

for n in eachindex(A)
S = rand(1:10)
while S > 4
    S = rand(1:10)
end
A[n] = S
end

but I don’t like to write S = rand(1:10) twice.

1 Like
5

Indeed, thank you for help !

6

You can still do it in a much shorter way like this:

A = zeros(6)

for n in eachindex(A)
    while (S = rand(1:10)) < 5 end
    A[n] = S
end

print(A)