CODEWITHSUNDEEP
arraysloopsfor-loopjulia
Daniel
Daniel

Reputation: 13

Understanding a for loop in an example

Please rather close or down this post try to teach and help me to understand

As a newbie I have a very hard time to understand the following for loop code in Julia. I am sure this should be the same concept in other languages.

I would highly appreciate someone please in details explain to me why the following code for the mylist[3] would be 23

mylist = [3, 2, 1]

count=3
for i in mylist
  mylist[i]=count
  count=count+10
end

mylist[3] = 23

If you Know a good textbook/source/course to help me please let me know.

Upvotes: 0

Views: 92

Answers (2)

deepakchethan
deepakchethan

Reputation: 5600

First loop: count=3 so mylist[3]=3 then count=13

Second loop: count=13 so mylist[2]=13 then count=23

Final loop: count=13 so mylist[3]=23 Since third element in mylist is changed to 3 in first loop.

Thus you get 23

Upvotes: 1

Chris Rackauckas
Chris Rackauckas

Reputation: 19132

Just walk through the example. You're looping through the values of mylist, so the first i is 3. Therefore mylist[i]=count makes mylist[3]=3. count=count+10 updates count to be 13. The second time through mylist makes mylist[2]=13 and then count=23. Then, since the first round made mylist[3]=3, we have i=3 in the last round, which sets mylist[i]=count which is now 23. Thus mylist[3]=23.

Use the REPL to walk through it yourself and it'll be more clear. Going step by step like this is a good way to understand code.

Upvotes: 4

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