What is the simplest code to explain a loop?

I was once struggling to teach this to a student, tried several different ideas and the one that finally clicked for him was something like this (Ruby):

puts "hello"
puts "hello"
puts "hello"
puts "hello"
puts "hello"

Is the same as:

5.times do
 puts "hello"
end

Here, I've printed "hello" 5 times. But what if I wanted to print it 100 times? In the top example, I have to copy and paste that line 95 more times, pretty painful. In the bottom example, I just change 5 to 100, much easier.

I think specifically the language 5.times do made sense to him and allowed him to understand that the line of code could be executed more than once. Probably connected a missing idea in his mental model. I suppose, you could also give a model for how computers work, then it would emerge from the model. Eg explain that code is stored as data in memory and there is an instruction pointer keeping track of which one we're on, and then basically break the instructions down to some made up assembly language. I feel like that would work really well for a subset of students but really poorly for most of them 😝

If I would a teacher, I would forbid mentioning “for” and “collection” in one sentence - processing collections should be done with map, foreach, etc(I guess they are called a higher order functions?) and never with loops, where scope is unclear and intention is unclear. Loop can do map, reduce, filter, or all of them at the same time. “for” or “foreach” constructs that accept a code block with the scope of a calling code are just loops in disguise.

just my two opinionated cents on this matter ))

At absolute beginner level, I wish I knew about enumeration (Python)

# in
my_list = ['apple', 'orange']
for index, item in enumerate(my_list):
    print(index, item)

# out
0 apple
1 orange

Counting is the most fundamental thing most humans understand.

counter = 0
while (counter < 10) {
   counter = counter + 1
   print('count', counter)
}

Another guy came up with this:

speedometer = 0
while (speedometer <= 220):
    print("car speed is", speedometer)
    speedometer += 1

And then we can go into and operator with:

speedometer = 0
hold_in_gas = True
while (speedometer <= 220 and hold_in_gas):
    print("car speed is", speedometer)
    speedometer += 1

Do go off the book example:

class Book
  read() {
    for (const p of this.pages) {
      p.read();
    }
  }
}