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Talk:Loops/Increment loop index within loop body

From Rosetta Code

increments the index such that the new index is now that prime[edit]

I must start with the index i 42.
I must increment i until it is prime, so 43. I must now increment i such that the new i is now 43?
I interpreted the sentence ' increments the index such that the new index is now that prime ' to mean you wanted me to set i to 43+43 but this is not what the task specification says.--Nigel Galloway (talk) 14:41, 17 March 2019 (UTC)




Yes, I see your point.   How about:
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Task

Write a loop which:

  •   starts the index (variable) at   42
  •   (at iteration time)   increments the index by unity
  •   if the index is prime:
  •   displays the count of primes found (so far) and the prime   (to the terminal)
  •   increments the index such that the new index is now the (old) index plus that prime
  •   terminates the loop when   42   primes are shown

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Would this be satisfactory?     -- Gerard Schildberger (talk) 00:29, 19 March 2019 (UTC)

Works for me.--Nigel Galloway (talk) 13:25, 21 March 2019 (UTC)

I had (originally) had wording in the task's requirements to make it clear(er)   (ha!, not so much)   that the index was to be (possibly also) incremented   (by the computer program)   by the prime just found, but if done/interpreted another way and the index was incremented by the another "extra"   +1,   (by   do   loop structure mechanism)   the new index   (a prime+prime)   is never a prime, and if the index was incremented   (+1)   by the   do   loop structure mechanism,   no harm was done   (that is, at the worst, an extra check for primality was performed for the new index   prime+prime   instead of   prime+prime+1.   So the extra wording, as it turns out, wasn't necessary, but I wanted the incrementation to be clear.   So this almost (did?) became a   "Who's on first?"   sort of a word mess.     -- Gerard Schildberger (talk) 00:29, 19 March 2019 (UTC)

Well, I suppose the advantage of this description is that it indicates why you should not do this!, +1 for those imperative languages that prevent it--Nigel Galloway (talk) 13:25, 21 March 2019 (UTC)
The task's requirements has been updated (to the above).     -- Gerard Schildberger (talk) 07:54, 22 March 2019 (UTC)

To be clear, does this mean that the first Kotlin solution is an example of what isn't wanted? As I understand it, that solution checks if i is prime, and if it is, it replaces i with 2*i and then checks that. It looks like the Lua and Nanoquery solutions have the same issue, but I'm drifting away from languages that I know. --ReeceGoding (talk) 13:51, 23 June 2020 (UTC)