Repeat n times when iteration number not needed

[Mark Reed]

I have a loop in my code that just needs to execute a certain number of times.  

I don't make any reference to the loop control variable anywhere in the body of the loop, but since the for clauses have to test it against the limit and increment it, I can't use _.  So instead, I just used _i, as a signal that the variable's value was unused.  Does that seem reasonable, or would it be better Go  to just leave it as bog-standard i and not worry about signalling the don't-care condition?

[Caleb Spare]

Just use i anyway in those cases. That's what the code in e.g. the standard library does. If I saw _i, the nonstandard naming would probably trip me up more than a loop variable that's not used within the body of the loop.

-Caleb

On Thu, Apr 2, 2015 at 6:29 PM, Mark Reed <mark...@gmail.com> wrote:

I have a loop in my code that just needs to execute a certain number of times.  

I don't make any reference to the loop control variable anywhere in the body of the loop, but since the for clauses have to test it against the limit and increment it, I can't use _.  So instead, I just used _i, as a signal that the variable's value was unused.  Does that seem reasonable, or would it be better Go  to just leave it as bog-standard i and not worry about signalling the don't-care condition?

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[Caleb Spare]

Or you can do

for range [10]struct{}{} {

  // blah

}

(Joke; please don't do this.)

[Mark J. Reed]

Well, obviously if I were going to do that I would use the iter package.  Much more legible. ;)

--

Mark J. Reed <mark...@gmail.com>

[Jason Gade]

Holy cow, that works. http://play.golang.org/p/wInRfj9jk_

Mind. Blown.

[anl...@gmail.com]

http://play.golang.org/p/X6mCEsIFzI

[Rob Pike]

for i := 0; i < 10; i++

Short, simple, straightforward, clear, obvious, understandable, not a puzzle, not cute, not confusing, just right, just do it.

-rob

--

[Piers]

On Sunday, 5 April 2015 18:38:12 UTC+1, anl...@gmail.com wrote:

> http://play.golang.org/p/X6mCEsIFzI

 

There's a 'subtle' bug..

Out of interest I ran it through 'go vet' and golint and they don't report any problem. 

Is there a tool or invocation of the existing ones which does report unused function parameters?

I suppose a tool could also report 'suspicious' repeats of the same constant, e.g. 10 here, but that might get annoying :)

[Dan Kortschak]

It's a feature. "Any caller can have a loop counting any number of iterations that he wants so long as it is 10." – Henry Ford

[atd...@gmail.com]

On Monday, April 6, 2015 at 11:06:36 AM UTC+2, kortschak wrote:

It's a feature. "Any caller can have a loop counting any number of iterations that he wants so long as it is 10." – Henry Ford

I could have sworn that quote was from Mahatma Gandhi.

[Russel Winder]

On Sun, 2015-04-05 at 14:01 -0700, Rob Pike wrote:
> for i := 0; i < 10; i++
>
> Short, simple, straightforward, clear, obvious, understandable, not a
> puzzle, not cute, not confusing, just right, just do it.
>

Whilst this is the way it has to be done in Go, I think you are wrong
on all counts. This is why things like:

10.times

for _ in 1..10

and other variants have been chosen in other languages.

Without experiments from the psychology of programming folk, making
statements about "understandable" and "not confusing" is simply
opinion not data.

--
Russel.
=============================================================================
Dr Russel Winder t: +44 20 7585 2200 voip: sip:russel...@ekiga.net
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[andrey mirtchovski]

> 10.times

10 times what?

[Shawn Milochik]

On Mon, Apr 6, 2015 at 10:53 AM, andrey mirtchovski <mirtc...@gmail.com> wrote:

>     10.times

10 times what?

Please don't feed the trolls. 

[Russel Winder]

On Mon, 2015-04-06 at 10:54 -0400, Shawn Milochik wrote:
> On Mon, Apr 6, 2015 at 10:53 AM, andrey mirtchovski <
> mirtc...@gmail.com>
> wrote:
>
> > > 10.times
> >
> > 10 times what?

Rob's code fragment was:

for i := 0, i < 10; i++

without a code body, which was nonetheless implied. I just used the
same sort of fragment showing the control without the following code
block.

> >
> Please don't feed the trolls.

Far from being a troll.

[bep]

Troll is a trademark of Norway. I'm from Norway, I can use it ...

I like

    for i := 0, i < 10; i++

It was the first loop construct I learnt. And it still makes sense.

bep

mandag 6. april 2015 17.21.50 UTC+2 skrev Russel Winder følgende:

On Mon, 2015-04-06 at 10:54 -0400, Shawn Milochik wrote:
> On Mon, Apr 6, 2015 at 10:53 AM, andrey mirtchovski <
> mirtc...@gmail.com>
> wrote:
>
> > >     10.times
> >
> > 10 times what?

Rob's code fragment was:

        for i := 0, i < 10; i++

without a code body, which was nonetheless implied. I just used the
same sort of fragment showing the control without the following code
block.

> >
> Please don't feed the trolls.

Far from being a troll.

--
Russel.
=============================================================================

Dr Russel Winder      t: +44 20 7585 2200   voip: sip:russ...@ekiga.net

[Andy Balholm]

My favorite construct for “do this a certain number of times but don’t use the counter for anything else" is REPEAT in Logo:

REPEAT 4 [ FORWARD 100 RIGHT 90 ]

But I can’t even remember how to do a loop in Logo where you do use the counter…

[Mark J. Reed]

Logo makes the iteration count available in the loop body as # whether you want it or not, whether it's a REPEAT loop or a FOREACH loop (in which the current item is also available as ?).  If it is an actual REPEAT loop, then REPCOUNT also returns the same value as the innermost # (in any other context, REPCOUNT returns -1).

But we're talking about Go without the Lo-. For what it's worth, I had no intention of reopening the debate on how to do counting loops; I was just asking if s "don't-care" indicator on the lcv was reasonable, and the answer seems to be "no", so I'll stick to the basic `for i` form.

If I were inclined to add anything to the language for more explicit support of a pure-counting loop, it would probably be to make "range" work on integers, generating a loop from 0 to N-1 for value N.  But that would only handle one common case and I agree that the ensuing worm-can-opening would not be worth it.

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[fatdo...@gmail.com]

i thought the same, but then I thought the answer was so simple that I must be misunderstanding the question.

[Haddock]

Am Montag, 6. April 2015 16:44:41 UTC+2 schrieb Russel Winder:

On Sun, 2015-04-05 at 14:01 -0700, Rob Pike wrote:
> for i := 0; i < 10; i++
>
> Short, simple, straightforward, clear, obvious, understandable, not a
> puzzle, not cute, not confusing, just right, just do it.
>

Whilst this is the way it has to be done in Go, I think you are wrong
on all counts. This is why things like:

    10.times

    for _ in 1..10

and other variants have been chosen in other languages.

+1