but not this...
https://play.golang.org/p/cZnSNvi7dNU
On Wed, May 2, 2018 at 3:33 PM roger peppe <rogpe...@gmail.com> wrote:
> On 2 May 2018 at 22:06, Michael Jones <michael.jo...@gmail.com> wrote:
> > Ok, weird proposal: Make the per-iteration update part of a for loop
> change
> > from "assignment to assignment or boolean expression" to allow:
> >
> > while COND do {...}:
> >
> > for i:=0; x[i]<4; {...}
> >
> >
> > do {...} while COND:
> >
> > for i:= 0; ; x[i]<4 { ...}
>
> The per-iteration part already allows arbitrary expressions (they
> might even be bool-valued)
> https://play.golang.org/p/Nt9woI7EWRP
>
> >
> > On Wed, May 2, 2018 at 12:33 PM Louki Sumirniy
> > <louki.sumirniy.stal...@gmail.com> wrote:
> >>
> >> It adds absolutely nothing, that's why it should not be accepted. It
> will
> >> lead to a divergence in the way it's used as well. However I think
> maybe run
> >> block once before first condition check would be a useful and powerful
> >> addition. Maybe it shows my age that I even know what do-while
> >> post-conditional loops are, and why they are useful. I have had to write
> >> these more wordy constructs for exactly this purpose several times in a
> >> project I am working on.
> >>
> >> If there could be some less verbose way to flag that the condition only
> be
> >> checked first run. As I am thinking about it I am thinking of some other
> >> ways too, such as adding an or clause in the conditional that only
> checks if
> >> it's the first run, since golang's and and or operators are just
> >> drop-throughs, well, more or less, I mean, the or operator just does
> both
> >> tests and runs the block directly if the first condition passes. Here's
> a
> >> rough sketch of it while I am thinking about it
> >>
> >> for w:= true; w || <cond>; w=false {
> >> ...
> >> }
> >>
> >> This will always run the first time and I can't be certain but I think
> >> that the compiler may skip the assignment second time since it is an
> >> assignment. Still wordy but it is a do-while loop, nevertheless. If the
> >> assignment is repeated each time it's still an overhead cost, however.
> Some
> >> kind of 'do this only once' hint to the compiler maybe. But you see
> what I
> >> mean. This is definitely a case of something Go could use as an
> improvement
> >> and if it was constructed correctly it would not break old code, but
> instead
> >> actually give people a way to improve it when refactoring later on.
> >>
> >> On Wednesday, 2 May 2018 20:43:11 UTC+3, Ian Lance Taylor wrote:
> >>>
> >>> On Wed, May 2, 2018 at 2:48 AM, Hugh Fisher <hugo....@gmail.com>
> wrote:
> >>> >
> >>> > On Tuesday, May 1, 2018 at 10:45:30 PM UTC+10, Ian Lance Taylor
> wrote:
> >>> >>
> >>> >>
> >>> >> A `while` statement would presumably be exactly identical to a `for`
> >>> >> statement with a single condition. So adding a `while` statement
> >>> >> would not add any power to the language, and would add an additional
> >>> >> keyword. All language choices are a cost benefit decision. In this
> >>> >> case the benefit is a looping construct that some people will find
> >>> >> clearer to read and write, and the cost is a new keyword that
> >>> >> everybody needs to learn, and that at this point in the language's
> >>> >> evolution will likely break some, even if not much, existing code.
> I
> >>> >> don't think the benefit is worth the cost.
> >>> >>
> >>> > As for not adding any power, that's why I mentioned if-then-else and
> >>> > switch.
> >>> > Switch with boolean cases is the same as if then else. It's not an
> >>> > obscure
> >>> > side effect either, the Go Tour cheerfully explains how to use it
> >>> > instead of
> >>> > if-then-else if you prefer.
> >>>
> >>> That is not the same thing, though. Yes, if-then-else and switch do
> >>> similar things, but they have a different syntax and are idiomatically
> >>> used in different ways. You can consider if-then-else as syntactic
> >>> sugar for switch, if you like. It's OK for a language to have some
> >>> syntactic sugar.
> >>>
> >>> But in this case you seem to be suggesting that we add `while <cond> {
> >>> <body> }` as an exact duplicate of the existing language construct
> >>> `for <cond> { <body> }`. That's not syntactic sugar. You are
> >>> suggesting that `while` just be a synonym for `for`. We don't need
> >>> two different keywords that mean exactly the same thing.
> >>>
> >>>
> >>> > Hmm, think I will have a look at the formal change proposal
> process...
> >>>
> >>> I encourage proposals but I can tell you upfront that this proposal
> >>> will not be accepted.
> >>>
> >>> Ian
> >>
> >> --
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> >
> >
> >
> > --
> > Michael T. Jones
> > michael.jo...@gmail.com
> >
> > --
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Michael T. Jones
michael.jo...@gmail.com
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