On 2/17/14, 5:33 AM, Manu wrote:
On 17 February 2014 16:18, Andrei Alexandrescu
<[email protected] <mailto:[email protected]>>
wrote:
On 2/16/14, 7:42 AM, Manu wrote:
So D offers great improvements to switch(), but there are a few
small
things I wonder about.
TL;DR of my answer to this: at some point we must get used to the
notion that minute syntax tweaks are always possible that make us
feel we're making progress when instead we're just moving the rubble
around.
OT: Do you realise how harsh your posts often appear to people? I often
find I need to restrain myself when replying to your blunt dismissals of
peoples opinions/suggestions.
You're right. I shouldn't have answered because now the thread is
fueling from the answers it's getting. Well actually I did my best in my
post to sugarcoat my opinion of the post, which I found a whine on minor
issues and a collection of entirely petty proposals. Sorry.
Advanced pattern matching and safe downcasting and such - that may be
valuable to discuss. But the concerns expressed in this thread build a
store on saving on typing 'case' and 'break'.
So, you admit that this is a disaster site, but are reluctant to
consider what good may come of it?
I didn't admit that. (And I'm sure this is not an attempt to put words
in my mouth.) That wasn't even the charge. I'll actually quote this
thread's overture: "So D offers great improvements to switch(), but
there are a few small things I wonder about."
I'm not suggesting to move the rubble around a bit, I'm suggesting a
missed opportunity to build something new and useful from the rubble.
I believe even if we implement all of these suggestions (change range
syntax, "break" no longer required, no need for "default") to
perfection, they would have zero consequence on the success of D. I
really do believe that.
There are like, 5 control statements in the language; if, for, while,
foreach, switch. To trivialise their importance is surprising.
It would be surprising. But nobody is.
switch is basically the same in D as in C, which kinda finds a purpose
here and there, but it's built on a rubbish foundation. I can imagine
switch (or something like it) being _extremely_ useful to address whole
new classes of problems (like match in rust and others) if it were just
a little bit less shit.
A match statement would be interesting, but was not asked for. This
thread wrings hands over punctuation and formatting.
[snip some of the said hand wringing]
I think the current switch statement design is a fine design all
things considered (compatibility, law of least surprise, usability,
readability).
Well, I disagree. It offers some improvement over the catastrophic
design that C gave us almost half a century ago, but it doesn't address
the basic un-structured nature of the statement, and deliberately
retains all the elements that made it rubbish back when (for compatibility).
Compatibility and law of least surprise I'll grant you.
Usability and readability, I don't think so. Certainly not compared to
competition.
I think what's clear though, is in order to not violate the first 2
(which I agree there is merit in maintaining), any improvement to switch
would probably need to come in the form of a new structure, like 'match'
in rust, or something designed from the ground-up to not suck, 'select'
maybe.
I concede that switch can't be fixed. Perhaps it should be deprecated
instead.
I don't think we should deprecate switch. And if the to-be-proposed
match/select's main features are small syntactic fixes to switch, I
don't think they're worth adding.
So I guess on that note, I'll leave it there, but I still think it's
worth consideration.
Improving on "switch" is hardly the kind of thing that keeps me awake at
night. Finalizing the language is. Threads. Garbage. Null pointers.
this(this). Allocators. Dynamic libraries. Better punctuation for
"switch" is not even down the list - it's not on the list. And I don't
think it should. If that is, anything could be put on the list by the
loudest voice asking.
The functionality that switch offers is tremendously useful, and it
would be so much more useful if it were cleaned up; people would
actually use it, and probably in a whole bunch of new applications.
I don't think so. Again, I think a nicer switch syntax would do zero for
the success of D.
[snip]
Finally, you didn't address the suggestion to allow assignment of the
switch condition to a properly scoped variable: switch([x =] expression) ?
Some expression results don't have an easily named concept. Performing
the expression on a prior line and assigning to a temp often results in
some pretty stupid variable names polluting the outer scope. And it's
annoying.
That bugzilla is a minor improvement that has precedent in the "if"
statement, so I'd accept "switch (auto var = expr)" if implemented.
Andrei
