Re: 'switch' operator improvement
Pattern-matching with views [1,2], anyone ?
Cheers,
David
[1] http://martin.jambon.free.fr/micmatch-manual.html#htoc10
[2] http://blogs.msdn.com/dsyme/archive/2006/08/16/ActivePatterns.aspx
On Tue, 2007-10-16 at 20:11 +0200, liorean wrote:
> On 16/10/2007, Peter Hall <[EMAIL PROTECTED]> wrote:
> > already you can do something like this:
> >
> > var str;
> > switch(true){
> > case /a/.test(str):
> > alert('a');
> > break;
> > case /b/.test(str):
> > alert('b');
> > break;
> > }
>
> I can only imagine that solution being preferable to chained
> if..else-statements in one case, and that would be if you actually
> used the fall through mechanism. If you don't fall through, it's just
> bloat without any gain.
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Re: 'switch' operator improvement
On 16/10/2007, Peter Hall <[EMAIL PROTECTED]> wrote:
> already you can do something like this:
>
> var str;
> switch(true){
> case /a/.test(str):
> alert('a');
> break;
> case /b/.test(str):
> alert('b');
> break;
> }
I can only imagine that solution being preferable to chained
if..else-statements in one case, and that would be if you actually
used the fall through mechanism. If you don't fall through, it's just
bloat without any gain.
--
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Re: 'switch' operator improvement
On Oct 16, 2007, at 8:19 AM, Dave Herman wrote:
> But that's not what you proposed, is it? I understood your proposal to
> mean something more like:
>
> function f(g) {
> if (let (tmp = g())// case g():
> (tmp is RegEx ? tmp.match(x) : x == tmp))
> if
> }
>
> Dave
Right, and that is not only backward incompatible, but user-hostile
unless you type everything. It's perl-ish magic.
I say use an if-else and call match if that is what you want. EIBTI,
the Pythonistas say (Explicit Is Better Than Implicit).
/be
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Re: 'switch' operator improvement
Minor nitpick, but that should be "===" not "==".
I really like the idea, but probably it should be done in a way that
could be generalised beyond just the RegExp case. And that doesn't
seem like something that can be done in the es4 time-frame.
But already you can do something like this:
var str;
switch(true){
case /a/.test(str):
alert('a');
break;
case /b/.test(str):
alert('b');
break;
}
Not quite as neat or readable, but the same functionality and not
overly verbose.
I'd be interested to know how often switch statements are used in the
real-world, that could not be trivially replaced with if..else, ie
without breaks on every case. Has that been previously measured?
Peter
On 10/16/07, Dave Herman <[EMAIL PROTECTED]> wrote:
> But that's not what you proposed, is it? I understood your proposal to
> mean something more like:
>
> function f(g) {
> if (let (tmp = g())// case g():
> (tmp is RegEx ? tmp.match(x) : x == tmp))
> if
> }
>
> Dave
>
> [EMAIL PROTECTED] wrote:
> > I think switch ... case construction must be interpreted as:
> > function f(g) {
> > if( x == g() ) // case g():
> > if( // case ...
> > }
> >
> > - Original Message -
> > From: "Dave Herman" <[EMAIL PROTECTED]>
> > To: "Lars T Hansen" <[EMAIL PROTECTED]>
> > Cc: <[EMAIL PROTECTED]>;
> > Sent: Tuesday, October 16, 2007 6:04 PM
> > Subject: Re: 'switch' operator improvement
> >
> >
> >> It's clever, but it's a special case that may not abstract very
> >> smoothly. For example:
> >>
> >> function f(g) {
> >> switch (x) {
> >> case g():
> >> ...
> >> }
> >> }
> >>
> >> The behavior of my function depends on whether g() returns a RegEx or a
> >> non-RegEx. Maybe that's what you want, but it means it's an extra
> >> special case that you have to be aware of whenever abstracting a case
> >> statement.
> >>
> >> Dave
> >>
> >> Lars T Hansen wrote:
> >>> Neat, though it breaks backward compatibility -- each regexp is
> >>> converted to string before the comparison, IIRC. (Compatibility may
> >>> not be a big problem in practice in this case.)
> >>>
> >>> --lars
> >>>
> >>> On 10/16/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
> allow RegEx in case
>
> var str= 'a';
> switch( str ) {
> case /a/:
> alert('a');
> break;
>
> case /b/:
> alert('b');
> break;
> }
>
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Re: Possibility of standardized sprintf() in ES4?
[ snip ] > Sure. From what I can see of the Microsoft documentation a > standardized String.format() function would meet the need for a > standardized way of formatting a string just as well as a method > based on C/Perl/PHP/Ruby sprintf() and Python's native string > formatting, where named parameters are used instead of positional > parameters. Python allows both, and I prefer that style. > Assuming there are no intellectual property concerns with adopting > Microsoft's specification for this method, it would satisfy my use > case for a string formatting method that accepts explicit positional > or named parameters in support of internationalized text. I would > simply be delighted if ES4 saved me and others from having to roll > our own string formatter classes! Eh, just go w/ Python's. It's more flexible, "feels" more like printf if/when you need it to, and can be used in the .NET-ish way. Regards -- Alex Russell [EMAIL PROTECTED] A99F 8785 F491 D5FD 04D7 ACD9 4158 FFDF 2894 6876 [EMAIL PROTECTED] BE03 E88D EABB 2116 CC49 8259 CF78 E242 59C3 9723 pgp3LKURV6n3e.pgp Description: PGP signature ___ Es4-discuss mailing list Es4-discuss@mozilla.org https://mail.mozilla.org/listinfo/es4-discuss
Re: 'switch' operator improvement
But that's not what you proposed, is it? I understood your proposal to
mean something more like:
function f(g) {
if (let (tmp = g())// case g():
(tmp is RegEx ? tmp.match(x) : x == tmp))
if
}
Dave
[EMAIL PROTECTED] wrote:
> I think switch ... case construction must be interpreted as:
> function f(g) {
> if( x == g() ) // case g():
> if( // case ...
> }
>
> - Original Message -
> From: "Dave Herman" <[EMAIL PROTECTED]>
> To: "Lars T Hansen" <[EMAIL PROTECTED]>
> Cc: <[EMAIL PROTECTED]>;
> Sent: Tuesday, October 16, 2007 6:04 PM
> Subject: Re: 'switch' operator improvement
>
>
>> It's clever, but it's a special case that may not abstract very
>> smoothly. For example:
>>
>> function f(g) {
>> switch (x) {
>> case g():
>> ...
>> }
>> }
>>
>> The behavior of my function depends on whether g() returns a RegEx or a
>> non-RegEx. Maybe that's what you want, but it means it's an extra
>> special case that you have to be aware of whenever abstracting a case
>> statement.
>>
>> Dave
>>
>> Lars T Hansen wrote:
>>> Neat, though it breaks backward compatibility -- each regexp is
>>> converted to string before the comparison, IIRC. (Compatibility may
>>> not be a big problem in practice in this case.)
>>>
>>> --lars
>>>
>>> On 10/16/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
allow RegEx in case
var str= 'a';
switch( str ) {
case /a/:
alert('a');
break;
case /b/:
alert('b');
break;
}
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Re: 'switch' operator improvement
I think switch ... case construction must be interpreted as:
function f(g) {
if( x == g() ) // case g():
if( // case ...
}
- Original Message -
From: "Dave Herman" <[EMAIL PROTECTED]>
To: "Lars T Hansen" <[EMAIL PROTECTED]>
Cc: <[EMAIL PROTECTED]>;
Sent: Tuesday, October 16, 2007 6:04 PM
Subject: Re: 'switch' operator improvement
> It's clever, but it's a special case that may not abstract very
> smoothly. For example:
>
> function f(g) {
> switch (x) {
> case g():
> ...
> }
> }
>
> The behavior of my function depends on whether g() returns a RegEx or a
> non-RegEx. Maybe that's what you want, but it means it's an extra
> special case that you have to be aware of whenever abstracting a case
> statement.
>
> Dave
>
> Lars T Hansen wrote:
>> Neat, though it breaks backward compatibility -- each regexp is
>> converted to string before the comparison, IIRC. (Compatibility may
>> not be a big problem in practice in this case.)
>>
>> --lars
>>
>> On 10/16/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
>>>
>>> allow RegEx in case
>>>
>>> var str= 'a';
>>> switch( str ) {
>>> case /a/:
>>> alert('a');
>>> break;
>>>
>>> case /b/:
>>> alert('b');
>>> break;
>>> }
>>>
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Re: 'switch' operator improvement
It's clever, but it's a special case that may not abstract very
smoothly. For example:
function f(g) {
switch (x) {
case g():
...
}
}
The behavior of my function depends on whether g() returns a RegEx or a
non-RegEx. Maybe that's what you want, but it means it's an extra
special case that you have to be aware of whenever abstracting a case
statement.
Dave
Lars T Hansen wrote:
> Neat, though it breaks backward compatibility -- each regexp is
> converted to string before the comparison, IIRC. (Compatibility may
> not be a big problem in practice in this case.)
>
> --lars
>
> On 10/16/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
>>
>> allow RegEx in case
>>
>> var str= 'a';
>> switch( str ) {
>> case /a/:
>> alert('a');
>> break;
>>
>> case /b/:
>> alert('b');
>> break;
>> }
>>
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>>
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Re: SYNTAX BUG
On 16/10/2007, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > In the next line there is ambigious between RegEx and comment > str.match(//); Not really. // is always a line comment starter in ES3: 7.8.5 Regular Expression Literals /- - -/ NOTE Regular expression literals may not be empty; instead of representing an empty regular expression literal, the characters // start a single-line comment. To specify an empty regular expression, use /(?:)/. -- David "liorean" Andersson ___ Es4-discuss mailing list Es4-discuss@mozilla.org https://mail.mozilla.org/listinfo/es4-discuss
RE: Possibility of standardized sprintf() in ES4?
I would be all for .NET's String.Format() style of formatting. Adobe Flex
provides a similar method in StringUtil.substitute() which provides ordered
substitution using the same {0} and {1} style tokens, but doesn't have any
formatting.
Sam
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-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of zwetan
Sent: Monday, October 15, 2007 5:51 PM
To: Dan Scott
Cc: es4-discuss@mozilla.org
Subject: Re: Possibility of standardized sprintf() in ES4?
Hi,
...
>
> Is there any other interest in adding a native sprintf() (probably as
> String.sprintf()) to the ES4 specs?
>
I'm interested in string formating, but surely not sprintf
I don't find it intuitive at all
I prefer something closer to String.format from .NET
but more dynamic and being able to use sort of tokens
like the ones you can use with E4X ({token})
see here for an implementation
http://maashaack.googlecode.com/svn/trunk/ES4a/src/system/Strings.as
( public static function format( format:String, ...args ):String )
cheers,
zwetan
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Re: 'switch' operator improvement
Neat, though it breaks backward compatibility -- each regexp is
converted to string before the comparison, IIRC. (Compatibility may
not be a big problem in practice in this case.)
--lars
On 10/16/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
>
>
> allow RegEx in case
>
> var str= 'a';
> switch( str ) {
> case /a/:
> alert('a');
> break;
>
> case /b/:
> alert('b');
> break;
> }
>
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>
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'switch' operator improvement
allow RegEx in case
var str= 'a';
switch( str ) {
case /a/:
alert('a');
break;
case /b/:
alert('b');
break;
}
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