«

Hi,


When I use split, there are serveral case frequently occured:

case1:

split # default to split ' ', $_

case2:

split /xxx/ # default to split /xxx/, $_

case3:

split ' ', expr # ????


I do think case3 is most frequently used, but why i've to type ' '
every time, why there are no simpler syntax to use in this case?


Thanks,
Todd

>>>>> "Todd" == Todd <> writes:

Todd> case3:

Todd> split ' ', expr # ????


Todd> I do think case3 is most frequently used, but why i've to type ' '
Todd> every time, why there are no simpler syntax to use in this case?

Because split is positional, and it's only 4 characters to type that, and it's
not *that* common.

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Todd <> wrote in news:20d30e4a-8ded-4a3a-a99b-
:

> case2:
>
> split /xxx/ # default to split /xxx/, $_
>
> case3:
>
> split ' ', expr # ????
>
>
> I do think case3 is most frequently used, but why i've to type ' '
> every time, why there are no simpler syntax to use in this case?


How would you decide whether the following is case 1 or case 2?

split 'hello';

The designers of the API made a choice that if only one argument is
specified, then it will be interpreted as the pattern.

Sinan

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On Wed, 12 Dec 2007 08:07:57 -0800, Todd wrote:
> split ' ', expr # ????
>
>
> I do think case3 is most frequently used, but why i've to type ' ' every
> time, why there are no simpler syntax to use in this case?

AFAIK the perl built-in functions that have default arguments always only
allow you to remove the right-most argument(s).

That would make it a case of which of these in general are used the most
(written in full for clarity):

split /some pattern/,$_;

or

split ' ',$some_string;

And I can definitely tell you I use the former much more often than the
latter.

For instance:

while (<STDIN>) {
chomp;
my ($n,$v) = split /=/;
}

I probably use split /=/; already more often than I use split; split ' ',
$string and split/ /,$string; combined.

Joost.

Todd wrote:
> When I use split, there are serveral case frequently occured:
> case1:
> split # default to split ' ', $_
>
> case2:
> split /xxx/ # default to split /xxx/, $_
>
> case3:
> split ' ', expr # ????
>
> I do think case3 is most frequently used, but why i've to type ' '
> every time, why there are no simpler syntax to use in this case?

One argument not being mentioned by others so far is that when a Perl
function allows omitting of an argument and thus substituting a default
argument it will be $_. Thisis the typical and expected Perl behaviour.
Interpreting a single argument as the text string rather than the search
pattern would be unexpected and contradictory to the typical behaviour of
all other Perl functions.

jue

Todd <> wrote:
> Hi,
>
> When I use split, there are serveral case frequently occured:
>
> case1:
>
> split # default to split ' ', $_
>
> case2:
>
> split /xxx/ # default to split /xxx/, $_
>
> case3:
>
> split ' ', expr # ????
>
> I do think case3 is most frequently used,

Not by me. When I use split on something other than $_, I almost
always use a pattern other than ' ', which I guess would be case4.

After a brief grep through some code, it looks like the order from most
used to least used would be case2 > case1 > case4 > case3

> but why i've to type ' '
> every time, why there are no simpler syntax to use in this case?


You could define a subroutine name splitd (d for default, as in ' ' being
the default pattern)

Xho

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Quoth "Jürgen Exner" <>:
>
> One argument not being mentioned by others so far is that when a Perl
> function allows omitting of an argument and thus substituting a default
> argument it will be $_. Thisis the typical and expected Perl behaviour.
> Interpreting a single argument as the text string rather than the search
> pattern would be unexpected and contradictory to the typical behaviour of
> all other Perl functions.

Uh huh... like shift, or readline, or the return value of split in
scalar context? There are many things I like about Perl; consistency is
not one of them.



Ben

Ben Morrow wrote:
> Quoth "Jürgen Exner" <>:
>>
>> One argument not being mentioned by others so far is that when a Perl
>> function allows omitting of an argument and thus substituting a
>> default argument it will be $_. Thisis the typical and expected Perl
>> behaviour. Interpreting a single argument as the text string rather
>> than the search pattern would be unexpected and contradictory to the
>> typical behaviour of all other Perl functions.
>
> Uh huh... like shift,

Is not defined on scalars. When argument is omitted it shifts @_ which is as
close as possible to $_

> or readline,

The only argument is mandatory, you cannot omit it and thus cannot default
to $_.

> or the return value of split in scalar context?

Doesn't apply. We are talking about optional function/operator _arguments_
which when omitted will default to $_. Return values are not arguments.

jue

Quoth "Jürgen Exner" <>:
> Ben Morrow wrote:
>
> > or readline,
>
> The only argument is mandatory, you cannot omit it and thus cannot default
> to $_.

Yes. Sorry, that was a thinko; I meant <> and thought that readline had
the same default behaviour. To that list we can add -t, 1-arg open,
close (indeed, lots of the IO functions, including the mess that is
eof), substr, caller, bless, die/warn, exit, localtime, ...

I'm not saying any of these defaults are not sensible and useful, just
that they're far from consistent.

Ben

On Wed, 12 Dec 2007 23:00:28 +0000, Ben Morrow wrote:

> Quoth "Jürgen Exner" <>:
>> Ben Morrow wrote:
>>
>> > or readline,
>>
>> The only argument is mandatory, you cannot omit it and thus cannot
>> default to $_.
>
> Yes. Sorry, that was a thinko; I meant <> and thought that readline had
> the same default behaviour.

Don't forget while(<>) { ... }

> To that list we can add -t

which for /more-or-less/ obvious reasons defaults to _

> 1-arg open, close (indeed, lots of the IO functions, including the mess
that is
> eof), substr, caller, bless, die/warn, exit, localtime, ...
>
> I'm not saying any of these defaults are not sensible and useful, just
> that they're far from consistent.

You're definitely right there.

Joost.