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| Author |
How to get the string Cartesian Products of 2 list
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| xueweizhong@gmail.com 2007-11-22, 10:06 pm |
| Give 2 string list such as: a..b and 1..3, i want to get a list which
is (a1, a2, a3, b1, b2, b3). Is there an elegant way in perl to
fullfill this withou using loop BLOCK? Or Is there a elegant one line
expression to get this?
| |
| Ben Morrow 2007-11-22, 10:06 pm |
|
Quoth xueweizhong@gmail.com:
> Give 2 string list such as: a..b and 1..3, i want to get a list which
> is (a1, a2, a3, b1, b2, b3). Is there an elegant way in perl to
> fullfill this withou using loop BLOCK? Or Is there a elegant one line
> expression to get this?
I don't know whether you count this as using a loop (it does, of course,
underneath; but you can't possibly avoid that at some level)
use List::MoreUtils qw/pairwise/;
my @letters = (a..b);
my @numbers = (1..3);
print for pairwise { "$a$b" } @letters, @numbers;
You have to put the lists into arrays so Perl can tell which items
belong to which list.
Ben
| |
| xueweizhong@gmail.com 2007-11-22, 10:06 pm |
| Hi Ben,
> use List::MoreUtils qw/pairwise/;
>
> my @letters = (a..b);
> my @numbers = (1..3);
>
> print for pairwise { "$a$b" } @letters, @numbers;
It's  , but seems too long, also List::MoreUtils is not standard
distribution
Also i find this URL for adding this into the core language:
http://www.nntp.perl.org/group/perl.../09/msg462.html
| |
|
|
| xueweizhong@gmail.com 2007-11-23, 4:22 am |
| Finally i got this one on bash3.0:
print qx'bash -c "echo {1..3}{a..c}"'
Perl is the glue language and there are more than one way to do it:-)
| |
| Lars Haugseth 2007-11-23, 8:05 am |
|
* xueweizhong@gmail.com wrote:
>
> Give 2 string list such as: a..b and 1..3, i want to get a list which
> is (a1, a2, a3, b1, b2, b3). Is there an elegant way in perl to
> fullfill this withou using loop BLOCK? Or Is there a elegant one line
> expression to get this?
$ perl -le '@list = glob "{a,b}{1,2,3}"; print join(",", @list);'
a1,a2,a3,b1,b2,b3
--
Lars Haugseth
"If anyone disagrees with anything I say, I am quite prepared not only to
retract it, but also to deny under oath that I ever said it." -Tom Lehrer
| |
| Michele Dondi 2007-11-23, 8:05 am |
| On Thu, 22 Nov 2007 19:22:57 -0800 (PST), xueweizhong@gmail.com wrote:
>Also i find this URL for adding this into the core language:
>http://www.nntp.perl.org/group/perl.../09/msg462.html
Into the core of *another* language! ;)
Michele
--
{$_=pack'B8'x25,unpack'A8'x32,$a^=sub{po
p^pop}->(map substr
(($a||=join'',map--$|x$_,(unpack'w',unpack'u','G^<R<Y]*YB='
..'KYU;*EVH[.FHF2W+#"\Z*5TI/ER<Z`S(G.DZZ9OX0Z')=~/./g)x2,$_,
256),7,249);s/[^\w,]/ /g;$ \=/^J/?$/:"\r";print,redo}#JAPH,
| |
| Michele Dondi 2007-11-23, 8:05 am |
| On Thu, 22 Nov 2007 21:40:06 -0800 (PST), xueweizhong@gmail.com wrote:
>Finally i got this one on bash3.0:
>
> print qx'bash -c "echo {1..3}{a..c}"'
>
>Perl is the glue language and there are more than one way to do it:-)
Perl does glob() espansion too.
Michele
--
{$_=pack'B8'x25,unpack'A8'x32,$a^=sub{po
p^pop}->(map substr
(($a||=join'',map--$|x$_,(unpack'w',unpack'u','G^<R<Y]*YB='
..'KYU;*EVH[.FHF2W+#"\Z*5TI/ER<Z`S(G.DZZ9OX0Z')=~/./g)x2,$_,
256),7,249);s/[^\w,]/ /g;$ \=/^J/?$/:"\r";print,redo}#JAPH,
| |
| xueweizhong@gmail.com 2007-11-23, 7:05 pm |
| Hi Michele,
perl glob in perl5.8 is not power enough than the bash3.0 glob, it
doesn't support .. operator which is fatal to this issue:
#!/bin/perl
sub X {split / /,qx/bash -c "echo @_"/}
print "glob:\n";
print join "\n", glob "{a..b}{1..2}";
print "\n\nX:\n";
print join "\n", X "{a..b}{1..2}";
glob:
a..b1..2
X:
a1
a2
b1
b2
| |
| Lars Haugseth 2007-11-23, 7:05 pm |
|
* xueweizhong@gmail.com wrote:
>
> Hi Michele,
>
> perl glob in perl5.8 is not power enough than the bash3.0 glob, it
> doesn't support .. operator which is fatal to this issue:
Why? In practice, the lists being globbed are likely to be variables,
not hard coded inside the glob call.
{
local $" = ','; # List separator
my @letters = 'a'..'c';
my @numbers = 1..3;
my @globbed = glob "{@letters}{@numbers}";
print "@globbed\n";
}
Highly preferrable to forking a new shell process.
--
Lars Haugseth
"If anyone disagrees with anything I say, I am quite prepared not only to
retract it, but also to deny under oath that I ever said it." -Tom Lehrer
| |
| xueweizhong@gmail.com 2007-11-23, 7:05 pm |
| > > perl glob in perl5.8 is not power enough than the bash3.0 glob, it
>
> Why? In practice, the lists being globbed are likely to be variables,
> not hard coded inside the glob call.
>
> {
> local $" = ','; # List separator
>
> my @letters = 'a'..'c';
> my @numbers = 1..3;
>
> my @globbed = glob "{@letters}{@numbers}";
>
> print "@globbed\n";
>
> }
I do think these lines are worse than using loop BLOCK. What I want is
an single expression, not statements with so many nosiy lines.
| |
| brian d foy 2007-11-23, 7:05 pm |
| In article
<3bc8b657-828f-4cde-bbf5-9d9c09b8e59f@s8g2000prg.googlegroups.com>,
<xueweizhong@gmail.com> wrote:
> Give 2 string list such as: a..b and 1..3, i want to get a list which
> is (a1, a2, a3, b1, b2, b3). Is there an elegant way in perl to
> fullfill this withou using loop BLOCK? Or Is there a elegant one line
> expression to get this?
Although you've already said that you don't want non-core modules,
Set::CrossProduct can help here. It wouldn't be useful for this trivial
example, but for large sets it comes in handy. It provides an iterator
to get the next item so you don't have to compute the entire list at
once.
Good luck, :)
| |
| xueweizhong@gmail.com 2007-11-23, 7:05 pm |
| Hi brian,
> Although you've already said that you don't want non-core modules,
> Set::CrossProduct can help here. ...
Really . I'll study it.
BTW, bash is more common than non-standard perl module, right? :-)
-Todd
| |
| Michele Dondi 2007-11-23, 7:05 pm |
| On Fri, 23 Nov 2007 08:13:15 -0800 (PST), xueweizhong@gmail.com wrote:
>
>Really . I'll study it.
>
>BTW, bash is more common than non-standard perl module, right? :-)
It depends... what if you want your program to run under Windows as
well? Of course Win32 ports of bash do exist. But would you expect
people to install one for a single line in your script?
Michele
--
{$_=pack'B8'x25,unpack'A8'x32,$a^=sub{po
p^pop}->(map substr
(($a||=join'',map--$|x$_,(unpack'w',unpack'u','G^<R<Y]*YB='
..'KYU;*EVH[.FHF2W+#"\Z*5TI/ER<Z`S(G.DZZ9OX0Z')=~/./g)x2,$_,
256),7,249);s/[^\w,]/ /g;$ \=/^J/?$/:"\r";print,redo}#JAPH,
| |
| Ben Morrow 2007-11-23, 7:05 pm |
|
Quoth xueweizhong@gmail.com:
>
> Really . I'll study it.
>
> BTW, bash is more common than non-standard perl module, right? :-)
Depending on your frame of reference, maybe. However, if you package up
your Perl program properly (see perlnewmod), you can get perl to install
modules for you automatically, which is rather harder to arrange for
bash. :)
Ben
| |
| Lars Haugseth 2007-11-23, 7:05 pm |
|
* xueweizhong@gmail.com wrote:
>
> I do think these lines are worse than using loop BLOCK. What I want is
> an single expression, not statements with so many nosiy lines.
Err, what do you mean? The only "extra" statement here is the setting
of $" to make the glob and print more readable. The rest is assignments
and output, just there to make the example complete. How would you have
done this using loops with less expressions?
--
Lars Haugseth
"If anyone disagrees with anything I say, I am quite prepared not only to
retract it, but also to deny under oath that I ever said it." -Tom Lehrer
| |
| xhoster@gmail.com 2007-11-23, 7:05 pm |
| xueweizhong@gmail.com wrote:
> Hi brian,
>
>
> Really . I'll study it.
>
> BTW, bash is more common than non-standard perl module, right? :-)
Apparently "bash3.0" isn't common enough. All the machines I've looked
at, many fairly new, don't have it. And on those versions, ".."
is just literal.
Xho
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this fact.
| |
| Ted Zlatanov 2007-11-23, 7:05 pm |
| On Fri, 23 Nov 2007 07:59:26 -0800 (PST) xueweizhong@gmail.com wrote:
[color=darkred]
x> I do think these lines are worse than using loop BLOCK. What I want is
x> an single expression, not statements with so many nosiy lines.
What you perceive as noise are actually good Perl programming
practices. If you don't like them, you could do:
# the original is much better code
print glob sprintf("{%s}{%s}", join(',', 'a'..'c'), join(',', 1..3));
# even more bash-like, using in-place interpolation hacks
local $" = ','; # List separator
print glob "{@{['a'..'c']}}{@{[1..3]}}\n";
You should realize that Perl is a programming language and thus does not
have all the shortcuts that bash offers. No Perl solution will satisfy
you if you just want bash. If you want bash, use bash.
Ted
| |
| Dr.Ruud 2007-11-23, 10:07 pm |
| Ted Zlatanov schreef:
> local $" = ','; # List separator
> print glob "{@{['a'..'c']}}{@{[1..3]}}\n";
Command line version:
$perl -wle '
$"=",";
print for glob "{@{[ q{a}..q{c} ]}}{@{[ 1..3 ]}}"
'
a1
a2
a3
b1
b2
b3
c1
c2
c3
--
Affijn, Ruud
"Gewoon is een tijger."
| |
| xueweizhong@gmail.com 2007-11-24, 4:19 am |
| Hi Ruud,
<glob "{@{[ q{a}..q{c} ]}}{@{[ 1..3 ]}}"
Really nice, a pure perl way now rather than dependant on my bash one.
After your inspiration, i get another solution using map:
>perl -e 'print join ",", map { my $g=$_; map $g.$_,1..3 } "a".."c"'
a1,a2,a3,b1,b2,b3,c1,c2,c3
| |
| xueweizhong@gmail.com 2007-11-24, 4:19 am |
| > You should realize that Perl is a programming language and thus does not
> have all the shortcuts that bash offers. No Perl solution will satisfy
> you if you just want bash. If you want bash, use bash.
I use everything I have. Why not do the programming in mutiple
lanugages which complements each other.
--Todd
| |
| Dr.Ruud 2007-11-24, 8:04 am |
| Dr.Ruud schreef:
> Ted Zlatanov schreef:
>
>
> Command line version:
>
> perl -wle '
> $"=",";
> print for glob "{@{[ q{a}..q{c} ]}}{@{[ 1..3 ]}}"
> '
Others:
perl -le'
sub c{local $"=","; "{@_}"}
print for glob c("a".."c").c(1..3)
'
perl -le'
sub c{"{". join(",", @_) ."}"}
print for glob c("a".."c").c(1..3)
'
--
Affijn, Ruud
"Gewoon is een tijger."
| |
| xueweizhong@gmail.com 2007-11-24, 8:04 am |
| > >> local $" = ','; # List separator
Is this difference below a language feature or bug?
[color=darkred]
>perl -e 'local $" = ","; print join ",", <a{@{[q{001}..q{064}]}}>'
a001,a002,a003,a004,a005,a006,a007,a008,
a009,a010,a011,a012,a013,a014,a015,a016,
a017,a018,a019,a020,a021,a022,a023,a024,
a025,a026,a027,a028,a029,a030,a031,a032,
a033,a034,a035,a036,a037,a038,a039,a040,
a041,a042,a043,a044,a045,a046,a047,a048,
a049,a050,a051,
a052,a053,a054,a055,a056,a057,a058,a059,
a060,a061,a062,a063,a064
>perl -e 'local $" = ","; print join ",", <a{@{[q{001}..q{065}]}}>'
a
-Todd
| |
| Michele Dondi 2007-11-24, 8:04 am |
| On Fri, 23 Nov 2007 06:30:10 -0800 (PST), xueweizhong@gmail.com wrote:
>perl glob in perl5.8 is not power enough than the bash3.0 glob, it
>doesn't support .. operator which is fatal to this issue:
I didn't know that bash 3.* did that. In any case, that's good.
In perl, you can currently use a workaround:
>#!/bin/perl
>
>sub X {split / /,qx/bash -c "echo @_"/}
>
>print "glob:\n";
>print join "\n", glob "{a..b}{1..2}";
local ($",$,)=(",", "\n");
print glob "{@{['a'..'b']}}{@{[1..2]}}"
Of course, someone may implement a bash30_glob() to add to File::Glob.
Michele
--
{$_=pack'B8'x25,unpack'A8'x32,$a^=sub{po
p^pop}->(map substr
(($a||=join'',map--$|x$_,(unpack'w',unpack'u','G^<R<Y]*YB='
..'KYU;*EVH[.FHF2W+#"\Z*5TI/ER<Z`S(G.DZZ9OX0Z')=~/./g)x2,$_,
256),7,249);s/[^\w,]/ /g;$ \=/^J/?$/:"\r";print,redo}#JAPH,
| |
| Michele Dondi 2007-11-24, 8:04 am |
| On Fri, 23 Nov 2007 07:59:26 -0800 (PST), xueweizhong@gmail.com wrote:
>I do think these lines are worse than using loop BLOCK. What I want is
>an single expression, not statements with so many nosiy lines.
You can have a single statement, but that's probably even more noisy:
my @globbed = do { local $"=',';
glob "{@{['a'..'c']}}{@{[1..3]}}" };
Michele
--
{$_=pack'B8'x25,unpack'A8'x32,$a^=sub{po
p^pop}->(map substr
(($a||=join'',map--$|x$_,(unpack'w',unpack'u','G^<R<Y]*YB='
..'KYU;*EVH[.FHF2W+#"\Z*5TI/ER<Z`S(G.DZZ9OX0Z')=~/./g)x2,$_,
256),7,249);s/[^\w,]/ /g;$ \=/^J/?$/:"\r";print,redo}#JAPH,
| |
| Michele Dondi 2007-11-24, 8:04 am |
| On Sat, 24 Nov 2007 05:26:24 -0800 (PST), xueweizhong@gmail.com wrote:
>
>Is this difference below a language feature or bug?
>
> a001,a002,a003,a004,a005,a006,a007,a008,
a009,a010,a011,a012,a013,a0
Feature. Try
perl -le 'print for "aa".."bb"'
Michele
--
{$_=pack'B8'x25,unpack'A8'x32,$a^=sub{po
p^pop}->(map substr
(($a||=join'',map--$|x$_,(unpack'w',unpack'u','G^<R<Y]*YB='
..'KYU;*EVH[.FHF2W+#"\Z*5TI/ER<Z`S(G.DZZ9OX0Z')=~/./g)x2,$_,
256),7,249);s/[^\w,]/ /g;$ \=/^J/?$/:"\r";print,redo}#JAPH,
| |
| xueweizhong@gmail.com 2007-11-24, 7:06 pm |
| > >>perl -e 'local $" = ","; print join ",", <a{@{[q{001}..q{064}]}}>'
>
> Feature. Try
>
> perl -le 'print for "aa".."bb"'
>
You misunderstood me. What i want to understand is the difference
between the output of 2 commands below:
1. perl -e 'local $" = ","; print join ",", <a{@{[q{001}..q{064}]}}>'
2. perl -e 'local $" = ","; print join ",", <a{@{[q{001}..q{065}]}}>'
The 2nd one doesn't out of our expection, can you try this to see
what's going on?:
$perl -e 'local $" = ","; print join ",", <a{@{[q{001}..q{065}]}}>'
a
-Todd
| |
| Dr.Ruud 2007-11-24, 7:06 pm |
| xueweizhong@gmail.com schreef:
> Ruud:
>
> Really nice, a pure perl way now rather than dependant on my bash one.
>
> After your inspiration, i get another solution using map:
>
> perl -e 'print join ",", map { my $g=$_; map $g.$_,1..3 } "a".."c"'
> a1,a2,a3,b1,b2,b3,c1,c2,c3
$ perl -wle'
sub mm{my $_0=shift; map {my $g=$_; map $g.$_, @_>1?mm(@_):@{$_[0]}}
@$_0}
print for mm ["a".."c"], [1..3], ["x".."z"], [7..9];
'
a1x7
a1x8
....
c3z8
c3z9
--
Affijn, Ruud
"Gewoon is een tijger."
| |
| Michele Dondi 2007-11-24, 7:06 pm |
| On Sat, 24 Nov 2007 06:08:41 -0800 (PST), xueweizhong@gmail.com wrote:
>You misunderstood me. What i want to understand is the difference
>between the output of 2 commands below:
>1. perl -e 'local $" = ","; print join ",", <a{@{[q{001}..q{064}]}}>'
>2. perl -e 'local $" = ","; print join ",", <a{@{[q{001}..q{065}]}}>'
I'm astonished: unless I'm missing something *very* obvious, the only
difference is that the former prints up to the 064 and the second to
065.
>The 2nd one doesn't out of our expection, can you try this to see
>what's going on?:
>$perl -e 'local $" = ","; print join ",", <a{@{[q{001}..q{065}]}}>'
>a
Aren't you by any chance just experiencing some problem with the
prompt and not printing a newline?
Michele
--
{$_=pack'B8'x25,unpack'A8'x32,$a^=sub{po
p^pop}->(map substr
(($a||=join'',map--$|x$_,(unpack'w',unpack'u','G^<R<Y]*YB='
..'KYU;*EVH[.FHF2W+#"\Z*5TI/ER<Z`S(G.DZZ9OX0Z')=~/./g)x2,$_,
256),7,249);s/[^\w,]/ /g;$ \=/^J/?$/:"\r";print,redo}#JAPH,
| |
| Jim Gibson 2007-11-26, 7:13 pm |
| In article
<9749e8a7-09d0-4382-a10c-52d3df326b2d@s36g2000prg.googlegroups.com>,
<xueweizhong@gmail.com> wrote:
> I use everything I have. Why not do the programming in mutiple
> lanugages which complements each other.
I can think of three reasons: efficiency, consistency, and
maintainability. There are no doubt others.
Efficiency: it is expensive to fork a separate process to perform a
function. While this may not be important for most applications, it can
become a bottleneck for the most critical applications.
Consistency: languages differ in syntax and semantics. I often have
trouble moving from one language to another.
Maintainability: while you may be proficient in multiple languages, the
next guy who has to maintain your code may not be.
So for programs that only you use occasionally, go ahead and mix perl
and bash to your heart's delight. Just don't argue that this is the
best approach for all.
--
Jim Gibson
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