How to script a comparison of a number against a range?
1 is not within 2-5
or
3 is within 2-5
views:
1572answers:
6
+9
A:
In Perl:
if( $x >= lower_limit && $x <= upper_limit ) {
# $x is in the range
}
else {
# $x is not in the range
}
Adnan
2009-02-28 04:38:20
appreciate the quick replies!
2009-02-28 04:46:56
Um ... I think some sigils are missing. Perl probably does the right thing but you might also want to keep in mind that perl uses floating point as default for numbers, so you have the potential for the 0.999999... == 1.0 problem. But I'm an old Fortran programmer, so discount my words accordingly.
jaredor
2009-02-28 05:25:07
Recent perls try hard to keep integers stored as such.
ysth
2009-03-01 04:25:32
thanks for the edits brian. The invisible $ in perl frequently bites me.
Adnan
2009-03-01 05:25:21
Brad Gilbert
2009-03-01 14:59:52
@ysth, I believe that if you had "$x = 5;" perl should keep it as an integer if possible, but if you had "$x = (1 / 2) * 10;" I would hope it would be kept as a float. Unless the problem domain is specifically restricted to integers, the floating point issue merits at least a consideration.
jaredor
2009-03-02 04:13:29
I almost want to mark this as Perl5, instead of Perl, but it works on Perl6 as well.
Brad Gilbert
2009-07-01 16:02:59
+7
A:
In bash:
$ if [[ 1 -gt 2 && 1 -lt 5 ]]; then echo "true"; fi
$ if [[ 3 -gt 2 && 1 -lt 5 ]]; then echo "true"; fi
true
jcrossley3
2009-02-28 04:42:47
+10
A:
It's even better in
It's even better in Perl6.
Chained comparison operators:
if( 2 <= $x <= 5 ){
}
Smart-match operator:
if( $x ~~ 2..5 ){
}
Junctions:
if( $x ~~ any 2..5 ){
}
Given / When operators:
given( $x ){
when 2..5 {
}
when 6..10 {
}
default{
}
}
Brad Gilbert
2009-02-28 05:44:27
So much of Perl 6 looks awesome that I think I can forgive the few things that don't.
Chris Lutz
2009-02-28 05:55:36
Given/When also works in 5.10, it's one of the things that was back-ported to Perl5.
Brad Gilbert
2009-02-28 15:09:58
Truly, when Perl 6 arrives it will change the way your grandchildren write code.
j_random_hacker
2009-02-28 15:32:56
Since the task can be solved without difficulty in existing Perls, it makes me cringe to see that this answer -- which lists a pile of incredibly marginal improvements from a language that doesn't exist yet -- should be at the top. I'm tempted to -1 this just to reduce the cringe factor.
j_random_hacker
2009-03-01 05:18:40
@j_random_hacker: "doesn't exist yet" is out of date FUD. you could say "not yet released", but it sure does exist: http://www.perl.com/download.csp#perl6
ysth
2009-03-01 11:07:26
They only seem to be "marginal improvements" because this is a trivial example. Junctions are amazing...
jettero
2009-03-01 12:24:01
@jettero: To be clear, I'm not saying that the features themselves are marginal, only that using them to solve this particular problem is.
j_random_hacker
2009-03-02 04:03:05
@ysth: Thanks for the pointer. It looks like Perl 6 is further along than I thought. But a look at the Rakudo feature status page: http://www.perlfoundation.org/perl6/index.cgi?rakudo_feature_status tells me things aren't stable enough yet for anything but playing.
j_random_hacker
2009-03-02 04:32:16
I didn't intend for this to get more up-votes than any other question, I just wanted to spread the word about Perl6.
Brad Gilbert
2009-07-01 16:01:30
+4
A:
The smart match operator is available in Perl 5.10, too:
if ( $x ~~ [2..5] ) {
# do something
}
hillu
2009-03-01 00:57:59
or Quantum::Superpositions. but that or L::MU's any are so horrifically expensive that it curdles my prematurely optimizing blood to think of using them for trivial tests.
ysth
2009-03-02 02:20:23
A:
In perl
grep {/^$number$/} (1..25);
will give you a true value if the number is in the range and a false value otherwise.
For example:
[dsm@localhost:~]$ perl -le 'print "has `$ARGV[0]`" if grep {/^$ARGV[0]$/} (1..25)' 4
has `4`
[dsm@localhost:~]$ perl -le 'print "has `$ARGV[0]`" if grep {/^$ARGV[0]$/} (1..25)' 456
[dsm@localhost:~]$
dsm
2009-03-02 09:49:50
+1
A:
In bash:
if [[ $(echo {2..5}) =~ $x ]]; then echo true; fi
Dennis Williamson
2009-04-21 20:27:36