| ||
Mon 2024-04-15
Butterick’s Practical Typography Sat 2024-04-13
Fri 2024-04-12
Wed 2024-04-10
Boy Meets Boy Meets Boys’ Love Tue 2024-04-09
Mon 2024-04-08
Sat 2024-04-06
Thu 2024-04-04
Search
Archives
2023
12 11 10 09 08 07 06 05 04 03 02 01
2022
2021
2020
2019
2018
2017
2016
2015
2014
2013
2012
2011
2010
2009
2008
2007
2006
2005
2004
2003
One good site
MDN
Nelson Minar
Blog licensed under a Creative Commons License
|
Finding the length of an array must be an unusual thing for Perl
programs to do,
because Perl doesn't have an operator for it. It does
have the evil $#:
You may find the length of
array @days by evaluating $#days, as in csh. However, this
isn't the
length of the array; it's the subscript of the last element,
which is a
different value since there is ordinarily a 0th element.
Huh? What does this mean? And is Perl really modelled after csh?
Let's try to do something simple, see how
many arguments were passed to our program:
#!/usr/bin/perl -w
Now let's run it...
print "\$\#ARGV is $#ARGV\n";
/tmp/argv.pl
Huh? -1? This must have been confusing to others too, because it's
documented again in the docs for @ARGV
$#ARGV is -1 /tmp/argv.pl two arguments $#ARGV is 1
$#ARGV is generally the number of arguments
minus one, because $ARGV[0] is the first argument, not
the program's command name itself.
I realize the simple rule is 'the length of @array
is $#array+1', but how dumb is that?
Update:
a friend pointed out you can get length by evaluating
@array in scalar context. Contexts are one of those horrible
features in Perl that make me have to relearn the language every time
I write a program. There's more than one way to do it but
none of them are simple.
|
|
