my $first = (split /=/, $string)[0];
# or even...
my ($first) = split /=/, $string;
_____________________________________________________
Jeff japhy Pinyan:
Perl,
regex,
and perl
hacker.
s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??; | [reply]
[d/l] |
I think the problem is that when you use shift, you're trying to alter its argument, which you can't alter (I haven't tried that particular maneuver, but I imagine it's the same error I get from pop=~s/foo/bar/). The solution is pretty simple, though: treat the split return as a list (I believe this is one of those cases where the difference between a list and an array matters), which you can index things out of, like so:
my $first = (split//,$string)[0];
Note that if you want to use this as the first argument to a list operator (such as print), you need to do something to keep it from interpreting (split //, $string) as the arguments to the list operator (using the "if it looks like a function" rule), and complaining that you can't take an index out of print (can you tell I'm familiar with the error messages? ;-) :
print +(split//,$string)[4];
If God had meant us to fly, he would *never* have given us the railroads.
--Michael Flanders | [reply]
[d/l]
[select] |
I mean, split returns a list; a list can be interpreted as an array; pop expects an array. Seems logical to me?
Yes, but backwards from the way the language works. Sorry, them's the breaks. This code doesn't work:
1++;
So I'll make a terrible analogy which someone like Dominus will have to correct, but maybe it'll help.
A constant is not a scalar. A scalar can hold a constant. (told you it was bad). A list is not an array. An array can hold a list. You can use a scalar anywhere you can use a constant, but you can't use a constant anywhere you can use a scalar. You can use an array anywhere you can use a list, but you can't use a list anywhere you can use an array.
One's read only, and the other's modifiable. That's why you can perform operations on scalars and arrays.
Make sense? | [reply]
[d/l] |
I don't think there's really a good reason from a language point of view why shift doesn't do what you want. It seems like an implementation issue. The interpreter could create a temporary array that can be modified by shift, but it just doesn't, because nobody thought it should. I'm not sure if I think it should or not.
You can get the "car" (couldn't they have thought of a better name?) of an array like this:
@x[1..$#x]
But that's ugly and probably inefficient. And you have to actually assign your list to @x first, so you can't wedge it into the middle of an expression. Too bad you can't give an open-ended array slice, like this:
(split / /, $string)[1..]
Perl arrays are different from lisp lists. Some things that are easy with one may not be easy with the other. How could it be otherwise?
Update: Did I get car and cdr mixed up again? I can't imagine how I could be so careless. Contents of address register, contents of decrement register - the difference couldn't be clearer! | [reply]
[d/l]
[select] |
You can get the "car" (couldn't they have thought of a better name?)...
Did I get car and cdr mixed up again?I can't imagine how I could be so careless.
In Common Lisp, you may freely use 'first' instead of 'car'
and 'rest' instead of 'cdr' - they're completely identical.
I tend to use first/rest when I'm thinking of something as a list, and car/cdr
when I'm thinking of it as a cons cell, but that's hardly a hard and
fast rule, even for me.
| [reply] |