Hi all!
The problem is this:
I don't fully understand how, when or why to use the map function -
The first book I got on perl only mentions map in passing and says its syntax
is the same as grep, but instead of returning $_, it returns the result of
the map expression.
Now, if i try the code below:
my @file = ("line 1", "line 2", "line 3", "line 4", "line 5");
my @test = map {/5/} @file;
The result when I print @test is:
1
As I understand things, this is the m/5/ being "true" when it gets to the
last element of the array ,"line 5" (- though if we had wanted the element of
@file that matched we would have used grep).
So far so good -
A common example is:
my @words = map {split ' ', $_} @file;
which splits the @file array into words using spaces. Again, as I understand
things, we get the words in @words because the split returns all the words
from $_.
Would it be fair to say we would use map when we expect to have the
expression return a list?
How would I go about creating a second array using map or grep without
changing the original? Can I do that at all?
For example:
my @elements = map {s/line/element/} @file;
just gives "11111" - the "true" values from the substitutions I assume, but
changes @file. grep gives me the result in @elements that I want, but it,
too, changes @file.
I know it sounds simple, but I just have the feeling that I'm missing some
vital information, somehow :(
Thanks in advance for the help ;)
Tom Watson
