WHY is var line getting changed by operations on var base_name? Isn’t
‘base_name = line’ supposed to create a copy? ‘=’ in this case seems to
be acting like an alias or something.
BTW, is there a foreach function that automatically strips off the
newlines from line? Returning the record separators is silly.
WHY is var line getting changed by operations on var base_name? Isn’t
‘base_name = line’ supposed to create a copy? ‘=’ in this case seems to
be acting like an alias or something.
Yep. All variables in Ruby are actually references to objects … so
using the = operator actually signifies “this variable now points at the
same object as that variable”. What you want is probably either:
base_name = line.clone
or
base_name = String.new(line)
but it would probably make more sense to just create base_name at the
first operation where you want the two to be different - for example:
BTW, is there a foreach function that automatically strips off the
newlines from line? Returning the record separators is silly.
Hmmm, not that I know of. However, I just want to mention that you
probably want String#chomp rather than String#strip, unless you actually
want to strip whitespace from the beginning of the string as well.
Currently hating Ruby,
Joe
Watch it - you may be in danger of losing your MUDCRAP certification …
WHY is var line getting changed by operations on var base_name? Isn’t
‘base_name = line’ supposed to create a copy? ‘=’ in this case seems to
be acting like an alias or something.
Nope. Now, you have two variables, base_name and line, referencing the
same object. Try:
base_name = line.dup
BTW, is there a foreach function that automatically strips off the
newlines from line? Returning the record separators is silly.
line.chomp!
Currently hating Ruby,
Be a lover not a fighter!
Jamey
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WHY is var line getting changed by operations on var base_name? Isn’t
‘base_name = line’ supposed to create a copy? ‘=’ in this case seems
to be acting like an alias or something.
No, it isn’t. You’re not understanding Ruby variables and assignment.
Variables in Ruby aren’t locations; they’re names. Objects are the only
things that take up (meaningful) space.
Assignment doesn’t copy.
BTW, is there a foreach function that automatically strips off the
newlines from line? Returning the record separators is silly.
No, it isn’t silly. Sometimes, that’s what people want. You should be
using #chomp or #chomp! to strip that (use #strip or #strip! if and only
if you want to remove whitespace from beginning and end of the line).
WHY is var line getting changed by operations on var base_name? Isn’t
‘base_name = line’ supposed to create a copy? ‘=’ in this case seems to
be acting like an alias or something.
As far as my understanding goes most assignments just copy object
references. Try something like base_name = line.clone.
WHY is var line getting changed by operations on var base_name?
Because in most cases, variable names contain references for the sake of
efficiency. To get the behavior you want, try:
base_name = “” + line
But this is by no means the best thing to do in a lot of cases.
Isn’t
‘base_name = line’ supposed to create a copy? ‘=’ in this case seems to
be acting like an alias or something.
That’s because base_name is an alias or something.
BTW, is there a foreach function that automatically strips off the
newlines from line? Returning the record separators is silly.
Really? How do you split the records after not providing the record
separator character in the saved data?
In a tab-separated database, tabs separate fields, and linefeeds
separate
records. Neither tabs nor linefeeds are allowed within the fields. If
you
remove either the tabs or the linefeeds from the database, you destroy
the
integrity of the database.
Currently hating Ruby,
It’s okay. At the moment, you don’t know enough to make an informed
judgment
about Ruby. When you do, you will like it.
WHY is var line getting changed by operations on var base_name?
Because in most cases, variable names contain references for the sake of
efficiency.
And I’m guessing the sake of simplicity too. The Ruby basic data item
object is thus one-dimensional, objects hold data, and variables point
to objects. Contrasting with C, where either variables hold data, or
heap memory holds data, and variables point to heap memory, or (ye gods)
C++, where references add yet another dimension to the variable / data
relationship (and that you can override the behaviour to do something
else when a data item changes the way it’s being referenced
arbitrarily), this is -much- simpler to understand (when learning as a
first system, not if used to a PHPesque ad-hoc mixture of behaviours),
and what’s more important, it’s easier to keep a single set of quirks to
watch out for when using other peoples’ code, or designing reusable code
(e.g. to avoid clobbering a library’s internal state, etc.); although it
-is- a net loss of language expressivity. Indeed, AFAIK, even the
predominant C++ practice is “pick pointers or references and stick with
them throughout your code” for the common case.
