Re: For Loops and Variables

Jason Cavett wrote:

The discussion was that the use of the variable "i" was not good as it
should be named something that means something (arrayCounter or
whatever) so it is easier to understand the code.

Like the others, I see nothing wrong with using i for a loop index, and good
reasons to prefer that common idiom in many cases (the fact that it /is/ a
common idiom not least amongst them).

It might be worth saying a bit about /why/ it is acceptable, although it
appears to break the general rule about preferring communicative names.

Somewhat less than half the point is that there is no real need for long
identifiers here -- that's to say that a (very) short identifier is just as
communicative as a long one in this context. And -- all things being equal --
short identifiers are to be preferred over long ones. (The qualification, "all
things being equal" is, of course, /vital/) In any sensible code, the array
index's scope is limited to the loop over the array -- which is a very limited
scope, so the amount of information the identifier must convey is similarly
limited. There is nothing for it to say that is not immediately evident from
the context in which it appears, simply because it only /exists/ in that
immediate context.

The bigger part of the point is that there (usually) is nothing much for the
identifier to communicate /anyway/. It is an array index, and once you've said
that, there isn't (usually) anything else to add. The meaning (usually) lies
in the thing found in the array, at the index, not in the index itself.

The repeated "(usually)" in the above are because of occasional exceptions to
the rule. Perhaps the most common (which Gordon has already touched on) is
when you are considering row/column indexes in 2D arrays. In such cases it can
be sensible to keep it clear whether an index varies over rows or columns.
That is especially true if you are also messing with X/Y coordinates in the
same code (such as painting a grid), since the normal English word order for
rows and columns ("row" then "column" ;-) is inconsistent with that for "x" and
"y" -- which can easily turn the code into a nightmare unless you take steps to
make the relationships explicit. There are other examples, but that one is
probably sufficient...

-- chris


.

Relevant Pages

  • Re: Perlish map() function
    ... the reference material, the Array constructor was introduced in JavaScript ... evaluation would result in a ReferenceError. ... identifier shows that it is true. ...
    (comp.lang.javascript)
  • Re: questions about arrays
    ... > If an array is declared static in file A is it still valid to access ... An identifier declared as 'static' at ... declaring an object as 'static' prevents ... different platform), then you'll have to use different method of saving ...
    (comp.lang.c)
  • Re: parse efficiently
    ... first column is always an identifier which I don't require, ... 1223*1 cell array ... % classes of unequal/missing alleles and equal alleles ...
    (comp.soft-sys.matlab)
  • Re: How to protectdat in fortran 90 modules
    ... >> it's not clear wether func is an array or a function. ... it's an identifier followed by an assignment operator, ... no deficiencies and the other way is to make it so complicated ...
    (comp.lang.fortran)
  • Accessing Hash of hash of arrays
    ... a hash of hashes where the value is an array. ... I looked at the perlref as suggested in the error message and found this: ... Anywhere you'd put an identifier as part ... I'm trying that one to access the hash but still come up with the error. ...
    (comp.lang.perl.misc)