Re^2: looping in 2d array

While I have no inclination to quarrel with FloydATC's code, his statement in para 1 may be misleading (I, for one, find it easier to type 3 letters rather than seven).

In fact, while some programmers use for and foreach differently, they are indistinguishable except for the spelling ...and either can be used in a C-style loop or a Perlish version with or without an explicit iterator:

C:\>perl -E "my @arr=qw(a b c d); my $a; for $a(@arr) {say $a;}"
a
b
c
d

<c>C:\>perl -E "my @arr=qw(a b c d); my $a; foreach $a(@arr) {say $a;}
+"
a
b
c
d
[download]

And here's brian d foy's response to a question on SO ( http://stackoverflow.com/questions/2279471/whats-the-difference-between-for-and-foreach-in-perl ) back in 2010:

"They used to be separate ideas, but now they are synonyms. Perl figures out what to do based on what's in the ( ) instead of using the keyword. Blame the people who couldn't type an extra four characters. :)

C:\>perl -e "foreach ($i=0;$i<10;$i++) { print $i }" # NB: '-e' & 'pri
+nt'
0123456789
[download]

And though foy's statement doesn't offer a version or date when "used to be separate ideas" changed, nodes here in the Monastery, back at least as far as 2000, disagree -- some globally, and some only with respect to Perl 4 vs. Perl 5.

Just for completeness or merely to be excessively didactic :-), if one changes foy's (5.8?) code to my (5.18) "for" ...

C:>perl -E "for ($i=0;$i<10;$i++) { say $i }" # Irrelevant differences
+ '-E' & 'say'
0
1
2
3
4
5
6
7
8
9
[download]

Come, let us reason together: Spirit of the Monastery -->

Comment on Re^2: looping in 2d array Select or Download Code

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Re^3: looping in 2d array by FloydATC (Deacon) on Nov 02, 2014 at 13:55 UTC
This is true. And beside the point :-) My point was to let Perl worry about the incrementing and bounds checking, eliminating many common problems such as accidently using the wrong counter or off-by-one errors. Personally, I find the keyword `foreach` coupled with a clear, recognizable variable name to be more readable than the `for` keyword which I'm familiar with from several inferior languages. Although I know perfectly well that Perl will do what I mean either way, I keep a clear distinction between the two to avoid confusion. -- FloydATC Time flies when you don't know what you're doing	[reply] [d/l] [select]
Re^4: looping in 2d array by ww (Archbishop) on Nov 02, 2014 at 15:33 UTC
Sorry if my remark gave offense... but my point is that both `for` and `foreach` deal equally well -- and effectively identically -- with Linguist's problem as indicated by the example code in my previous post. Each will cheerfully increment ~~and/or bounds-check~~ (stricken when I engaged brain and realized that I haven't offered an example of bounds-checking in a Perl-style `for` loop nor can I think of one now) with either C-style or Perlish iterators. You believe your mnemonic use of different words is useful to you. I, therefore, believe that para 1 is probably absolutely valid for you. My objection is that para 1 of your earlier post is only a personal opinion (as is this para and the next)... and is phrased in a manner likely to be "misleading" on any question of functionality. "Yes," "ja" and "oui" are equivalents even though they are different words ... but addressing a multi-lingual audience it would surely be unwise to suggest that English speakers would be better served in daily life by using "oui" or that Germans should say "oui" or "yes" as an affirmative. `++$anecdote ne $data`	[reply] [d/l] [select]
Re^4: looping in 2d array by AnomalousMonk (Archbishop) on Nov 02, 2014 at 21:51 UTC
This [distinction between `for` and `foreach`] is ... beside the point ... Given that Linguist identifies him- or herself as "... new to PERL ...", I think ww's point is very apt. As used above, the `for` versus `foreach` distinction is a bit of Perl jargon that needs to be identified as such to the novice Perler. If it is not, it leads to questions like "Ok, so what's the difference between `for` and `foreach`?" This is a question on a par with "When is a door not a door?", except it has no amusing punchline; instead, there is only the tragic realization that you've just thrown away a few-score seconds of your life pondering a stupid question. I had originally not up-voted ww's posts on this point, but have now done so as a show of solidarity forever! against jargon masquerading as idiom.	[reply] [d/l] [select]