Re: Command Languages Versus Programming Languages

Liste des GroupesRevenir à l misc 
Sujet : Re: Command Languages Versus Programming Languages
De : rweikusat (at) *nospam* talktalk.net (Rainer Weikusat)
Groupes : comp.unix.shell comp.unix.programmer comp.lang.misc
Date : 11. Oct 2024, 16:15:14
Autres entêtes
Message-ID : <87frp23c3h.fsf@doppelsaurus.mobileactivedefense.com>
References : 1 2 3 4 5 6 7 8 9 10 11
User-Agent : Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux)
Bart <bc@freeuk.com> writes:
On 10/10/2024 17:55, Rainer Weikusat wrote:
Muttley@DastartdlyHQ.org ignorantly rambled:
On Thu, 10 Oct 2024 16:09:49 +0100
Rainer Weikusat <rweikusat@talktalk.net> boring babbled:
Muttley@DastartdlyHQ.org writes:
Its syntax is also a horrific mess.
>
Which means precisely what?
>
Far too much pointless punctuation. An interpreter shouldn't need the vartype
signified by $ or @ once its defined, it should already know.
For the purpose of variable declaration, how's the interpeter going
to
know the type of a variable without being told about it? Obviously, not
at all.
Perl has three builtin types, scalars, arrays and hashes and
each is denoted by a single-letter prefix which effectively creates
three different variable namespaces, one for each type. That's often
convenient, because the same name can be reused for a variable of a
different type, eg:
my ($data, @data, %data);
>
Why would you want to do this?

Because it's convenient. It's possible to have a single variable
denotning something, say $car, and also a variable use to hold a list of
cars which could be named @car.

$data = rand(128);
@data = ($data, $data + 1);
%data = map { $_, 15 } @data;
it's also convenient to type and easy to read due to being concise.
>
Adding shifted punctuation at the start of every instance of a
variable? I don't call that convenient!

It's convenient for declarations, because it's the shortest possible
syntax which can be used to declare the type of a variable.

So, $ is scalar, @ is an array, and % is a hash?

Yes.

Outside of declarations, $ and @ really denote access modes/ contexts,
with $ standing for "a thing" and @ for "a number of things", eg
$a[0]
>
is the first element of the array @a and
>
Now I'm already lost. 'a' is an array, but it's being used with $?
What would just this:
>
 a[0]
>
mean by itself?

Nothing, ie, it's a syntax error.

@a[-3 .. -1]
is a list composed of the three last elements of @a.
>
Sorry, these prefixes look utterly pointless to me. This stuff works
perfectly well in other languages without them.
>
I can write a[i..j] in mine and I know that it yields a slice.

But presumably only if a is actually an array. In Perl, it's a so-called
bareword which was historically just a string. In current Perl, it's
either a filehandle (which can't be indexed) or calling a function named
a (which also can't be indexed).

[...]

What would $a[-3 .. -1] mean?

$a[0]

In list context (denoted by @) the .. operator returns a sequence of
numbers starting from the value on the left and ending with the value on
the right. But because of the $, it's in scalar context. Then, it
returns a boolean value which is false until the left operand becomes
true, then remains true until the right operand becomes true and then
again becomes false. That's supposed to be used for matching ranges of
something. If an operand is a constant expression, it's supposed to
refer to a line number of the last file which was accessed. Eg,

perl -ne 'print if 10 .. 15'  </var/log/syslog

prints lines 10 - 15 from standard input (connected to /var/log/syslog).

For the given example, the value is always false (arithmetically equal
to 0) because -3 cannot occur as line number of a file.

What happens if you have an array of mixed scalars, arrays and hashes;
what prefix to use in front of a[i]?

Elements of arrays or hashes are always scalars.

Date Sujet#  Auteur
29 Mar 24 * Command Languages Versus Programming Languages750Lawrence D'Oliveiro
29 Mar 24 +- Re: Command Languages Versus Programming Languages1candycanearter07
29 Mar 24 +* Re: Command Languages Versus Programming Languages170Muttley
29 Mar 24 i+- Re: Command Languages Versus Programming Languages1Josef Möllers
29 Mar 24 i+* Re: Command Languages Versus Programming Languages9Richard Kettlewell
29 Mar 24 ii`* Re: Command Languages Versus Programming Languages8Muttley
29 Mar 24 ii `* Re: Command Languages Versus Programming Languages7Kaz Kylheku
29 Mar 24 ii  `* Re: Command Languages Versus Programming Languages6Muttley
29 Mar 24 ii   `* Re: Command Languages Versus Programming Languages5Kaz Kylheku
30 Mar 24 ii    `* Re: Command Languages Versus Programming Languages4Muttley
30 Mar 24 ii     +- Re: Command Languages Versus Programming Languages1Janis Papanagnou
30 Mar 24 ii     `* Re: Command Languages Versus Programming Languages2Kaz Kylheku
1 Apr 24 ii      `- Re: Command Languages Versus Programming Languages1Muttley
29 Mar 24 i`* Re: Command Languages Versus Programming Languages159John Ames
29 Mar 24 i +* Re: Command Languages Versus Programming Languages157Muttley
29 Mar 24 i i+- Re: Command Languages Versus Programming Languages1John Ames
29 Mar 24 i i+* Re: Command Languages Versus Programming Languages151Kaz Kylheku
29 Mar 24 i ii`* Re: Command Languages Versus Programming Languages150Muttley
29 Mar 24 i ii +* Re: Command Languages Versus Programming Languages148Kaz Kylheku
29 Mar 24 i ii i+* Re: Command Languages Versus Programming Languages4David W. Hodgins
29 Mar 24 i ii ii+* Re: Command Languages Versus Programming Languages2Johanne Fairchild
30 Mar 24 i ii iii`- Re: Command Languages Versus Programming Languages1David W. Hodgins
30 Mar 24 i ii ii`- Re: Command Languages Versus Programming Languages1Janis Papanagnou
30 Mar 24 i ii i`* Re: Command Languages Versus Programming Languages143Muttley
30 Mar 24 i ii i `* Re: Command Languages Versus Programming Languages142Kaz Kylheku
1 Apr 24 i ii i  `* Re: Command Languages Versus Programming Languages141Muttley
1 Apr 24 i ii i   +* Re: Command Languages Versus Programming Languages139Johanne Fairchild
1 Apr 24 i ii i   i`* Re: Command Languages Versus Programming Languages138Muttley
1 Apr 24 i ii i   i +- Re: Command Languages Versus Programming Languages1Kaz Kylheku
2 Apr 24 i ii i   i `* Re: Command Languages Versus Programming Languages136Johanne Fairchild
2 Apr 24 i ii i   i  +* Re: Command Languages Versus Programming Languages115ram@zedat.fu-berlin.de (Stefan Ram)
2 Apr 24 i ii i   i  i+* Re: Command Languages Versus Programming Languages112Stefan Ram
2 Apr 24 i ii i   i  ii+* Re: Command Languages Versus Programming Languages110Stefan Ram
3 Apr 24 i ii i   i  iii`* Re: Command Languages Versus Programming Languages109Lawrence D'Oliveiro
3 Apr 24 i ii i   i  iii `* Re: Command Languages Versus Programming Languages108David Brown
3 Apr 24 i ii i   i  iii  +- Re: Command Languages Versus Programming Languages1Lawrence D'Oliveiro
3 Apr 24 i ii i   i  iii  +- Re: Command Languages Versus Programming Languages1John Ames
3 Apr 24 i ii i   i  iii  `* Re: Command Languages Versus Programming Languages105Keith Thompson
3 Apr 24 i ii i   i  iii   +* Re: Command Languages Versus Programming Languages100Richard Kettlewell
4 Apr 24 i ii i   i  iii   i+- Re: Command Languages Versus Programming Languages1Muttley
4 Apr 24 i ii i   i  iii   i`* Re: Command Languages Versus Programming Languages98Stefan Ram
5 Apr 24 i ii i   i  iii   i `* Re: Command Languages Versus Programming Languages97Lawrence D'Oliveiro
5 Apr 24 i ii i   i  iii   i  +* Re: Command Languages Versus Programming Languages49Muttley
5 Apr 24 i ii i   i  iii   i  i+* Re: Command Languages Versus Programming Languages3candycanearter07
5 Apr 24 i ii i   i  iii   i  ii`* Re: Command Languages Versus Programming Languages2Muttley
6 Apr 24 i ii i   i  iii   i  ii `- Re: Command Languages Versus Programming Languages1candycanearter07
6 Apr 24 i ii i   i  iii   i  i`* Re: Command Languages Versus Programming Languages45Lawrence D'Oliveiro
6 Apr 24 i ii i   i  iii   i  i `* Re: Command Languages Versus Programming Languages44Alan Bawden
6 Apr 24 i ii i   i  iii   i  i  +* Re: Command Languages Versus Programming Languages13Lawrence D'Oliveiro
8 Apr 24 i ii i   i  iii   i  i  i`* Re: Command Languages Versus Programming Languages12John Ames
9 Apr 24 i ii i   i  iii   i  i  i `* Re: Command Languages Versus Programming Languages11Lawrence D'Oliveiro
9 Apr 24 i ii i   i  iii   i  i  i  +* Re: Command Languages Versus Programming Languages9John Ames
9 Apr 24 i ii i   i  iii   i  i  i  i`* Re: Command Languages Versus Programming Languages8Richard Kettlewell
9 Apr 24 i ii i   i  iii   i  i  i  i +* Re: Command Languages Versus Programming Languages2Janis Papanagnou
9 Apr 24 i ii i   i  iii   i  i  i  i i`- Re: Command Languages Versus Programming Languages1Richard Kettlewell
9 Apr 24 i ii i   i  iii   i  i  i  i `* Re: Command Languages Versus Programming Languages5David Brown
9 Apr 24 i ii i   i  iii   i  i  i  i  `* Re: Command Languages Versus Programming Languages4Lawrence D'Oliveiro
9 Apr 24 i ii i   i  iii   i  i  i  i   `* Re: Command Languages Versus Programming Languages3David Brown
10 Apr 24 i ii i   i  iii   i  i  i  i    `* Re: Command Languages Versus Programming Languages2Lawrence D'Oliveiro
10 Apr 24 i ii i   i  iii   i  i  i  i     `- Re: Command Languages Versus Programming Languages1Kaz Kylheku
9 Apr 24 i ii i   i  iii   i  i  i  `- Re: Command Languages Versus Programming Languages1Kaz Kylheku
6 Apr 24 i ii i   i  iii   i  i  +* Re: Command Languages Versus Programming Languages3Kaz Kylheku
6 Apr 24 i ii i   i  iii   i  i  i`* Re: Command Languages Versus Programming Languages2David Brown
6 Apr 24 i ii i   i  iii   i  i  i `- Re: Command Languages Versus Programming Languages1Muttley
6 Apr 24 i ii i   i  iii   i  i  +- Re: Command Languages Versus Programming Languages1candycanearter07
6 Apr 24 i ii i   i  iii   i  i  `* Re: Command Languages Versus Programming Languages26Muttley
7 Apr 24 i ii i   i  iii   i  i   +* Re: Command Languages Versus Programming Languages22Alan Bawden
8 Apr 24 i ii i   i  iii   i  i   i`* Re: Command Languages Versus Programming Languages21Muttley
8 Apr 24 i ii i   i  iii   i  i   i `* Re: Command Languages Versus Programming Languages20David Brown
8 Apr 24 i ii i   i  iii   i  i   i  `* Re: Command Languages Versus Programming Languages19Muttley
8 Apr 24 i ii i   i  iii   i  i   i   +* Words to the wise (Was: Command Languages Versus Programming Languages)2Kenny McCormack
8 Apr 24 i ii i   i  iii   i  i   i   i`- Re: Words to the wise (Was: Command Languages Versus Programming Languages)1Muttley
8 Apr 24 i ii i   i  iii   i  i   i   `* Re: Command Languages Versus Programming Languages16Kaz Kylheku
8 Apr 24 i ii i   i  iii   i  i   i    +* Phrases that should be banned on Usenet (Was: Command Languages Versus Programming Languages)9Kenny McCormack
9 Apr 24 i ii i   i  iii   i  i   i    i`* Re: Phrases that should be banned on Usenet (Was: Command Languages Versus Programming Languages)8Janis Papanagnou
9 Apr 24 i ii i   i  iii   i  i   i    i +- Re: Phrases that should be banned on Usenet (Was: Command Languages Versus Programming Languages)1D
9 Apr 24 i ii i   i  iii   i  i   i    i `* Re: Phrases that should be banned on Usenet (Was: Command Languages Versus Programming Languages)6candycanearter07
9 Apr 24 i ii i   i  iii   i  i   i    i  `* Re: Phrases that should be banned on Usenet (Was: Command Languages Versus Programming Languages)5Janis Papanagnou
9 Apr 24 i ii i   i  iii   i  i   i    i   +- Re: Phrases that should be banned on Usenet (Was: Command Languages Versus Programming Languages)1candycanearter07
10 Apr 24 i ii i   i  iii   i  i   i    i   `* Re: Phrases that should be banned on Usenet (Was: Command Languages Versus Programming Languages)3Lawrence D'Oliveiro
10 Apr 24 i ii i   i  iii   i  i   i    i    +- Re: Phrases that should be banned on Usenet (Was: Command Languages Versus Programming Languages)1Chris Elvidge
10 Apr 24 i ii i   i  iii   i  i   i    i    `- Re: Phrases that should be banned on Usenet (Was: Command Languages Versus Programming Languages)1candycanearter07
9 Apr 24 i ii i   i  iii   i  i   i    `* Re: Command Languages Versus Programming Languages6Muttley
9 Apr 24 i ii i   i  iii   i  i   i     +- Re: Command Languages Versus Programming Languages1Kaz Kylheku
9 Apr 24 i ii i   i  iii   i  i   i     +- Re: Command Languages Versus Programming Languages1Janis Papanagnou
9 Apr 24 i ii i   i  iii   i  i   i     `* Re: Command Languages Versus Programming Languages3Muttley
9 Apr 24 i ii i   i  iii   i  i   i      `* Re: Command Languages Versus Programming Languages2John Ames
9 Apr 24 i ii i   i  iii   i  i   i       `- Re: Command Languages Versus Programming Languages1Muttley
8 Apr 24 i ii i   i  iii   i  i   +- [meta] Re: Command Languages Versus Programming Languages1Janis Papanagnou
10 Apr 24 i ii i   i  iii   i  i   `* Re: Command Languages Versus Programming Languages2Keith Thompson
10 Apr 24 i ii i   i  iii   i  i    `- Re: Command Languages Versus Programming Languages1Kenny McCormack
5 Apr 24 i ii i   i  iii   i  `* Re: Command Languages Versus Programming Languages47Janis Papanagnou
5 Apr 24 i ii i   i  iii   i   +* Re: Command Languages Versus Programming Languages27Stefan Ram
6 Apr 24 i ii i   i  iii   i   i+* Re: Command Languages Versus Programming Languages4Muttley
7 Apr 24 i ii i   i  iii   i   ii`* Re: Command Languages Versus Programming Languages3Lawrence D'Oliveiro
8 Apr 24 i ii i   i  iii   i   ii `* Re: Command Languages Versus Programming Languages2Muttley
9 Apr 24 i ii i   i  iii   i   ii  `- Re: Command Languages Versus Programming Languages1Lawrence D'Oliveiro
6 Apr 24 i ii i   i  iii   i   i+- Re: Command Languages Versus Programming Languages1Janis Papanagnou
6 Aug 24 i ii i   i  iii   i   i`* Re: Command Languages Versus Programming Languages21Sebastian
7 Aug 24 i ii i   i  iii   i   i `* Re: Command Languages Versus Programming Languages20Lawrence D'Oliveiro
7 Aug 24 i ii i   i  iii   i   i  +* Re: Command Languages Versus Programming Languages3Kaz Kylheku
8 Aug 24 i ii i   i  iii   i   i  +* Re: Command Languages Versus Programming Languages4Andreas Eder
25 Aug 24 i ii i   i  iii   i   i  `* Re: Command Languages Versus Programming Languages12Sebastian
5 Apr 24 i ii i   i  iii   i   +- Re: Command Languages Versus Programming Languages1Kaz Kylheku
6 Apr 24 i ii i   i  iii   i   `* Re: Command Languages Versus Programming Languages18Lawrence D'Oliveiro
3 Apr 24 i ii i   i  iii   `* Re: Command Languages Versus Programming Languages4David Brown
2 Apr 24 i ii i   i  ii`- Re: Command Languages Versus Programming Languages1Kaz Kylheku
2 Apr 24 i ii i   i  i`* Re: Command Languages Versus Programming Languages2Kaz Kylheku
2 Apr 24 i ii i   i  `* Re: Command Languages Versus Programming Languages20Lawrence D'Oliveiro
1 Apr 24 i ii i   `- Re: Command Languages Versus Programming Languages1Lawrence D'Oliveiro
1 Apr 24 i ii `- Re: Command Languages Versus Programming Languages1Andreas Eder
29 Mar 24 i i+- Re: Command Languages Versus Programming Languages1Christian Weisgerber
30 Mar 24 i i+* Re: Command Languages Versus Programming Languages2David Brown
30 Sep 24 i i`- Re: Command Languages Versus Programming Languages1Bozo User
29 Mar 24 i `- Re: Command Languages Versus Programming Languages1Kaz Kylheku
29 Mar 24 +* Re: Command Languages Versus Programming Languages554Johanne Fairchild
29 Mar 24 +* Re: Command Languages Versus Programming Languages2David Brown
29 Mar 24 +* Re: Command Languages Versus Programming Languages15Lawrence D'Oliveiro
30 Mar 24 +* Re: Command Languages Versus Programming Languages3Dmitry A. Kazakov
30 Sep 24 `* Re: Command Languages Versus Programming Languages4Bozo User

Haut de la page

Les messages affichés proviennent d'usenet.

NewsPortal