Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.unix.shell,comp.unix.programmer,comp.lang.misc
Subject: Re: Command Languages Versus Programming Languages
Date: Wed, 03 Apr 2024 12:58:49 -0700
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David Brown <david.brown@hesbynett.no> writes:
> On 03/04/2024 19:19, Keith Thompson wrote:
>> David Brown <david.brown@hesbynett.no> writes:
>>> On 03/04/2024 18:00, Keith Thompson wrote:
>>>> David Brown <david.brown@hesbynett.no> writes:
>> [...]
>>>>> That's probably the reason almost no one uses it.  That post is the
>>>>> first time I have ever seen conditional expressions outside of a brief
>>>>> mention in a tutorial on Python conditionals showing how to write
>>>>> normal conditionals in the language.  I think Python stole this one
>>>>> from Perl.
>>>> No, Perl's conditional expressions use the same syntax as C's.
>>>
>>> I am not very familiar with Perl, and don't know what are expressions
>>> or statements.  Perhaps I have been imagining things.  I had the idea
>>> that in Perl you could write "<do_this> if <condition>" as an
>>> alternative to the more common imperative language ordering "if
>>> <condition> then <do_this>".
>> Yes, but it's not the same thing.  Perl has postfix conditionals, so
>> you
>> can write:
>>      statement if condition;
>> but that's a statement, not an expression, and there's no form
>> equivalent to if/else.  It's a specific case of "statement modifiers",
>> where the keyword can be any of if, unless, while, until, for, foreach,
>> or when.  (The latter is for an experimental "switch" feature, disabled
>> by default in recent releases.)
>
> OK.  That's a lot more than I knew.
>
> However, I don't see a relevant distinction between a statement and an
> expression as particularly significant here, at least in terms of code 
> clarity.

One distinction is that, for example, you can't use
    statement if condition;
as part of a larger expression.  Also, there's no else clause.

Perl's statement modifiers are an alternative syntax for conditional
*statements*.  In particular, `statement if condition;` is equivalent to
`if (condition) { statement; }`.  Their purpose is to allow some code to
be written more concisely.  (Note that an if statement or other compound
statement requires { and }.)

Perl adopted C's ?: syntax for conditional expressions with little or
no change.

[...]

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Medtronic
void Void(void) { Void(); } /* The recursive call of the void */