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From: fir <fir@grunge.pl>
Newsgroups: comp.lang.c
Subject: Re: else ladders practice
Date: Sat, 09 Nov 2024 11:08:05 +0100
Organization: i2pn2 (i2pn.org)
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To: Bart <bc@freeuk.com>
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Bart wrote:
> On 06/11/2024 07:26, Kaz Kylheku wrote:
>> On 2024-11-05, Bart <bc@freeuk.com> wrote:
>
>>> Well, it started off as 2-way select, meaning constructs like this:
>>>
>>>      x = c ? a : b;
>>>      x := (c | a | b)
>>>
>>> Where one of two branches is evaluated. I extended the latter to N-way
>>> select:
>>>
>>>      x := (n | a, b, c, ... | z)
>>
>> This looks quite error-prone. You have to count carefully that
>> the cases match the intended values. If an entry is
>> inserted, all the remaining ones shift to a higher value.
>>
>> You've basically taken a case construct and auto-generated
>> the labels starting from 1.
>
> It's a version of Algol68's case construct:
>
>     x := CASE n IN a, b, c OUT z ESAC
>
> which also has the same compact form I use. I only use the compact
> version because n is usually small, and it is intended to be used within
> an expression: print (n | "One", "Two", "Three" | "Other").
>
> This an actual example (from my first scripting language; not written by
> me):
>
>       Crd[i].z := (BendAssen |P.x, P.y, P.z)
>
> An out-of-bounds index yields 'void' (via a '| void' part inserted by
> the compiler). This is one of my examples from that era:
>
>    xt := (messa | 1,1,1, 2,2,2, 3,3,3)
>    yt := (messa | 3,2,1, 3,2,1, 3,2,1)
>

still the more c compatimle version would look better imo

     xt =  {1,1,1, 2,2,2, 3,3,3}[messa];
     yt =  {3,2,1, 3,2,1, 3,2,1}[messa];

esp if maybe there would be allowed to also use [] leftside

and

     t =  {1,3, 1,2, 1,1 2,3, 2,2, 2,1, 3,3, 3,2, 3,1} [messa]

where t is struct {x,y}

could be maybe faster


> Algol68 didn't have 'switch', but I do, as well as a separate
> case...esac statement that is more general. Those are better for
> multi-line constructs.
>
> As for being error prone because values can get out of step, so is a
> function call like this:
>
>     f(a, b, c, d, e)
>
> But I also have keyword arguments.
>