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From: David Brown <david.brown@hesbynett.no>
Newsgroups: comp.lang.c
Subject: Re: else ladders practice
Date: Tue, 5 Nov 2024 17:02:04 +0100
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On 05/11/2024 16:03, Bart wrote:
> On 05/11/2024 12:42, Waldek Hebisch wrote:
>> Bart <bc@freeuk.com> wrote:
>>>
>>> Then we disagree on what 'multi-way' select might mean. I think it means
>>> branching, even if notionally, on one-of-N possible code paths.
>>
>> OK.
>>> The whole construct may or may not return a value. If it does, then one
>>> of the N paths must be a default path.
>>
>>
>> You need to cover all input values.  This is possible when there
>> is reasonably small number of possibilities.  For example, switch on
>> char variable which covers all possible values does not need default
>> path.  Default is needed only when number of possibilities is too
>> large to explicitely give all of them.  And some languages allow
>> ranges, so that you may be able to cover all values with small
>> number of ranges.
>>
> 
> What's easier to implement in a language: to have a conditional need for 
> an 'else' branch, which is dependent on the compiler performing some 
> arbitrarily complex levels of analysis on some arbitrarily complex set 
> of expressions...
> 
> ...or to just always require 'else', with a dummy value if necessary?

If this was a discussion on learning about compiler design for newbies, 
that might be a relevant point.  Otherwise, what is easier to implement 
in a language tool is completely irrelevant to what is good in a language.

A language should try to support things that are good for the 
/programmer/, not the compiler.  But it does have to limited by what is 
practically possible for a compiler.  A fair bit of the weaknesses of C 
as a language can be attributed to the limitations of compilers from its 
early days, and thereafter existing practice was hard to change.