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From: Bart <bc@freeuk.com>
Newsgroups: comp.lang.c
Subject: Re: how to make a macro work as a single line if stmt without braces
Date: Tue, 24 Sep 2024 21:12:28 +0100
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On 24/09/2024 20:59, Kaz Kylheku wrote:
> On 2024-09-24, Bart <bc@freeuk.com> wrote:
>> (Maybe the language needs a construct like 'elif', as is used in
> 
> The language doesn't need such a construct in order for a compiler
> to implement it internally.
> 
> You just have to treat the token sequence   else if  as a supertoken.
> 
> Doing it at the grammar level may require two symbols of lookahead,
> which is a a problem for off-the-shelf parser generation tooling based
> on LALR(1) and whatnot.

That sounds as much of a hack as making a special case for 'else if' so 
that it doesn't need 'else {if' (and a matching } later on) when 
enforcing compound statements for such blocks.

One consequence of how it works now is that if I write:

     if (a) {}
     else if (b) {}
     else if (c) {}
     else {}

then use a tool I have to visualise C code in my syntax, it generates:

     if a then
     else
         if b then
         else
             if c then
             else
             fi
         fi
     fi

The nested nature is revealed. If there were 50 'else if' links, the 
output would disappear off to the right.

With elif, elsif etc, the compiler has the option to keep the internal 
structure linear (which also means it will not put pressure on the stack 
if somebody decides to write a million of them).