[TUHS] v7 K&R C

scj at yaccman.com scj at yaccman.com
Mon May 11 10:28:04 AEST 2020

Following up on Rob's comment, I always took the point of view that
Dennis owned the C description, and what he said goes.  Not that I
didn't make suggestions that he accepted.  One of the better ones
(actually in B) was ^ for exclusive OR.  One of the worse ones was the
syntax for casts.  We looked at about 5 different ideas and hated all of
them.   And most of them couldn't be easily compiled with Yacc.  So I
took the grammar for declarations, removed the variable name, and voila,
it expressed everything we wanted in the way of semantics, had a simple
rule of construction, and we badly needed the functionality for the
Interdata port.   I quickly came to hate it, though -- the casts we were
using looked like a teletype threw up in the middle of the code. 

With respect to enums, there is a feature I've wanted for years: a typed
typedef.  Saying typetdef int foo would make foo an integer, but if you
passed an ordinary int to something declared as foo it would be an
error.  Even if it was an integer constant unless cast. 

The amount of mechanism required to get that behavior from both C and
C++ is horrible, so far as I know, although C++ has accreted so much
stuff maybe it's there now... 



On 2020-04-24 19:54, Rob Pike wrote:

> Another debate at the time was caused by a disagreement between pcc and cc regarding enums: are they a type or just a way to declare constant? I remember getting annoyed by pcc not letting me declare a constant with an enum and use it as an int. I protested to scj and dmr and after some to-ing and fro-ing Steve changed pcc to treat them as constants. 
> Not sure it was the right decision, but C desperately wanted a non-macro way to define a constant. I'd probably argue the same way today. The real lesson is how propinquity affects progress. 
> -rbo 
> On Sat, Apr 25, 2020 at 12:51 PM Rob Pike <robpike at gmail.com> wrote: 
> The ability to call a function pointer fp with the syntax fp() rather than (*fp)() came rather late, I think at Bjarne's suggestion or example. Pretty sure it was not in v7 C, as you observe. 
> Convenient though the shorthand may be, it always bothered me as inconsistent and misleading. (I am pretty sure I used it sometimes regardless.)
> -rob 
> On Sat, Apr 25, 2020 at 12:48 PM Adam Thornton <athornton at gmail.com> wrote: 
> On Apr 24, 2020, at 7:37 PM, Charles Anthony <charles.unix.pro at gmail.com> wrote: 
> On Fri, Apr 24, 2020 at 7:00 PM Adam Thornton <athornton at gmail.com> wrote: 
> This doesn't like the function pointer. 
> $ cc -c choparg.c 
> choparg.c:11: Call of non-function 
> Perhaps: 
> (*fcn)(arg);

We have a winner! 

Also, Kartik, dunno where it is on the net, but if you install a v7
system, /usr/src/cmd/c 

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