🚀 go-pugleaf

jwil1@cs.aukuni.ac.nz (TMOTA) writes:
>torbenm@diku.dk (Torben AEgidius Mogensen) writes:
>
>>Afeature I have sorely missed in compilers for C etc. is a cheap
>>tail-call: if the last thing you do in a procedure or function is to
>>call a procedure or function, this can be implemented as a goto rather
>>than a general procedure/function call.
>
>What do you mean? What if the tail-called function then tries to call
>another function or (even worse) recurses? This could only work if
>the tail-called function expected to recieve *exactly* the stack frame
>that the tail-caller has had set up when it was called.

Maybe my brain has been rotted by using HPs for too long, but I'm sure
that Norcroft C does tail call optimization (I'll give my Arc a break
from being a Tertis and Icon server some time, and check it).
Certainly lots of compilers (OK, I mean gcc) do it, and manage the
necessary frame fiddling.

It's occasionally useful for writing gross/cute things like:

int countBits (int i, int acc)
{
    return i == 0 ? acc : countBits (i & (i - 1), acc + 1);
}

(doubtless originally due to Martin Richards :-) I think Norcroft
produces near identical code for the above and an equivalent explicit
loop.

On designing languages in general, if you're trying to produce a fast
system language you could try something a bit like B (typeless C +/- a
bit), which would be fun. Once you start integrating all those
wonderful little features you love from Lisp and Icon and Eiffel et
al, you tend to lose some of the elegance and simplicity you meant to
achieve :-)

Cheers,
Charlie

Anything approximating an opinion is my own
and is not necessarily shared by my company