This page is part of the web mail archives of SRFI 50 from before July 7th, 2015. The new archives for SRFI 50 contain all messages, not just those from before July 7th, 2015.
Jim Blandy wrote:
In Pika:
- Forgetting an UNGCPRO corrupts the GC's data structures, and may
fail only intermittently. Irregular exits (return; goto; break;
continue) require attention. longjmp is even harder.
- Functions may only return Scheme values by reference; they may not
provide them as their (syntactic) return values. Instead of writing
"f (g (x))", you must write:
g (&frame.x, &frame.temp);
f (&frame.temp, &frame.temp2);
In other words, you must write your code as linear series of
operations which work by side-effects.
- Since the API functions all expect pointers to t_scm_word values,
this discourages people from passing them around directly, but it
can still be done --- e.g. "frame.x = frame.y;" --- and doing so
will usually work. But doing so is a bug.
- Variable declarations are cluttered with enclosing structs and GCPRO
/ UNGCPRO calls.
This of course cries out for a C++ interface which can alleviate
these problems:
class ScmVal
{
void *ref;
~ScmVal() { UNGCPRO(ref); }
... copy constructor etc ...;
}
Then f(g(x)) becomes:
f(g(x))
assuming:
ScmVal g (ScmVal x) { ... }
--
--Per Bothner
per@xxxxxxxxxxx http://per.bothner.com/