Interesting: I changed the write_felix procedure so that it calls a write_string wrapper that does a non-local goto to the end of the procedure on end of file: felix version of "exceptions" .. :)
But it is called by another procedure which also writes, so I then changed the write_felix procedure into a generator which returns the eof flag. The compiler then failed because I was doing a non-local goto in a function: this isn't allowed, non-local jumps can only be done in procedures. This is because Felix functions uses the machine stack, whilst procedures use linked heap allocated records, and non-local goto's have to unwind the stack to find the jump target. Unwinding is an active process which is required to NULL out return addresses so the garbage collector can reap unused procedure frames. Unwinding the machine stack is done differently: by throwing a C++ exception. There is some code which attempts to unwind across function/procedure boundaries by mixing the two techniques, but it isn't well defined or implemented: roughly speaking inside a function if you have a procedure stack you could unwind it, however the compiler generates a "micky mouse" version of flx_run to call procedures inside functions it's basically a one-liner: while(p)p=p->resume(); so such nested procedure calls can't really do non-local gotos to code OUTSIDE the function. Anyhow, the thing is that ordinary old generators (not ones with yields in them) merely look like functions: actually they're procedures. They're lifted out of expressions like x = a + g i; gives tmp = g i; x = a + tmp; and in that form there's no reason why we can't munge g into a procedure: var tmp; g_munged(&tmp, i); x = a + tmp; and now non-local gotos inside the generator should be ok because no it's a procedure :) -- john skaller skal...@users.sourceforge.net ------------------------------------------------------------------------------ Download new Adobe(R) Flash(R) Builder(TM) 4 The new Adobe(R) Flex(R) 4 and Flash(R) Builder(TM) 4 (formerly Flex(R) Builder(TM)) enable the development of rich applications that run across multiple browsers and platforms. Download your free trials today! http://p.sf.net/sfu/adobe-dev2dev _______________________________________________ Felix-language mailing list Felix-language@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/felix-language
