110 lines
2.1 KiB
C
110 lines
2.1 KiB
C
/**
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* See Copyright Notice in picrin.h
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*/
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#include "picrin.h"
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#include "../object.h"
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#include "../state.h"
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#if PIC_USE_CALLCC
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/*
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* [(reset e)]k = k ([e] halt ())
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* [(shift e)]k = [e] halt (\c x, c (k x))
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*/
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static pic_value
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pic_cont_reset(pic_state *pic)
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{
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pic_value thunk;
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pic_get_args(pic, "l", &thunk);
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return pic_call(pic, thunk, 0);
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}
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static pic_value
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shift_call(pic_state *pic)
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{
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pic_value x;
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struct context cxt;
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pic_get_args(pic, "o", &x);
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CONTEXT_INIT(pic, &cxt, pic_closure_ref(pic, 0), 1, &x);
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pic_vm(pic, &cxt);
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return pic_protect(pic, cxt.fp->regs[1]);
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}
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static pic_value
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pic_cont_shift(pic_state *pic)
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{
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pic_value f, k;
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pic_get_args(pic, "l", &f);
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k = pic_lambda(pic, shift_call, 1, pic->cxt->fp->regs[1]);
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CONTEXT_INITK(pic, pic->cxt, f, pic->halt, 1, &k);
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return pic_invalid_value(pic);
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}
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static pic_value
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cont_call(pic_state *pic)
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{
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int argc;
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pic_value *argv, k, dyn_env;
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struct context *cxt, *c;
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pic_get_args(pic, "*", &argc, &argv);
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cxt = pic_data(pic, pic_closure_ref(pic, 0));
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k = pic_closure_ref(pic, 1);
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dyn_env = pic_closure_ref(pic, 2);
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/* check if continuation is alive */
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for (c = pic->cxt; c != NULL; c = c->prev) {
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if (c == cxt) {
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break;
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}
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}
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if (c == NULL) {
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pic_error(pic, "calling dead escape continuation", 0);
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}
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CONTEXT_INIT(pic, cxt, k, argc, argv);
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pic->cxt = cxt;
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pic->dyn_env = dyn_env;
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longjmp(cxt->jmp, 1);
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PIC_UNREACHABLE();
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}
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pic_value
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pic_make_cont(pic_state *pic, pic_value k)
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{
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static const pic_data_type cxt_type = { "cxt", NULL };
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return pic_lambda(pic, cont_call, 3, pic_data_value(pic, pic->cxt, &cxt_type), k, pic->dyn_env);
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}
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static pic_value
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pic_cont_callcc(pic_state *pic)
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{
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pic_value f;
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pic_get_args(pic, "l", &f);
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return pic_callk(pic, f, 1, pic_make_cont(pic, pic->cxt->fp->regs[1]));
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}
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void
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pic_init_cont(pic_state *pic)
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{
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pic_defun(pic, "call-with-current-continuation", pic_cont_callcc);
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pic_defun(pic, "call/cc", pic_cont_callcc);
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pic_defun(pic, "shift", pic_cont_shift);
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pic_defun(pic, "reset", pic_cont_reset);
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}
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#endif /* PIC_USE_CALCC */
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