77 lines
2.2 KiB
C
77 lines
2.2 KiB
C
/* promise.c: Delay and force.
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*
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* $Id$
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*
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* Copyright 1990, 1991, 1992, 1993, 1994, 1995, Oliver Laumann, Berlin
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* Copyright 2002, 2003 Sam Hocevar <sam@hocevar.net>, Paris
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*
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* This software was derived from Elk 1.2, which was Copyright 1987, 1988,
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* 1989, Nixdorf Computer AG and TELES GmbH, Berlin (Elk 1.2 has been written
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* by Oliver Laumann for TELES Telematic Services, Berlin, in a joint project
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* between TELES and Nixdorf Microprocessor Engineering, Berlin).
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*
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* Oliver Laumann, TELES GmbH, Nixdorf Computer AG and Sam Hocevar, as co-
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* owners or individual owners of copyright in this software, grant to any
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* person or company a worldwide, royalty free, license to
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*
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* i) copy this software,
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* ii) prepare derivative works based on this software,
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* iii) distribute copies of this software or derivative works,
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* iv) perform this software, or
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* v) display this software,
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*
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* provided that this notice is not removed and that neither Oliver Laumann
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* nor Teles nor Nixdorf are deemed to have made any representations as to
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* the suitability of this software for any purpose nor are held responsible
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* for any defects of this software.
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*
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* THERE IS ABSOLUTELY NO WARRANTY FOR THIS SOFTWARE.
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*/
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#include "config.h"
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#include "kernel.h"
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Object P_Promisep (Object x) {
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return TYPE(x) == T_Promise ? True : False;
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}
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Object P_Delay (Object argl) {
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Object d;
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GC_Node;
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GC_Link (argl);
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d = Alloc_Object (sizeof (struct S_Promise), T_Promise, 0);
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GC_Unlink;
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PROMISE(d)->done = 0;
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PROMISE(d)->env = The_Environment;
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PROMISE(d)->thunk = Car (argl);
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return d;
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}
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Object P_Force (Object d) {
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Object ret, a[2];
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GC_Node;
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TC_Prolog;
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Check_Type (d, T_Promise);
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if (PROMISE(d)->done)
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return PROMISE(d)->thunk;
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GC_Link (d);
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a[0] = PROMISE(d)->thunk; a[1] = PROMISE(d)->env;
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TC_Disable;
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ret = P_Eval (2, a);
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TC_Enable;
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GC_Unlink;
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if (PROMISE(d)->done) /* take care of recursive force calls */
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return PROMISE(d)->thunk;
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PROMISE(d)->thunk = ret;
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PROMISE(d)->done = 1;
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return ret;
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}
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Object P_Promise_Environment (Object p) {
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Check_Type (p, T_Promise);
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return PROMISE(p)->env;
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}
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