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72 lines
3 KiB
C
72 lines
3 KiB
C
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2022 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/log/check.h"
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#include "tool/plinko/lib/index.h"
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#include "tool/plinko/lib/plinko.h"
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/**
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* Counts references to variable.
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*
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* @param v is atom name of variable
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* @param m is count after which we should stop counting
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* @param e is expression
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* @return number of counted references greater than zero
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* @note this produces garbage when recursing into let
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*/
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int CountReferences(int v, int m, int e) {
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int f, r;
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DCHECK_GT(v, 0);
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if (e >= 0) {
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r = e == v;
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} else {
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f = Car(e);
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if (f == kQuote || f == kClosure) {
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r = 0;
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} else if (f == kLambda || f == kMacro) {
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if (m > 0 && !HasAtom(v, Cadr(e))) {
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r = CountReferences(v, m, Caddr(e));
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} else {
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r = 0;
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}
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} else if (f == kCond) {
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for (r = 0; (e = Cdr(e)) < 0 && r < m;) {
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if ((f = Car(e)) < 0) {
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r += CountReferences(v, m - r, Car(f));
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if ((f = Cdr(f)) < 0) {
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r += CountReferences(v, m - r, Car(f));
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}
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}
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}
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} else {
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for (r = 0; e && r < m;) {
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if (e < 0) {
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f = Car(e);
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e = Cdr(e);
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} else {
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f = e;
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e = 0;
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}
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r += CountReferences(v, m - r, f);
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}
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}
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}
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DCHECK_GE(r, 0);
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return r;
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}
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