146 lines
4.2 KiB
C
146 lines
4.2 KiB
C
/*-*- 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 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ This program is free software; you can redistribute it and/or modify │
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│ it under the terms of the GNU General Public License as published by │
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│ the Free Software Foundation; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ WITHOUT ANY WARRANTY; without even the implied warranty of │
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│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
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│ General Public License for more details. │
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│ │
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│ You should have received a copy of the GNU General Public License │
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│ along with this program; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/runtime/runtime.h"
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#include "libc/stdio/stdio.h"
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#define T short
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#define CONS 0
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#define ATOM 1
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#define INTEGER 2
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#define NIL OBJECT(CONS, 0)
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#define TYPE(x) ((x)&3)
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#define VALUE(x) ((x) >> 2)
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#define OBJECT(t, v) ((v) << 2 | (t))
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static T Mi, Si;
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static T M[2048];
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static char S[2048];
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static noreturn void Die(void) {
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abort();
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}
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static int Parse(const char *s) {
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int x, j;
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for (;;) {
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switch (*s & 0xff) {
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case ' ':
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case '\t':
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case '\r':
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case '\n':
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case '\v':
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++s;
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break;
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case 'A' ... 'Z':
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x = Si;
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do {
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S[Si++] = *s++;
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} while ('A' <= *s && *s <= 'Z');
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S[Si++] = 0;
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M[++Mi] = OBJECT(ATOM, x);
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return Mi;
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case '0' ... '9':
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x = 0;
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do {
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x *= 10;
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x += *s++ - '0';
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} while ('0' <= *s && *s <= '9');
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M[++Mi] = OBJECT(INTEGER, x);
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return Mi;
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default:
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Die();
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}
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}
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}
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static int PrintChar(int c) {
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return putc(c, stdout);
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}
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static void PrintString(const char *s) {
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while (*s) PrintChar(*s++);
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}
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static void PrintInteger(int x) {
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int q, r;
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q = x / 10;
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r = x % 10;
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if (q) PrintInteger(q);
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PrintChar('0' + r);
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}
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static void PrintObject(int i) {
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int j, x;
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switch (TYPE(M[i])) {
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case CONS:
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if ((i = VALUE(M[i]))) {
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PrintChar('(');
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PrintObject(i);
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for (;;) {
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if (TYPE(M[i + 1]) == CONS) {
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if (!(i = VALUE(M[i + 1]))) break;
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PrintChar(' ');
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PrintObject(i);
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} else {
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PrintString(" . ");
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PrintObject(i + 1);
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break;
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}
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}
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PrintChar(')');
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} else {
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PrintString("NIL");
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}
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break;
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case ATOM:
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for (j = VALUE(M[i]); S[j]; ++j) {
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PrintChar(S[j]);
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}
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break;
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case INTEGER:
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PrintInteger(VALUE(M[i]));
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break;
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default:
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unreachable;
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}
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}
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static void Print(int i) {
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PrintObject(i);
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PrintChar('\n');
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}
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int main(int argc, char *argv[]) {
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int i;
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M[1] = OBJECT(CONS, 2);
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M[2] = OBJECT(INTEGER, 123);
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M[3] = OBJECT(CONS, 4);
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M[4] = OBJECT(INTEGER, 456);
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M[5] = OBJECT(CONS, 6);
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M[6] = OBJECT(INTEGER, 789);
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M[7] = NIL;
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Print(1);
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return 0;
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}
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