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/* Copyright (C) 2019 C. McEnroe <june@causal.agency>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <err.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysexits.h>
#include <time.h>
enum {
Cols = 80,
Rows = 25,
};
static char page[Rows][Cols];
static char get(int y, int x) {
if (y < 0 || y >= Rows) return 0;
if (x < 0 || x >= Cols) return 0;
return page[y][x];
}
static void put(int y, int x, char v) {
if (y < 0 || y >= Rows) return;
if (x < 0 || x >= Cols) return;
page[y][x] = v;
}
enum { StackLen = 1024 };
static long stack[StackLen];
static size_t top = StackLen;
static void push(long val) {
if (!top) errx(EX_SOFTWARE, "stack overflow");
stack[--top] = val;
}
static long pop(void) {
if (top == StackLen) return 0;
return stack[top++];
}
static struct {
int y, x;
int dy, dx;
} pc = { .dx = 1 };
static void inc(void) {
pc.y += pc.dy;
pc.x += pc.dx;
if (pc.y == -1) pc.y += Rows;
if (pc.x == -1) pc.x += Cols;
if (pc.y == Rows) pc.y -= Rows;
if (pc.x == Cols) pc.x -= Cols;
}
static bool string;
static bool step(void) {
char ch = page[pc.y][pc.x];
if (ch == '"') {
string ^= true;
} else if (string) {
push(ch);
inc();
return true;
}
if (ch == '?') ch = "><^v"[rand() % 4];
long x, y, v;
switch (ch) {
break; case '+': push(pop() + pop());
break; case '-': y = pop(); x = pop(); push(x - y);
break; case '*': push(pop() * pop());
break; case '/': y = pop(); x = pop(); push(x / y);
break; case '%': y = pop(); x = pop(); push(x % y);
break; case '!': push(!pop());
break; case '`': y = pop(); x = pop(); push(x > y);
break; case '>': pc.dy = 0; pc.dx = +1;
break; case '<': pc.dy = 0; pc.dx = -1;
break; case '^': pc.dy = -1; pc.dx = 0;
break; case 'v': pc.dy = +1; pc.dx = 0;
break; case '_': pc.dy = 0; pc.dx = (pop() ? -1 : +1);
break; case '|': pc.dx = 0; pc.dy = (pop() ? -1 : +1);
break; case ':': x = pop(); push(x); push(x);
break; case '\\': y = pop(); x = pop(); push(y); push(x);
break; case '$': pop();
break; case '.': printf("%ld ", pop()); fflush(stdout);
break; case ',': printf("%c", (char)pop()); fflush(stdout);
break; case '#': inc();
break; case 'g': y = pop(); x = pop(); push(get(y, x));
break; case 'p': y = pop(); x = pop(); v = pop(); put(y, x, v);
break; case '&': x = EOF; scanf("%ld", &x); push(x);
break; case '~': push(getchar());
break; case '@': return false;
break; default: if (ch >= '0' && ch <= '9') push(ch - '0');
}
inc();
return true;
}
int main(int argc, char *argv[]) {
srand(time(NULL));
memset(page, ' ', sizeof(page));
FILE *file = stdin;
if (argc > 1) {
file = fopen(argv[1], "r");
if (!file) err(EX_NOINPUT, "%s", argv[1]);
}
int y = 0;
char *line = NULL;
size_t cap = 0;
while (y < Rows && 0 < getline(&line, &cap, file)) {
for (int x = 0; x < Cols; ++x) {
if (line[x] == '\n' || !line[x]) break;
page[y][x] = line[x];
}
y++;
}
free(line);
while (step());
return pop();
}
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