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%{
#include <err.h>
#include <getopt.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define YY_USER_ACTION ECHO;
const char empty_field[] = "argument to the -p option contains an empty field";
const char invalid_char[] = "argument to the -p option must be a "
"comma-seperated list of positive integers";
const char final_comma[] = "argument to the -p option contains trailing comma";
const char *argv0;
unsigned pos;
struct {
unsigned *ps;
size_t len;
} positions;
static void usage(void);
static void append_positions(char *s);
static int ucmp(const void *, const void *);
static unsigned atou(const char *);
static bool print_ordinal(void);
%}
%option nodefault noinput nounput
%%
[0-9]*(1[0-9]|[04-9]) { pos++; if (print_ordinal()) fputs("th", stdout); }
[0-9]*1 { pos++; if (print_ordinal()) fputs("st", stdout); }
[0-9]*2 { pos++; if (print_ordinal()) fputs("nd", stdout); }
[0-9]*3 { pos++; if (print_ordinal()) fputs("rd", stdout); }
\n { pos = 0; }
[^0-9\n]+ ;
%%
void
usage(void)
{
fprintf(stderr, "Usage: %s [-p indicies ...] [file ...]\n", argv0);
exit(EXIT_FAILURE);
}
int
main(int argc, char **argv)
{
int opt, rv;
struct option longopts[] = {
{"positions", required_argument, 0, 'p'},
{ NULL, 0, 0, 0 }
};
argv0 = argv[0];
rv = EXIT_SUCCESS;
while ((opt = getopt_long(argc, argv, "p:", longopts, NULL)) != -1) {
switch (opt) {
case 'p':
append_positions(optarg);
break;
default:
usage();
}
}
argc -= optind;
argv += optind;
if (argc == 0)
yylex();
for (int i = 0; i < argc; i++) {
if (strcmp(argv[i], "-") == 0)
yyin = stdin;
else if ((yyin = fopen(argv[i], "r")) == NULL) {
warn("fopen: %s", argv[i]);
rv = EXIT_FAILURE;
continue;
}
yylex();
if (yyin != stdin)
fclose(yyin);
}
return rv;
}
void
append_positions(char *raw)
{
bool comma = true;
const char *s;
if (positions.ps != NULL) {
warnx("the -p option should only be provided once");
usage();
}
for (s = raw, positions.len++; *s; s++) {
switch (*s) {
case ',':
if (comma)
errx(EXIT_FAILURE, empty_field);
comma = true;
positions.len++;
break;
case '0': case '1': case '2': case '3': case '4':
case '5': case '6': case '7': case '8': case '9':
comma = false;
break;
default:
errx(EXIT_FAILURE, invalid_char);
}
}
if (comma == true)
errx(EXIT_FAILURE, final_comma);
if ((positions.ps = malloc(sizeof(unsigned *) * positions.len)) == NULL)
err(EXIT_FAILURE, "malloc");
/* Iterate over each position, parse it, and sort the results. It’s
safe to use strtok() and atou() here since the input string has been
pre-validated. */
s = strtok(raw, ",");
for (size_t i = 0; s != NULL; i++) {
positions.ps[i] = atou(s);
s = strtok(NULL, ",");
}
qsort(positions.ps, positions.len, sizeof(unsigned), ucmp);
}
int
ucmp(const void *a, const void *b)
{
unsigned a_ = *(unsigned *)a,
b_ = *(unsigned *)b;
return a_ > b_ ? 1 : b_ < a_ ? -1 : 0;
}
unsigned
atou(const char *s)
{
unsigned n = 0;
for (; *s; s++)
n = n * 10 + *s - '0';
return n;
}
bool
print_ordinal(void)
{
if (positions.ps == NULL)
return true;
/* Basic binary search */
for (ssize_t l = 0, r = positions.len - 1, m; l <= r;) {
m = l + (r - l) / 2;
if (positions.ps[m] == pos)
return true;
if (positions.ps[m] > pos)
r = m - 1;
else
l = m + 1;
}
return false;
}
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