fusl/src/ctype/isalpha.c

#include <ctype.h>
#include "libc.h"
#undef isalpha

int isalpha(int c) {
  return ((unsigned)c | 32) - 'a' < 26;
}

int __isalpha_l(int c, locale_t l) {
  return isalpha(c);
}

weak_alias(__isalpha_l, isalpha_l);