text: #include "libbracket.h"
  
  int isalpha(int c) {
  	return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z');
  }
  
  int isdigit(int c) {
  	return c >= '0' && c <= '9';
  }
  
  int isalnum(int c) {
  	return isdigit(c) || isalpha(c);
  }
  
  int toupper(int c) {
  	if (c >= 'A' && c <= 'Z') {
  		return c | 32;
  	} else {
  		return c;
  	}
  }
  
  int tolower(int c) {
  	if (c >= 'a' && c <= 'z') {
  		return c & ~32;
  	} else {
  		return c;
  	}
  }
  