some demos from class, should have checked in earlier

bitwise/bitwise.c

+#include <stdio.h>
+
+void print_byte(unsigned char b) {
+  for (int shift=7; shift >=0; shift--) {
+    // xxxxxxxx &
+    // 10000000
+    // x0000000 --> 0000000x
+    // we call this "masking"
+    printf("%d", (b & (1 << shift)) >> shift);
+  }
+  printf("\n");
+}
+
+int main(void) {
+
+  // high four bits are set
+  // 11110000
+  unsigned char number_a = 0xF0;
+
+  // biggest number you can represent in the lower nibble of a byte; low four
+  // bits are set.
+  // 00001111
+  unsigned char number_b = 0x0F;
+
+
+  // 11110000 &
+  // 00001111
+  // 00000000
+  printf("%d\n", (number_a & number_b));
+
+  // 11110000 |
+  // 00001111
+  // 00000000
+  printf("%d\n", (number_a | number_b));
+
+  print_byte(number_a);
+  print_byte(~number_a);
+  print_byte(number_b);
+
+  printf("%d\n", (unsigned char)~number_a);
+  // printf("%d\n", number_b);
+
+  printf("%d\n", (unsigned char)(~number_a) == number_b);
+
+  // print_byte(0);
+  //print_byte(7);
+
+  return 0;
+}

regex/regex.c

+#include <sys/types.h>
+#include <regex.h>
+#include <stdio.h>
+
+int main(void) {
+
+  regex_t reg;
+
+  regcomp(&reg, "^..b.m$", 0);
+
+  int result = regexec(&reg, "album", 0, NULL, 0);
+  printf("what was the result? 0 for success: %d\n", result);
+
+  result = regexec(&reg, "something that doesn't contain the pattern", 0, NULL, 0);
+  printf("what was the result? 0 for success: %d\n", result);
+
+  result = regexec(&reg, "album of the year", 0, NULL, 0);
+  printf("what was the result? 0 for success: %d\n", result);
+
+  return 0;
+}