Fix masks

They need to zero out everything *except* the bits containing the mask,
which means they need to be as wide as the shift, and filled with ones.

scm/inc/driver.c

@@ -6,12 +6,12 @@
#define fixnum_tag   0 // 00
#define fixnum_shift 2
#define char_mask 240  // 11110000
#define char_tag  15   // 00001111
#define char_mask 0xff  // 11111111
#define char_tag  15    // 00001111
#define char_shift 8
#define boolean_mask  96 // 1100000
#define boolean_tag   31 // 0011111
#define boolean_mask  0x3f // 1111111
#define boolean_tag   31   // 0011111
#define boolean_shift 7
#define empty_list   47 // 00101111
@@ -22,9 +22,9 @@ int main(int argc, char **argv) {
	int val = scheme_entry();
	if ((val & fixnum_mask) == fixnum_tag) {
		printf("%d\n", val >> fixnum_shift);
	} else if ((val & char_mask) == 0) {
	} else if ((val & char_mask) == char_tag) {
		printf("#\\%c\n", val >> char_shift);
	} else if ((val & boolean_mask) == 0) {
	} else if ((val & boolean_mask) == boolean_tag) {
		printf("#%s\n", (val >> boolean_shift) == 1 ? "t" : "f");
	} else if (val == empty_list) {
		printf("()\n");