1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
|
#print
Of course, you can also search for lines that
contain backslashes; again, it's simply a matter
of doubling the backslash in the search pattern.
That is,
/\\/
finds the next line with a backslash.
Find the second occurrence of "\n\n" in the file
"prog.c", and type "answer N", where N is its
line number.
#create prog.c
int nsave = 0;
selunit()
{
char fnam[20], s[50];
static char dobuff[50];
char posslev[20][20];
int diff[20], i, k, m, n, best, alts, statb[20];
FILE *f;
char zb[200];
static char saved[20];
while (ask) {
printf("What lesson? ");
fflush(stdout);
gets(dobuff);
if (strcmp(dobuff, "bye") == 0)
wrapup(0);
level = todo = dobuff;
sprintf(s, "../L%s", dobuff);
if (access(s, 04) == 0)
return;
printf("no such lesson\n");
}
alts = 0;
retry:
f=scrin;
if (f==NULL) {
sprintf(fnam, "../L%s", level);
f = fopen(fnam, "r");
if (f==NULL) {
fprintf(stderr, "No script for lesson %s.\n", level);
wrapup(1);
}
while (fgets(zb, 200, f)) {
trim(zb);
if (strcmp(zb, "#next")==0)
break;
}
}
if (feof(f)) {
printf("Congratulations\n\n.You have finished this sequence.\n");
fflush(stdout);
todo = 0;
return;
}
for(i=0; fgets(s, 50, f); i++) {
sscanf(s, "%s %d", &posslev[i], &diff[i]);
}
best = -1;
/* cycle through lessons from random start */
/* first try the current place, failing that back up to
last place there are untried alternatives (but only one backup) */
n = grand()%i;
for(k=0; k<i; k++) {
m = (n+k)%i;
if (already(posslev[m])) continue;
if (best<0) best=m;
/* real alternatives */
alts++;
if (abs(diff[m]-speed) < abs(diff[best]-speed))
best=m;
}
if (best < 0 && nsave) {
nsave--;
strcpy(level, saved);
goto retry;
}
if (best <0) {
/* lessons exhausted or missing */
printf("Sorry, there are no alternative lessons at this stage.\n");
printf("See someone for help.\n\n");
fflush(stdout);
todo = 0;
return;
}
strcpy (dobuff, posslev[best]);
if (alts>1) {
nsave=1;
strcpy (saved, level);
}
todo = dobuff;
fclose(f);
}
abs(x)
{
return(x>=0? x: -x);
}
grand()
{
static int garbage;
int a[2], b;
time(a);
b = a[1]+10*garbage++;
return(b&077777);
}
#copyin
#user
#uncopyin
#match 73
#bad 43
The second______ one.
#log
#next
44.1h 10
|
