Print before-and-after bin numbers

[mnemon] / mnemon.c

diff --git a/mnemon.c b/mnemon.c
index 039f0ca0115325a6163018d47f1f1b68e53529a2..d28657bfe20d8a4c877bbbb30edf98d2694a74a7 100644 (file)
--- a/mnemon.c
+++ b/mnemon.c
@@ -21,6 +21,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdarg.h>
+#include <stdint.h>
 
 #include <sys/types.h>
 #include <dirent.h>
@@ -28,6 +29,11 @@
 #include <string.h>
 #include <assert.h>
 
+#include <readline/readline.h>
+#include <readline/history.h>
+
+typedef int bool_t;
+
 typedef struct _item {
     int count;
     char *challenge;
@@ -255,6 +261,18 @@ bin_add_item (bin_t        *bin,
     bin->items[bin->num_items++] = item;
 }
 
+static void
+bin_remove_item (bin_t *bin,
+                int     item_index)
+{
+    /* Replace the current item with the last item, (no need to shift
+     * any more than that since we don't care about the order of the
+     * items within a bin). */
+    bin->num_items--;
+    if (bin->num_items)
+       bin->items[item_index] = bin->items[bin->num_items];
+}
+
 static void
 mnemon_init (mnemon_t *mnemon)
 {
@@ -361,6 +379,16 @@ mnemon_get_bin (mnemon_t   *mnemon,
     return bin;
 }
 
+static void
+mnemon_remove_bin (mnemon_t    *mnemon,
+                  bin_t        *bin)
+{
+    int i = bin - mnemon->bins;
+
+    memmove (bin, bin + 1, (mnemon->num_bins - i) * sizeof (bin_t));
+    mnemon->num_bins--;
+}
+
 static void
 chomp (char *s)
 {
@@ -525,15 +553,133 @@ mnemon_save (mnemon_t *mnemon)
     }
 }
 
+/* Return a uniformly-distributed pseudo-random integer within the
+ * range:
+ *
+ *     0 <= result < num_values
+ */
+static int
+rand_within (int num_values)
+{
+    return (int) (num_values * (rand() / (RAND_MAX + 1.0)));
+}
+
+/* Return an exponentially-distributed pseudo-random integer within
+ * the range:
+ *
+ *     0 <= result < num_values
+ *
+ * The distribution is such that each successively larger value will
+ * occur with a probability of half of the previous value.
+ */
+static int
+rand_within_exponential (int num_values)
+{
+    static int r;
+    static uint32_t mask = 0;
+    int ones;
+    int bit;
+
+    /* Optimize the constant case. */
+    if (num_values == 1)
+       return 0;
+
+    ones = 0;
+
+    do {
+       if (mask == 0) {
+           r = rand ();
+           mask = 1 << 31;
+           while (mask > RAND_MAX)
+               mask >>= 1;
+       }
+       bit = r & mask;
+       mask >>= 1;
+       if (bit) {
+           ones++;
+           if (ones == num_values)
+               ones = 0;
+       }
+    } while (bit);
+
+    return ones;
+}
+
+static void
+mnemon_select_item (mnemon_t    *mnemon,
+                   bin_t       **bin_ret,
+                   int          *item_index_ret)
+{
+    int bin_index;
+    bin_t *bin;
+
+    bin_index = rand_within_exponential (mnemon->num_bins);
+
+    bin = &mnemon->bins[bin_index];
+
+    *bin_ret = bin;
+    *item_index_ret = rand_within (bin->num_items);
+}
+
+static void
+mnemon_do_challenges (mnemon_t *mnemon)
+{
+    bin_t *bin;
+    int item_index;
+    item_t *item;
+    char *response;
+    bool_t correct;
+
+    while (1) {
+       mnemon_select_item (mnemon, &bin, &item_index);
+       item = bin->items[item_index];
+
+       printf ("%s\n", item->challenge);
+
+       response = readline ("> ");
+       if (response == NULL) {
+           printf ("\n");
+           break;
+       }
+
+       correct = (strcmp (response, item->response) == 0);
+
+       bin_remove_item (bin, item_index);
+       if (bin->num_items == 0)
+           mnemon_remove_bin (mnemon, bin);
+
+       if (correct) {
+           printf ("Correct! (Moving from %d to ", item->count);
+           item->count++;
+           printf ("%d)\n\n", item->count);
+       } else {
+           printf ("  %s is the correct answer. (Moving from %d to ",
+                   item->response, item->count);
+           item->count--;
+           if (item->count > 0)
+               item->count = -1;
+           printf ("%d)\n\n", item->count);
+       }
+
+       bin = mnemon_get_bin (mnemon, item->count);
+
+       bin_add_item (bin, item);
+    }
+}
+
 int
 main (int argc, char *argv[])
 {
     mnemon_t mnemon;
 
+    srand (1);
+
     mnemon_init (&mnemon);
 
     mnemon_load (&mnemon);
 
+    mnemon_do_challenges (&mnemon);
+
     mnemon_save (&mnemon);
 
     mnemon_fini (&mnemon);