From 640321106d0b60f1f9ed408537691b90a768a651 Mon Sep 17 00:00:00 2001
From: Carl Worth <cworth@cworth.org>
Date: Tue, 17 Apr 2007 10:37:40 -0700
Subject: [PATCH] Add interactive querying of items
We select a bin with an expoentially-distributed pseudo-random number,
(so the items that have been misses the most get the most repetition),
then select an item within that bin with a uniformly distributed
random number. After querying the user, the item's count is adjusted
to the next higher/lower positive/negative number if the user's
response is correct/incorrect. And the item is moved into the new
bin based on its count.
---
Makefile | 3 +-
mnemon.c | 134 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 136 insertions(+), 1 deletion(-)
diff --git a/Makefile b/Makefile
index dbb41d5..238afe1 100644
--- a/Makefile
+++ b/Makefile
@@ -1,10 +1,11 @@
MY_CFLAGS=-Wall -Wextra -Wmissing-prototypes -Wno-unused-parameter -Wno-sign-compare
+MY_LDFLAGS=-lreadline
PROGRAMS=mnemon
all: $(PROGRAMS)
%: %.o
- $(CC) $(CFLAGS) $(MY_CFLAGS) $(LDFLAGS) -o $@ $^
+ $(CC) $(CFLAGS) $(MY_CFLAGS) $(LDFLAGS) $(MY_LDFLAGS) -o $@ $^
%.o: %.c
$(CC) $(CFLAGS) $(MY_CFLAGS) -c -o $@ $<
diff --git a/mnemon.c b/mnemon.c
index 039f0ca..c0efa69 100644
--- 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)
{
@@ -525,15 +543,131 @@ 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)
+ break;
+
+ correct = (strcmp (response, item->response) == 0);
+
+ bin_remove_item (bin, item_index);
+
+ if (correct) {
+ printf ("Correct!\n\n");
+ if (item->count < 0)
+ item->count = 1;
+ else
+ item->count++;
+ } else {
+ printf (" %s is the correct answer.\n\n",
+ item->response);
+ if (item->count > 0)
+ item->count = -1;
+ else
+ item->count--;
+ }
+
+ bin = mnemon_get_bin (mnemon, item->count);
+
+ bin_add_item (bin, item);
+ }
+}
+
int
main (int argc, char *argv[])
{
mnemon_t mnemon;
+ srand (time (NULL));
+
mnemon_init (&mnemon);
mnemon_load (&mnemon);
+ mnemon_do_challenges (&mnemon);
+
mnemon_save (&mnemon);
mnemon_fini (&mnemon);
--
2.45.2