Add new example based on set and word counts.

example/ex-dict04.c

@@ -0,0 +1,18 @@
+#include <stdio.h>
+#include "m-string.h"
+#include "m-dict.h"
+
+/* program that reads text from standard-input, 
+   and prints the total number of distinct words found in the text. 
+*/
+DICT_SET_DEF2(str, string_t, STRING_OPLIST)
+
+int main(void)
+{
+  M_LET(word, STRING_OPLIST)
+    M_LET(wordcount, DICT_SET_OPLIST(str, STRING_OPLIST)) {
+    while (string_fget_word(word, " \t\n,.!;:?", stdin))
+      dict_str_set_at(wordcount, word);
+    printf ("Words: %lu\n", dict_str_size(wordcount));
+  }
+}