1 files changed, 80 insertions, 0 deletions
diff --git a/appendix/useful.cxx b/appendix/useful.cxx
new file mode 100644
index 0000000..79dff57
--- /dev/null
+++ b/appendix/useful.cxx
@@ -0,0 +1,80 @@
+// FILE: useful.cxx
+// IMPLEMENTS: A toolkit of functions (See useful.h for documentation.)
+
+#include <assert.h>   // Provides assert
+#include <ctype.h>    // Provides toupper
+#include <iostream.h> // Provides cout, cin, get
+#include <stdlib.h>   // Provides rand, RAND_MAX
+#include "useful.h"
+
+void display(double x)
+// Library facilities used: iostream.h, stdlib.h
+{
+    const char STAR = '*';
+    const char BLANK = ' ';
+    const char VERTICAL_BAR = '|';
+    const int  LIMIT = 39;
+    int i;
+
+    if (x < -LIMIT)
+        x = -LIMIT;
+    else if (x > LIMIT) 
+        x = LIMIT;
+
+    for (i = -LIMIT; i < 0; i++)
+    {
+        if (i >= x)
+            cout << STAR;
+        else
+            cout << BLANK;
+    }
+    cout << VERTICAL_BAR;
+    for (i = 1; i <= LIMIT; i++)
+    {
+        if (i <= x)
+            cout << STAR;
+        else
+            cout << BLANK;
+    }
+    cout << endl;
+}
+
+double random_fraction( )
+// Library facilities used: stdlib.h
+{
+    return rand( ) / double(RAND_MAX);
+}
+
+double random_real(double low, double high)
+// Library facilities used: assert.h
+{
+    assert(low <= high);
+    return low + random_fraction( ) * (high - low);
+}
+
+void eat_line( )
+// Library facilities used: iostream.h
+// 
+{
+    char next;
+
+    do
+        cin.get(next);
+    while (next != '\n');
+}
+
+bool inquire(const char query[ ])
+// Library facilities used: ctype.h, iostream.h
+{
+    char answer;
+    do
+    {
+        cout << query << " [Yes or No]" << endl;
+        cin >> answer;
+        answer = toupper(answer);
+        eat_line( );
+    }
+    while ((answer != 'Y') && (answer != 'N'));
+    return (answer == 'Y');
+}
+