From c1b6ffe70bd281c6c230fd63fabcaac2aff47514 Mon Sep 17 00:00:00 2001
From: Fuwn <contact@fuwn.me>
Date: Sun, 7 Apr 2024 23:18:32 -0700
Subject: feat: initial commit

---
 appendix/useful.cxx | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 appendix/useful.h   | 45 ++++++++++++++++++++++++++++++
 2 files changed, 125 insertions(+)
 create mode 100644 appendix/useful.cxx
 create mode 100644 appendix/useful.h

(limited to 'appendix')

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');
+}
+
diff --git a/appendix/useful.h b/appendix/useful.h
new file mode 100644
index 0000000..4513936
--- /dev/null
+++ b/appendix/useful.h
@@ -0,0 +1,45 @@
+// FILE: useful.h
+// PROVIDES: A toolkit of useful functions for random numbers and displays.
+//
+// FUNCTIONS in the toolkit:
+//   double random_fraction( )
+//     Postcondition: The return value is a random real number in the closed
+//     interval [0..1] (including the endpoints).
+//
+//   double random_real(double low, double high)
+//     Precondition: low <= high.
+//     Postcondition: The return value is a random real number in the closed
+//     interval [low..high] (including the endpoints).
+//
+//   void display(double x)
+//     Postcondition: The function has written one line of output to the
+//     standard ouput, with a vertical bar in the middle. If x is positive,
+//     then approximately x stars are printed to the right of the vertical
+//     bar. If x is negative, then approximately -x stars are printed to the
+//     left of the vertical bar. If the absolute value of x is more than
+//     39, then only 39 stars are printed.
+//     Examples:
+//     display(8) prints:                          |********
+//     display(-4) prints:                     ****|
+//
+//   void eat_line( )
+//     Postcondition: Up to next newline has been read and discarded from cin.
+//
+//   bool inquire(const char query[ ])
+//     Precondition: query is a null-terminated string of characters.
+//     Postcondition: query has been printed, and a one-line response read 
+//     from the user. The function returns true if the user's response begins 
+//     with 'Y' or 'y', and returns false if the user's response begins with 
+//     'N' or 'n'. (If the response begins with some other letter, then the
+//     query is repeated.)
+
+#ifndef USEFUL_H  // Prevent duplicate definition
+#define USEFUL_H
+
+    double random_fraction( );
+    double random_real(double low, double high);
+    void display(double x);
+    void eat_line( );
+    bool inquire(const char query[ ]);
+
+#endif
-- 
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