From 9c2b4da36e944111db9f2deb00ed3404f0c56443 Mon Sep 17 00:00:00 2001
From: Timothy Warren <twarren@nabancard.com>
Date: Fri, 22 Feb 2019 11:41:57 -0500
Subject: [PATCH] Add a factorial example, checking for integer overflow

---
 .idea/misc.xml        |   1 +
 .idea/rust.iml        |   5 ++
 .idea/workspace.xml   | 166 ++++++++++++++++++++----------------------
 factorial/Cargo.toml  |   8 ++
 factorial/src/main.rs |  73 +++++++++++++++++++
 5 files changed, 167 insertions(+), 86 deletions(-)
 create mode 100644 factorial/Cargo.toml
 create mode 100644 factorial/src/main.rs

diff --git a/.idea/misc.xml b/.idea/misc.xml
index c8116fe..fc4f7d3 100644
--- a/.idea/misc.xml
+++ b/.idea/misc.xml
@@ -46,6 +46,7 @@
     <cargoProject FILE="$PROJECT_DIR$/hello/Cargo.toml" />
     <cargoProject FILE="$PROJECT_DIR$/old_lady_who_swallowed_a_fly/Cargo.toml" />
     <cargoProject FILE="$PROJECT_DIR$/fibonacci/Cargo.toml" />
+    <cargoProject FILE="$PROJECT_DIR$/factorial/Cargo.toml" />
   </component>
   <component name="ComposerJsonPluginSettings">
     <unboundedVersionInspectionSettings>
diff --git a/.idea/rust.iml b/.idea/rust.iml
index e6bb3c9..42a672f 100644
--- a/.idea/rust.iml
+++ b/.idea/rust.iml
@@ -185,6 +185,10 @@
       <sourceFolder url="file://$MODULE_DIR$/fibonacci/examples" isTestSource="false" />
       <sourceFolder url="file://$MODULE_DIR$/fibonacci/tests" isTestSource="true" />
       <sourceFolder url="file://$MODULE_DIR$/fibonacci/benches" isTestSource="true" />
+      <sourceFolder url="file://$MODULE_DIR$/factorial/src" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/factorial/examples" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/factorial/tests" isTestSource="true" />
+      <sourceFolder url="file://$MODULE_DIR$/factorial/benches" isTestSource="true" />
       <excludeFolder url="file://$MODULE_DIR$/add/add-one/target" />
       <excludeFolder url="file://$MODULE_DIR$/add/adder/target" />
       <excludeFolder url="file://$MODULE_DIR$/adder/target" />
@@ -198,6 +202,7 @@
       <excludeFolder url="file://$MODULE_DIR$/ctof/target" />
       <excludeFolder url="file://$MODULE_DIR$/enums/target" />
       <excludeFolder url="file://$MODULE_DIR$/errors/target" />
+      <excludeFolder url="file://$MODULE_DIR$/factorial/target" />
       <excludeFolder url="file://$MODULE_DIR$/fibonacci/target" />
       <excludeFolder url="file://$MODULE_DIR$/ftoc/target" />
       <excludeFolder url="file://$MODULE_DIR$/functions/target" />
diff --git a/.idea/workspace.xml b/.idea/workspace.xml
index 64ff647..a07822a 100644
--- a/.idea/workspace.xml
+++ b/.idea/workspace.xml
@@ -2,7 +2,9 @@
 <project version="4">
   <component name="ChangeListManager">
     <list default="true" id="c8f42924-1cd2-4b1c-bcff-602a3368bb16" name="Default Changelist" comment="">
-      <change beforePath="$PROJECT_DIR$/fibonacci/src/main.rs" beforeDir="false" afterPath="$PROJECT_DIR$/fibonacci/src/main.rs" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/.idea/misc.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/misc.xml" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/.idea/rust.iml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/rust.iml" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/.idea/workspace.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/workspace.xml" afterDir="false" />
     </list>
     <option name="EXCLUDED_CONVERTED_TO_IGNORED" value="true" />
     <option name="SHOW_DIALOG" value="false" />
@@ -13,19 +15,10 @@
   <component name="FileEditorManager">
     <leaf SIDE_TABS_SIZE_LIMIT_KEY="300">
       <file pinned="false" current-in-tab="false">
-        <entry file="file://$PROJECT_DIR$/old_lady_who_swallowed_a_fly/src/main.rs">
-          <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="768">
-              <caret line="48" column="10" selection-start-line="48" selection-start-column="10" selection-end-line="48" selection-end-column="10" />
-            </state>
-          </provider>
-        </entry>
-      </file>
-      <file pinned="false" current-in-tab="true">
         <entry file="file://$PROJECT_DIR$/fibonacci/src/main.rs">
           <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="496">
-              <caret line="31" column="37" selection-start-line="31" selection-start-column="37" selection-end-line="31" selection-end-column="37" />
+            <state relative-caret-position="96">
+              <caret line="6" selection-start-line="6" selection-end-line="6" />
             </state>
           </provider>
         </entry>
@@ -33,35 +26,35 @@
       <file pinned="false" current-in-tab="false">
         <entry file="file://$PROJECT_DIR$/fibonacci/Cargo.toml">
           <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="112">
-              <caret line="7" column="19" selection-start-line="7" selection-start-column="19" selection-end-line="7" selection-end-column="19" />
+            <state relative-caret-position="128">
+              <caret line="8" selection-start-line="8" selection-end-line="8" />
+            </state>
+          </provider>
+        </entry>
+      </file>
+      <file pinned="false" current-in-tab="true">
+        <entry file="file://$PROJECT_DIR$/factorial/src/main.rs">
+          <provider selected="true" editor-type-id="text-editor">
+            <state relative-caret-position="885">
+              <caret line="65" column="26" lean-forward="true" selection-start-line="65" selection-start-column="26" selection-end-line="65" selection-end-column="26" />
             </state>
           </provider>
         </entry>
       </file>
       <file pinned="false" current-in-tab="false">
-        <entry file="file://$PROJECT_DIR$/guessing_game/src/main.rs">
+        <entry file="file://$PROJECT_DIR$/old_lady_who_swallowed_a_fly/src/main.rs">
           <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="144">
-              <caret line="9" selection-start-line="9" selection-end-line="9" />
+            <state relative-caret-position="375">
+              <caret line="35" column="12" selection-start-line="35" selection-start-column="12" selection-end-line="35" selection-end-column="12" />
             </state>
           </provider>
         </entry>
       </file>
       <file pinned="false" current-in-tab="false">
-        <entry file="file://$PROJECT_DIR$/loops/src/main.rs">
+        <entry file="file://$PROJECT_DIR$/factorial/Cargo.toml">
           <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="944">
-              <caret line="59" selection-start-line="59" selection-end-line="59" />
-            </state>
-          </provider>
-        </entry>
-      </file>
-      <file pinned="false" current-in-tab="false">
-        <entry file="file://$PROJECT_DIR$/twelve_days_of_christmas/src/main.rs">
-          <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="752">
-              <caret line="47" selection-start-line="47" selection-end-line="47" />
+            <state relative-caret-position="128">
+              <caret line="8" selection-start-line="8" selection-end-line="8" />
             </state>
           </provider>
         </entry>
@@ -98,8 +91,6 @@
   <component name="IdeDocumentHistory">
     <option name="CHANGED_PATHS">
       <list>
-        <option value="$PROJECT_DIR$/closures/src/lib.rs" />
-        <option value="$PROJECT_DIR$/minigrep_v2/src/main.rs" />
         <option value="$PROJECT_DIR$/minigrep_v2/src/lib.rs" />
         <option value="$PROJECT_DIR$/add/Cargo.toml" />
         <option value="$PROJECT_DIR$/add/adder/src/main.rs" />
@@ -149,6 +140,8 @@
         <option value="$PROJECT_DIR$/old_lady_who_swallowed_a_fly/src/main.rs" />
         <option value="$PROJECT_DIR$/fibonacci/Cargo.toml" />
         <option value="$PROJECT_DIR$/fibonacci/src/main.rs" />
+        <option value="$PROJECT_DIR$/factorial/Cargo.toml" />
+        <option value="$PROJECT_DIR$/factorial/src/main.rs" />
       </list>
     </option>
   </component>
@@ -158,11 +151,11 @@
     <annotation-enable>false</annotation-enable>
     <other-services-enabled>false</other-services-enabled>
   </component>
-  <component name="ProjectFrameBounds" extendedState="6">
-    <option name="x" value="1987" />
-    <option name="y" value="-7" />
-    <option name="width" value="1080" />
-    <option name="height" value="1057" />
+  <component name="ProjectFrameBounds">
+    <option name="x" value="1680" />
+    <option name="y" value="-410" />
+    <option name="width" value="1050" />
+    <option name="height" value="1657" />
   </component>
   <component name="ProjectLevelVcsManager" settingsEditedManually="true">
     <ConfirmationsSetting value="1" id="Add" />
@@ -172,6 +165,7 @@
       <foldersAlwaysOnTop value="true" />
     </navigator>
     <panes>
+      <pane id="PackagesPane" />
       <pane id="ProjectPane">
         <subPane>
           <expand>
@@ -194,7 +188,6 @@
           <select />
         </subPane>
       </pane>
-      <pane id="PackagesPane" />
       <pane id="Scope">
         <subPane subId="Scope 'Project Files'; set:Project Files; class com.intellij.psi.search.scope.ProjectFilesScope">
           <expand>
@@ -205,13 +198,18 @@
             <path>
               <item name="rust" type="3d21c010:ScopeViewTreeModel$ProjectNode" />
               <item name="rust" type="2674bda8:ScopeViewTreeModel$GroupNode" />
-              <item name="fibonacci" type="9f88c78c:ScopeViewTreeModel$FileNode" />
+              <item name="factorial" type="9f88c78c:ScopeViewTreeModel$FileNode" />
+            </path>
+            <path>
+              <item name="rust" type="3d21c010:ScopeViewTreeModel$ProjectNode" />
+              <item name="rust" type="2674bda8:ScopeViewTreeModel$GroupNode" />
+              <item name="factorial" type="9f88c78c:ScopeViewTreeModel$FileNode" />
+              <item name="src" type="9f88c78c:ScopeViewTreeModel$FileNode" />
             </path>
             <path>
               <item name="rust" type="3d21c010:ScopeViewTreeModel$ProjectNode" />
               <item name="rust" type="2674bda8:ScopeViewTreeModel$GroupNode" />
               <item name="fibonacci" type="9f88c78c:ScopeViewTreeModel$FileNode" />
-              <item name="src" type="9f88c78c:ScopeViewTreeModel$FileNode" />
             </path>
             <path>
               <item name="rust" type="3d21c010:ScopeViewTreeModel$ProjectNode" />
@@ -254,7 +252,7 @@
   </component>
   <component name="PropertiesComponent">
     <property name="JavaScriptWeakerCompletionTypeGuess" value="true" />
-    <property name="com.android.tools.idea.instantapp.provision.ProvisionBeforeRunTaskProvider.myTimeStamp" value="1550779908787" />
+    <property name="com.android.tools.idea.instantapp.provision.ProvisionBeforeRunTaskProvider.myTimeStamp" value="1550853600931" />
     <property name="javascript.nodejs.core.library.configured.version" value="7.1.0" />
     <property name="js.eslint.eslintPackage" value="$USER_HOME$/.yarn-config/global/node_modules/.bin/eslint" />
     <property name="js.eslint.nodeInterpreter" value="project" />
@@ -288,7 +286,7 @@
       </list>
     </option>
   </component>
-  <component name="RunManager" selected="Cargo Command.Run fibonacci">
+  <component name="RunManager" selected="Cargo Command.Run factorial">
     <configuration name="&lt;template&gt;" type="TestNG" default="true" selected="false">
       <option name="MAIN_CLASS_NAME" />
       <option name="VM_PARAMETERS" value="-ea" />
@@ -307,13 +305,13 @@
         <option name="Make" enabled="true" />
       </method>
     </configuration>
-    <configuration name="Run advanced_functions" type="CargoCommandRunConfiguration" factoryName="Cargo Command" temporary="true">
+    <configuration name="Run factorial" type="CargoCommandRunConfiguration" factoryName="Cargo Command" temporary="true">
       <option name="channel" value="DEFAULT" />
-      <option name="command" value="run --package advanced_functions --bin advanced_functions" />
+      <option name="command" value="run --package factorial --bin factorial" />
       <option name="allFeatures" value="false" />
       <option name="nocapture" value="false" />
       <option name="backtrace" value="SHORT" />
-      <option name="workingDirectory" value="file://$PROJECT_DIR$/advanced_functions" />
+      <option name="workingDirectory" value="file://$PROJECT_DIR$/factorial" />
       <envs />
       <method v="2" />
     </configuration>
@@ -366,11 +364,11 @@
     </configuration>
     <recent_temporary>
       <list>
+        <item itemvalue="Cargo Command.Run factorial" />
         <item itemvalue="Cargo Command.Run fibonacci" />
         <item itemvalue="Cargo Command.Run old_lady_who_swallowed_a_fly" />
         <item itemvalue="Cargo Command.Run hello" />
         <item itemvalue="Cargo Command.Run pancakes" />
-        <item itemvalue="Cargo Command.Run advanced_functions" />
       </list>
     </recent_temporary>
   </component>
@@ -407,11 +405,11 @@
     </history-entry>
   </component>
   <component name="ToolWindowManager">
-    <frame x="1920" y="-438" width="1080" height="1897" extended-state="6" />
+    <frame x="1680" y="-410" width="1050" height="1657" extended-state="6" />
     <editor active="true" />
     <layout>
-      <window_info active="true" content_ui="combo" id="Project" order="0" sideWeight="0.49524873" visible="true" weight="0.2540132" />
-      <window_info id="Structure" order="1" sideWeight="0.50475127" side_tool="true" visible="true" weight="0.2540132" />
+      <window_info content_ui="combo" id="Project" order="0" sideWeight="0.4946058" visible="true" weight="0.26141885" />
+      <window_info id="Structure" order="1" sideWeight="0.5053942" side_tool="true" visible="true" weight="0.26141885" />
       <window_info id="Image Layers" order="2" />
       <window_info id="Designer" order="3" />
       <window_info id="Capture Tool" order="4" />
@@ -419,7 +417,7 @@
       <window_info id="Cargo" order="6" sideWeight="0.49791494" weight="0.3286119" />
       <window_info anchor="bottom" id="Message" order="0" />
       <window_info anchor="bottom" id="Find" order="1" weight="0.32979318" />
-      <window_info anchor="bottom" id="Run" order="2" weight="0.22247066" />
+      <window_info active="true" anchor="bottom" id="Run" order="2" visible="true" weight="0.22207876" />
       <window_info anchor="bottom" id="Debug" order="3" weight="0.4" />
       <window_info anchor="bottom" id="Cvs" order="4" weight="0.25" />
       <window_info anchor="bottom" id="Inspection" order="5" weight="0.4" />
@@ -427,7 +425,7 @@
       <window_info anchor="bottom" id="Docker" order="7" show_stripe_button="false" />
       <window_info anchor="bottom" id="Version Control" order="8" />
       <window_info anchor="bottom" id="Inspection Results" order="9" weight="0.32979318" />
-      <window_info anchor="bottom" id="Terminal" order="10" weight="0.34264952" />
+      <window_info anchor="bottom" id="Terminal" order="10" weight="0.34215623" />
       <window_info anchor="bottom" id="Event Log" order="11" side_tool="true" />
       <window_info anchor="right" id="Commander" order="0" weight="0.4" />
       <window_info anchor="right" id="Ant Build" order="1" weight="0.25" />
@@ -441,24 +439,6 @@
     <option name="version" value="1" />
   </component>
   <component name="editorHistoryManager">
-    <entry file="file://$PROJECT_DIR$/closures/src/main.rs">
-      <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="1120">
-          <caret line="70" column="1" selection-end-line="71" />
-        </state>
-      </provider>
-    </entry>
-    <entry file="file://$PROJECT_DIR$/closures/src/lib.rs">
-      <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="624">
-          <caret line="39" column="57" selection-start-line="39" selection-start-column="57" selection-end-line="39" selection-end-column="57" />
-          <folding>
-            <element signature="e#437#438#0" expanded="true" />
-            <element signature="e#472#473#0" expanded="true" />
-          </folding>
-        </state>
-      </provider>
-    </entry>
     <entry file="file://$PROJECT_DIR$/minigrep_v2/Cargo.toml">
       <provider selected="true" editor-type-id="text-editor">
         <state relative-caret-position="112">
@@ -819,13 +799,6 @@
         </state>
       </provider>
     </entry>
-    <entry file="file://$PROJECT_DIR$/old_lady_who_swallowed_a_fly/src/main.rs">
-      <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="768">
-          <caret line="48" column="10" selection-start-line="48" selection-start-column="10" selection-end-line="48" selection-end-column="10" />
-        </state>
-      </provider>
-    </entry>
     <entry file="file://$PROJECT_DIR$/twelve_days_of_christmas/src/main.rs">
       <provider selected="true" editor-type-id="text-editor">
         <state relative-caret-position="752">
@@ -833,13 +806,6 @@
         </state>
       </provider>
     </entry>
-    <entry file="file://$PROJECT_DIR$/guessing_game/src/main.rs">
-      <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="144">
-          <caret line="9" selection-start-line="9" selection-end-line="9" />
-        </state>
-      </provider>
-    </entry>
     <entry file="file://$PROJECT_DIR$/loops/src/main.rs">
       <provider selected="true" editor-type-id="text-editor">
         <state relative-caret-position="944">
@@ -847,17 +813,45 @@
         </state>
       </provider>
     </entry>
+    <entry file="file://$PROJECT_DIR$/guessing_game/src/main.rs">
+      <provider selected="true" editor-type-id="text-editor">
+        <state relative-caret-position="496">
+          <caret line="31" column="8" selection-start-line="31" selection-start-column="8" selection-end-line="31" selection-end-column="8" />
+        </state>
+      </provider>
+    </entry>
     <entry file="file://$PROJECT_DIR$/fibonacci/Cargo.toml">
       <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="112">
-          <caret line="7" column="19" selection-start-line="7" selection-start-column="19" selection-end-line="7" selection-end-column="19" />
+        <state relative-caret-position="128">
+          <caret line="8" selection-start-line="8" selection-end-line="8" />
+        </state>
+      </provider>
+    </entry>
+    <entry file="file://$PROJECT_DIR$/factorial/Cargo.toml">
+      <provider selected="true" editor-type-id="text-editor">
+        <state relative-caret-position="128">
+          <caret line="8" selection-start-line="8" selection-end-line="8" />
+        </state>
+      </provider>
+    </entry>
+    <entry file="file://$PROJECT_DIR$/old_lady_who_swallowed_a_fly/src/main.rs">
+      <provider selected="true" editor-type-id="text-editor">
+        <state relative-caret-position="375">
+          <caret line="35" column="12" selection-start-line="35" selection-start-column="12" selection-end-line="35" selection-end-column="12" />
         </state>
       </provider>
     </entry>
     <entry file="file://$PROJECT_DIR$/fibonacci/src/main.rs">
       <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="496">
-          <caret line="31" column="37" selection-start-line="31" selection-start-column="37" selection-end-line="31" selection-end-column="37" />
+        <state relative-caret-position="96">
+          <caret line="6" selection-start-line="6" selection-end-line="6" />
+        </state>
+      </provider>
+    </entry>
+    <entry file="file://$PROJECT_DIR$/factorial/src/main.rs">
+      <provider selected="true" editor-type-id="text-editor">
+        <state relative-caret-position="885">
+          <caret line="65" column="26" lean-forward="true" selection-start-line="65" selection-start-column="26" selection-end-line="65" selection-end-column="26" />
         </state>
       </provider>
     </entry>
diff --git a/factorial/Cargo.toml b/factorial/Cargo.toml
new file mode 100644
index 0000000..bc4c207
--- /dev/null
+++ b/factorial/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "factorial"
+version = "0.1.0"
+authors = ["Timothy Warren <twarren@nabancard.com>"]
+edition = "2018"
+
+[dependencies]
+separator = "0.4.0"
diff --git a/factorial/src/main.rs b/factorial/src/main.rs
new file mode 100644
index 0000000..9fc80b3
--- /dev/null
+++ b/factorial/src/main.rs
@@ -0,0 +1,73 @@
+extern crate separator;
+
+use separator::Separatable;
+
+use std::io;
+use std::u128;
+
+///! Calculate a number in the fibonnacci sequence,
+///! using a lookup table for better worst-case performance.
+///
+/// Can calculate up to 34! using native unsigned 128 bit integers.
+/// If the result overflows, an error message will be displayed.
+fn factorial (n: usize, table: &mut Vec<u128>) -> Option<u128> {
+    match table.get(n) {
+        Some(x) => {
+            // Vec<T>.get returns a Option with a reference to the value, so deref
+            // Wrap in Some() for proper return type
+            Some(*x)
+        },
+        None => {
+            // If a previous base overflowed, just
+            // pass on the overflow. The overflow will
+            // be caught later. Using the max value of u128
+            // for convenience.
+            let prev = factorial(n - 1, table)
+                .unwrap_or(u128::MAX);
+
+            // Do an overflow-checked multiply
+            let attempt = (n as u128).checked_mul(prev);
+
+            // If there isn't an overflow, add the result
+            // to the calculation table
+            if let Some(current) = attempt {
+                table.insert(n, current);
+            }
+
+            attempt // Some(x) if no overflow
+        }
+    }
+}
+
+fn main() {
+    // The lookup table for previously calculated values
+    let mut table: Vec<u128> = vec![1, 1, 2];
+
+    println!("Factorial calculator.");
+    println!("Any non-number will exit.");
+
+    loop {
+        println!("\nWhich factorial to calculate?");
+
+        let mut index = String::new();
+
+        io::stdin().read_line(&mut index)
+            .expect("Failed to read line");
+
+        let index = match index.trim().parse() {
+            Ok(num) => num,
+            Err(_) => break, // Exit on non-number
+        };
+
+        println!("Calculating factorial of: {}", index);
+
+        match factorial(index, &mut table) {
+            Some(calculated) => {
+                println!("{}! is {}", index, calculated.separated_string())
+            },
+            None => {
+                println!("Calculation overflow. The factorial base was too large.");
+            }
+        }
+    }
+}