Correct way of adding exercise

Author: frank-at-adacore

courses/comprehensive_rust_training/110_std_types.rst

@@ -43,4 +43,4 @@ Std Types
 .. include:: 110_std_types/05_string.rst
 .. include:: 110_std_types/06_vec.rst
 .. include:: 110_std_types/07_hashmap.rst
-.. include:: 110_std_types/08_exercise.rst
+.. include:: 110_std_types/99_lab.rst

courses/comprehensive_rust_training/110_std_types/08_exercise.rst courses/comprehensive_rust_training/110_std_types/99_lab.rst

@@ -3,7 +3,7 @@ Exercise: Counter
 ===================
 
 -------------------
-Exercise: Counter
+Counter Problem
 -------------------
 
 In this exercise you will take a very simple data structure and make it
@@ -53,4 +53,15 @@ method to halve the number of hash lookups required to implement the
        }
    }
 
-   {{#include exercise.rs:main}}
+------------------------
+Counter - Main Program
+------------------------
+
+.. container:: source_include 110_std_types/src/110_std_types.rs :start-after://ANCHOR-main :code:rust :number-lines:1
+
+-------------------
+Counter Solution
+-------------------
+
+.. container:: source_include 110_std_types/src/110_std_types.rs :start-after://ANCHOR-solution :end-before://ANCHOR-main :code:rust :number-lines:1
+

courses/comprehensive_rust_training/110_std_types/src/110_std_types.rs

@@ -0,0 +1,61 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#![allow(unused_variables, dead_code)]
+//ANCHOR-solution
+use std::collections::HashMap;
+use std::hash::Hash;
+
+/// Counter counts the number of times each value of type T has been seen.
+struct Counter<T> {
+    values: HashMap<T, u64>,
+}
+
+impl<T: Eq + Hash> Counter<T> {
+    /// Create a new Counter.
+    fn new() -> Self {
+        Counter { values: HashMap::new() }
+    }
+
+    /// Count an occurrence of the given value.
+    fn count(&mut self, value: T) {
+        *self.values.entry(value).or_default() += 1;
+    }
+
+    /// Return the number of times the given value has been seen.
+    fn times_seen(&self, value: T) -> u64 {
+        self.values.get(&value).copied().unwrap_or_default()
+    }
+}
+
+//ANCHOR-main
+fn main() {
+    let mut ctr = Counter::new();
+    ctr.count(13);
+    ctr.count(14);
+    ctr.count(16);
+    ctr.count(14);
+    ctr.count(14);
+    ctr.count(11);
+
+    for i in 10..20 {
+        println!("saw {} values equal to {}", ctr.times_seen(i), i);
+    }
+
+    let mut strctr = Counter::new();
+    strctr.count("apple");
+    strctr.count("orange");
+    strctr.count("apple");
+    println!("got {} apples", strctr.times_seen("apple"));
+}