From 56483989cbc7c24672f4e45eaccbc537287556ce Mon Sep 17 00:00:00 2001
From: Alexander Zhirov <alexander@zhirov.website>
Date: Sun, 21 Nov 2021 15:11:59 +0300
Subject: [PATCH] example 9

---
 src/example_9/.gitignore     | 15 +++++++
 src/example_9/dub.json       |  9 +++++
 src/example_9/source/app.d   | 26 ++++++++++++
 src/example_9/source/stat_.d | 77 ++++++++++++++++++++++++++++++++++++
 4 files changed, 127 insertions(+)
 create mode 100644 src/example_9/.gitignore
 create mode 100644 src/example_9/dub.json
 create mode 100644 src/example_9/source/app.d
 create mode 100644 src/example_9/source/stat_.d

diff --git a/src/example_9/.gitignore b/src/example_9/.gitignore
new file mode 100644
index 0000000..3f2ff28
--- /dev/null
+++ b/src/example_9/.gitignore
@@ -0,0 +1,15 @@
+.dub
+docs.json
+__dummy.html
+docs/
+/example_9
+example_9.so
+example_9.dylib
+example_9.dll
+example_9.a
+example_9.lib
+example_9-test-*
+*.exe
+*.o
+*.obj
+*.lst
diff --git a/src/example_9/dub.json b/src/example_9/dub.json
new file mode 100644
index 0000000..66ac211
--- /dev/null
+++ b/src/example_9/dub.json
@@ -0,0 +1,9 @@
+{
+  "authors": [
+    "Alexander"
+  ],
+  "description": "Больше статистики. Наследование.",
+  "license": "proprietary",
+  "name": "example_9",
+  "targetPath": "bin"
+}
diff --git a/src/example_9/source/app.d b/src/example_9/source/app.d
new file mode 100644
index 0000000..8d93676
--- /dev/null
+++ b/src/example_9/source/app.d
@@ -0,0 +1,26 @@
+import std.stdio : writeln, stdin;
+import std.exception : enforce;
+import stat_;
+
+void main(string[] args)
+{
+	Stat[] stats;
+	foreach (arg; args[1 .. $])
+	{
+		auto newStat = cast(Stat) Object.factory("stat_." ~ arg);
+		enforce(newStat, "Invalid statistics function: " ~ arg);
+		stats ~= newStat;
+	}
+	for (double x; stdin.readf(" %s ", &x) == 1;)
+	{
+		foreach (s; stats)
+		{
+			s.accumulate(x);
+		}
+	}
+	foreach (s; stats)
+	{
+		s.postprocess();
+		writeln(s.result());
+	}
+}
diff --git a/src/example_9/source/stat_.d b/src/example_9/source/stat_.d
new file mode 100644
index 0000000..e13fc3b
--- /dev/null
+++ b/src/example_9/source/stat_.d
@@ -0,0 +1,77 @@
+module stat_;
+
+interface Stat
+{
+    void accumulate(double x);
+    void postprocess();
+    double result();
+}
+
+class IncrementalStat : Stat
+{
+    protected double _result;
+    abstract void accumulate(double x);
+    void postprocess()
+    {
+    }
+
+    double result()
+    {
+        return _result;
+    }
+}
+
+class Min : IncrementalStat
+{
+    this()
+    {
+        _result = double.max;
+    }
+
+    override void accumulate(double x)
+    {
+        if (x < _result)
+        {
+            _result = x;
+        }
+    }
+}
+
+class Max : IncrementalStat
+{
+    this()
+    {
+        _result = double.min_normal;
+    }
+
+    override void accumulate(double x)
+    {
+        if (x > _result)
+        {
+            _result = x;
+        }
+    }
+}
+
+class Average : IncrementalStat
+{
+    private uint items = 0;
+    this()
+    {
+        _result = 0;
+    }
+
+    override void accumulate(double x)
+    {
+        _result += x;
+        ++items;
+    }
+
+    override void postprocess()
+    {
+        if (items)
+        {
+            _result /= items;
+        }
+    }
+}