From 68bcbf1e0e61958f737bfc279974903f1b0c2502 Mon Sep 17 00:00:00 2001
From: tomsmeding <tom.smeding@gmail.com>
Date: Sat, 15 Oct 2016 09:32:53 +0200
Subject: Initial

---
 .gitignore |  3 +++
 Makefile   | 24 ++++++++++++++++++++++++
 stddev.cpp | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 74 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Makefile
 create mode 100644 stddev.cpp

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..1b6649e
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+stddev
+*.o
+*.dSYM
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..733d520
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,24 @@
+CXX = g++
+CXXFLAGS = -Wall -Wextra -std=c++11 -fwrapv
+ifneq ($(DEBUG),)
+	CXXFLAGS += -g
+else
+	CXXFLAGS += -O2
+endif
+BIN = stddev
+
+.PHONY: all clean remake
+
+all: $(BIN)
+
+clean:
+	rm -rf $(BIN) *.o *.dSYM
+
+remake: clean all
+
+
+$(BIN): $(patsubst %.cpp,%.o,$(wildcard *.cpp))
+	$(CXX) -o $@ $^
+
+%.o: %.cpp $(wildcard *.h)
+	$(CXX) $(CXXFLAGS) -c -o $@ $<
diff --git a/stddev.cpp b/stddev.cpp
new file mode 100644
index 0000000..c804bf3
--- /dev/null
+++ b/stddev.cpp
@@ -0,0 +1,47 @@
+#include <iostream>
+#include <vector>
+#include <cmath>
+
+using namespace std;
+
+const char *argv0;
+
+void usage(){
+	cerr<<"Usage: "<<argv0<<endl
+	    <<"Prints some statistical information about the data on stdin."<<endl
+	    <<"Data is assumed to be a list of floating-point values."<<endl;
+}
+
+int main(int,char **argv){
+	argv0=argv[0];
+
+	vector<double> data;
+
+	double total=0;
+	while(true){
+		double v;
+		cin>>v;
+		if(!cin)break;
+		data.push_back(v);
+		total+=v;
+	}
+	if(data.size()==0){
+		cerr<<"No data"<<endl;
+		return 0;
+	}
+
+	sort(data.begin(),data.end());
+
+	const double s_mean=total/data.size();
+	const double s_mode=data[data.size()/2];
+
+	total=0;
+	for(double v : data){
+		total+=(v-s_mean)*(v-s_mean);
+	}
+	const double s_stddev=data.size()==1?nan(""):sqrt(total/(data.size()-1));
+
+	cout<<"Mean:   "<<s_mean<<endl
+	    <<"Stddev: "<<s_stddev<<endl
+	    <<"Mode:   "<<s_mode<<endl;
+}
-- 
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