Implementing "Average" example

and supporting `Stdin.ReadDouble` method.

algs4/src/go/Makefile

@@ -5,7 +5,8 @@ TARGETS := \
 	$(REPO_BASE)/algs4-flips \
 	$(REPO_BASE)/algs4-gcd \
 	$(REPO_BASE)/algs4-rolls \
-	$(REPO_BASE)/algs4-randomseq
+	$(REPO_BASE)/algs4-randomseq \
+	$(REPO_BASE)/algs4-average
 
 test: build
 	go test -x $(TARGETS)

algs4/src/go/algs4-average/main.go

@@ -0,0 +1,37 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"os"
+)
+
+import (
+	"github.com/meatballhat/box-o-sand/algs4/src/go/algs4"
+)
+
+func die(err error) {
+	fmt.Fprintf(os.Stderr, "ERROR: %v\n", err)
+	os.Exit(1)
+}
+
+func main() {
+	sum := 0.0
+	cnt := 0
+
+	for {
+		d, err := algs4.Stdin.ReadDouble()
+		if err == io.EOF {
+			break
+		}
+
+		if err != nil {
+			die(err)
+		}
+
+		sum += d
+		cnt++
+	}
+
+	fmt.Printf("Average is %.5f\n", sum/float64(cnt))
+}

algs4/src/go/algs4/io.go

@@ -3,10 +3,38 @@ package algs4
 import (
 	"bufio"
 	"io"
+	"os"
 	"strconv"
 	"strings"
 )
 
+type inputWrapper struct {
+	Inbuf *bufio.Reader
+}
+
+var (
+	Stdin = &inputWrapper{}
+)
+
+func init() {
+	Stdin.Inbuf = bufio.NewReader(os.Stdin)
+}
+
+func (in *inputWrapper) ReadDouble() (float64, error) {
+	line, err := in.Inbuf.ReadString('\n')
+
+	if err != nil {
+		return float64(0), err
+	}
+
+	dbl, err := strconv.ParseFloat(strings.TrimSpace(line), 64)
+	if err != nil {
+		return float64(0), err
+	}
+
+	return dbl, nil
+}
+
 func ReadInts(inbuf io.Reader) ([]int, error) {
 	ints := make([]int, 0)