Initial Commit

go/grains/README.md

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+# Grains
+
+Write a program that calculates the number of grains of wheat on a chessboard given that the number on each square doubles.
+
+There once was a wise servant who saved the life of a prince. The king
+promised to pay whatever the servant could dream up. Knowing that the
+king loved chess, the servant told the king he would like to have grains
+of wheat. One grain on the first square of a chess board. Two grains on
+the next. Four on the third, and so on.
+
+There are 64 squares on a chessboard.
+
+Write a program that shows:
+- how many grains were on each square, and
+- the total number of grains
+
+
+## For bonus points
+
+Did you get the tests passing and the code clean? If you want to, these
+are some additional things you could try:
+
+- Optimize for speed.
+- Optimize for readability.
+
+Then please share your thoughts in a comment on the submission. Did this
+experiment make the code better? Worse? Did you learn anything from it?
+
+To run the tests simply run the command `go test` in the exercise directory.
+
+If the test suite contains benchmarks, you can run these with the `-bench`
+flag:
+
+    go test -bench .
+
+For more detailed info about the Go track see the [help
+page](http://help.exercism.io/getting-started-with-go.html).
+
+## Source
+
+JavaRanch Cattle Drive, exercise 6 [view source](http://www.javaranch.com/grains.jsp)

go/grains/grains.go

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+package grains
+
+import "errors"
+
+// Square just takes 1 * 2^sq
+func Square(sq int) (uint64, error) {
+	if sq > 0 && sq < 65 {
+		return (1 << uint(sq-1)), nil
+	}
+	return 0, errors.New("Invalid Square Requested")
+}
+
+// TotalForSquare calculates the total number
+// for all squares up to sq (cause why not)
+func TotalForSquare(sq int) (uint64, error) {
+	if sq < 0 || sq > 64 {
+		return 0, errors.New("Invalid Square Requested")
+	}
+	var ret uint64
+	for i := 0; i <= sq; i++ {
+		ret = (ret << 1) | 1
+	}
+	return ret, nil
+}
+
+// Total calculates the total for the entire board
+func Total() uint64 {
+	ret, _ := TotalForSquare(64)
+	return ret
+}

go/grains/grains_test.go

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+package grains
+
+import (
+	"testing"
+)
+
+var squareTests = []struct {
+	input       int
+	expectedVal uint64
+	expectError bool
+}{
+	{1, 1, false},
+	{2, 2, false},
+	{3, 4, false},
+	{4, 8, false},
+	{16, 32768, false},
+	{32, 2147483648, false},
+	{64, 9223372036854775808, false},
+	{65, 0, true},
+	{0, 0, true},
+	{-1, 0, true},
+}
+
+func TestSquare(t *testing.T) {
+	for _, test := range squareTests {
+		actualVal, actualErr := Square(test.input)
+		if actualVal != test.expectedVal {
+			t.Errorf("Square(%d) expected %d, Actual %d", test.input, test.expectedVal, actualVal)
+		}
+
+		// if we expect an error and there isn't one
+		if test.expectError && actualErr == nil {
+			t.Errorf("Square(%d) expected an error, but error is nil", test.input)
+		}
+		// if we don't expect an error and there is one
+		if !test.expectError && actualErr != nil {
+			t.Errorf("Square(%d) expected no error, but error is: %s", test.input, actualErr)
+		}
+	}
+}
+
+func TestTotal(t *testing.T) {
+	var expected uint64 = 18446744073709551615
+	if actual := Total(); actual != expected {
+		t.Errorf("Total() expected %d, Actual %d", expected, actual)
+	}
+}
+
+func BenchmarkSquare(b *testing.B) {
+	b.StopTimer()
+
+	for _, test := range squareTests {
+		b.StartTimer()
+
+		for i := 0; i < b.N; i++ {
+			Square(test.input)
+		}
+
+		b.StopTimer()
+	}
+}