Add grains exercise

go/grains/.exercism/metadata.json

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+{"track":"go","exercise":"grains","id":"d8647ac08b804c3694df91f5de19e23c","url":"https://exercism.io/my/solutions/d8647ac08b804c3694df91f5de19e23c","handle":"lurraca","is_requester":true,"auto_approve":false}

go/grains/README.md

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+# Grains
+
+Calculate 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 code 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?
+
+## Running the tests
+
+To run the tests run the command `go test` from within the exercise directory.
+
+If the test suite contains benchmarks, you can run these with the `--bench` and `--benchmem`
+flags:
+
+    go test -v --bench . --benchmem
+
+Keep in mind that each reviewer will run benchmarks on a different machine, with
+different specs, so the results from these benchmark tests may vary.
+
+## Further information
+
+For more detailed information about the Go track, including how to get help if
+you're having trouble, please visit the exercism.io [Go language page](http://exercism.io/languages/go/resources).
+
+## Source
+
+JavaRanch Cattle Drive, exercise 6 [http://www.javaranch.com/grains.jsp](http://www.javaranch.com/grains.jsp)
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.

go/grains/cases_test.go

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+package grains
+
+// Source: exercism/problem-specifications
+// Commit: f079c2d grains: Move input (square) to input object (#1191)
+// Problem Specifications Version: 1.1.0
+
+// returns the number of grains on the square
+var squareTests = []struct {
+	description string
+	input       int
+	expectedVal uint64
+	expectError bool
+}{
+	{
+		description: "1",
+		input:       1,
+		expectedVal: 1,
+	},
+	{
+		description: "2",
+		input:       2,
+		expectedVal: 2,
+	},
+	{
+		description: "3",
+		input:       3,
+		expectedVal: 4,
+	},
+	{
+		description: "4",
+		input:       4,
+		expectedVal: 8,
+	},
+	{
+		description: "16",
+		input:       16,
+		expectedVal: 32768,
+	},
+	{
+		description: "32",
+		input:       32,
+		expectedVal: 2147483648,
+	},
+	{
+		description: "64",
+		input:       64,
+		expectedVal: 9223372036854775808,
+	},
+	{
+		description: "square 0 returns an error",
+		input:       0,
+		expectError: true,
+	},
+	{
+		description: "negative square returns an error",
+		input:       -1,
+		expectError: true,
+	},
+	{
+		description: "square greater than 64 returns an error",
+		input:       65,
+		expectError: true,
+	},
+}

go/grains/grains.go

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+package grains
+
+func Square(n int) (uint64, error) { 
+	return 0, nil
+}
+
+func Total() uint64 {
+	return 0
+}

go/grains/grains_test.go

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+package grains
+
+import (
+	"testing"
+)
+
+func TestSquare(t *testing.T) {
+	for _, test := range squareTests {
+		actualVal, actualErr := Square(test.input)
+
+		// check actualVal only if no error expected
+		if !test.expectError && actualVal != test.expectedVal {
+			t.Fatalf("FAIL: %s\nSquare(%d) expected %d, Actual %d", test.description, test.input, test.expectedVal, actualVal)
+		}
+
+		// if we expect an error and there isn't one
+		if test.expectError && actualErr == nil {
+			t.Fatalf("FAIL: %s\nSquare(%d) expected an error, but error is nil", test.description, test.input)
+		}
+		// if we don't expect an error and there is one
+		if !test.expectError && actualErr != nil {
+			var _ error = actualErr
+			t.Fatalf("FAIL: %s\nSquare(%d) expected no error, but error is: %s", test.description, test.input, actualErr)
+		}
+		t.Logf("PASS: %s", test.description)
+	}
+}
+
+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) {
+
+	for i := 0; i < b.N; i++ {
+
+		for _, test := range squareTests {
+			Square(test.input)
+		}
+
+	}
+}
+
+func BenchmarkTotal(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		Total()
+	}
+}