initial commit

.exercism/metadata.json

@@ -0,0 +1 @@
+{"track":"go","exercise":"leap","id":"395651d5e2594caca279b138a2b7701b","url":"https://exercism.io/my/solutions/395651d5e2594caca279b138a2b7701b","handle":"jinfield","is_requester":true,"auto_approve":false}

README.md

@@ -0,0 +1,67 @@
+# Leap
+
+Given a year, report if it is a leap year.
+
+The tricky thing here is that a leap year in the Gregorian calendar occurs:
+
+```text
+on every year that is evenly divisible by 4
+  except every year that is evenly divisible by 100
+    unless the year is also evenly divisible by 400
+```
+
+For example, 1997 is not a leap year, but 1996 is.  1900 is not a leap
+year, but 2000 is.
+
+If your language provides a method in the standard library that does
+this look-up, pretend it doesn't exist and implement it yourself.
+
+## Notes
+
+Though our exercise adopts some very simple rules, there is more to
+learn!
+
+For a delightful, four minute explanation of the whole leap year
+phenomenon, go watch [this youtube video][video].
+
+[video]: http://www.youtube.com/watch?v=xX96xng7sAE
+
+You will see a `cases_test.go` file in this exercise. This holds the test
+cases used in the `leap_test.go`. You can mostly ignore this file.
+
+However, if you are interested... we sometimes generate the test data from a
+[cross language repository][problem-specifications-leap]. In that repo
+exercises may have a [.json file][problem-specifications-leap-json] that
+contains common test data. Some of our local exercises have an
+[intermediary program][local-leap-gen] that takes the problem specification
+JSON and turns in into Go structs that are fed into the `<exercise>_test.go`
+file. The Go specific transformation of that data lives in the `cases_test.go` file.
+
+[problem-specifications-leap]: https://github.com/exercism/problem-specifications/tree/master/exercises/leap
+[problem-specifications-leap-json]: https://github.com/exercism/problem-specifications/blob/master/exercises/leap/canonical-data.json
+[local-leap-gen]: https://github.com/exercism/go/blob/master/exercises/leap/.meta/gen.go
+
+
+## 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 3 [http://www.javaranch.com/leap.jsp](http://www.javaranch.com/leap.jsp)
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.

cases_test.go

@@ -0,0 +1,17 @@
+package leap
+
+// Source: exercism/problem-specifications
+// Commit: 3134d31 leap 1.4.0: negative test: year divisible by 200, not by 400
+// Problem Specifications Version: 1.4.0
+
+var testCases = []struct {
+	year        int
+	expected    bool
+	description string
+}{
+	{2015, false, "year not divisible by 4: common year"},
+	{1996, true, "year divisible by 4, not divisible by 100: leap year"},
+	{2100, false, "year divisible by 100, not divisible by 400: common year"},
+	{2000, true, "year divisible by 400: leap year"},
+	{1800, false, "year divisible by 200, not divisible by 400: common year"},
+}

leap.go

@@ -0,0 +1,18 @@
+package leap
+
+const testVersion = 2
+
+// IsLeapYear receives an integer year value and returns a boolean indicating
+// whether the year is a leap year or not.
+func IsLeapYear(year int) bool {
+	switch {
+	case year%400 == 0:
+		return true
+	case year%100 == 0:
+		return false
+	case year%4 == 0:
+		return true
+	default:
+		return false
+	}
+}

leap_test.go

@@ -0,0 +1,22 @@
+package leap
+
+import "testing"
+
+func TestLeapYears(t *testing.T) {
+	for _, test := range testCases {
+		observed := IsLeapYear(test.year)
+		if observed != test.expected {
+			t.Fatalf("IsLeapYear(%d) = %t, want %t (%s)",
+				test.year, observed, test.expected, test.description)
+		}
+	}
+}
+
+// Benchmark 400 year interval to get fair weighting of different years.
+func Benchmark400(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for y := 1600; y < 2000; y++ {
+			IsLeapYear(y)
+		}
+	}
+}