Initial commit

README.md

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+# Triangle
+
+Write a program that can tell you if a triangle is equilateral, isosceles, or scalene.
+
+The program should raise an error if the triangle cannot exist.
+
+Tests are provided, delete one `skip` at a time.
+
+## Hint
+
+The sum of the lengths of any two sides of a triangle always exceeds the
+length of the third side, a principle known as the _triangle
+inequality_.
+
+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://exercism.io/languages/go).
+
+## Source
+
+The Ruby Koans triangle project, parts 1 & 2 [view source](http://rubykoans.com)

triangle.go

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+package triangle
+
+const testVersion = 2
+
+// Code this function.
+func KindFromSides(a, b, c float64) Kind
+
+// Notice it returns this type.  Pick something suitable.
+type Kind
+
+// Pick values for the following identifiers used by the test program.
+NaT // not a triangle
+Equ // equilateral
+Iso // isosceles
+Sca // scalene
+
+// Organize your code for readability.

triangle_test.go

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+package triangle
+
+import (
+	"math"
+	"testing"
+)
+
+const targetTestVersion = 2
+
+type testCase struct {
+	want    Kind
+	a, b, c float64
+}
+
+// basic test cases
+var testData = []testCase{
+	{Equ, 2, 2, 2},    // same length
+	{Equ, 10, 10, 10}, // a little bigger
+	{Iso, 3, 4, 4},    // last two sides equal
+	{Iso, 4, 3, 4},    // first and last sides equal
+	{Iso, 4, 4, 3},    // first two sides equal
+	{Iso, 10, 10, 2},  // again
+	{Iso, 2, 4, 2},    // a "triangle" that is just a line is still OK
+	{Sca, 3, 4, 5},    // no sides equal
+	{Sca, 10, 11, 12}, // again
+	{Sca, 5, 4, 2},    // descending order
+	{Sca, .4, .6, .3}, // small sides
+	{Sca, 1, 4, 3},    // a "triangle" that is just a line is still OK
+	{NaT, 0, 0, 0},    // zero length
+	{NaT, 3, 4, -5},   // negative length
+	{NaT, 1, 1, 3},    // fails triangle inequality
+	{NaT, 2, 5, 2},    // another
+	{NaT, 7, 3, 2},    // another
+}
+
+// generate cases with NaN and Infs, append to basic cases
+func init() {
+	nan := math.NaN()
+	pinf := math.Inf(1)
+	ninf := math.Inf(-1)
+	nf := make([]testCase, 4*4*4)
+	i := 0
+	for _, a := range []float64{3, nan, pinf, ninf} {
+		for _, b := range []float64{4, nan, pinf, ninf} {
+			for _, c := range []float64{5, nan, pinf, ninf} {
+				nf[i] = testCase{NaT, a, b, c}
+				i++
+			}
+		}
+	}
+	testData = append(testData, nf[1:]...)
+}
+
+// Test that the kinds are not equal to each other.
+// If they are equal, then TestKind will return false positives.
+func TestKindsNotEqual(t *testing.T) {
+	kindsAndNames := []struct {
+		kind Kind
+		name string
+	}{
+		{Equ, "Equ"},
+		{Iso, "Iso"},
+		{Sca, "Sca"},
+		{NaT, "NaT"},
+	}
+
+	for i, pair1 := range kindsAndNames {
+		for j := i + 1; j < len(kindsAndNames); j++ {
+			pair2 := kindsAndNames[j]
+			if pair1.kind == pair2.kind {
+				t.Fatalf("%s should not be equal to %s", pair1.name, pair2.name)
+			}
+		}
+	}
+}
+
+func TestKind(t *testing.T) {
+	for _, test := range testData {
+		got := KindFromSides(test.a, test.b, test.c)
+		if got != test.want {
+			t.Fatalf("Triangle with sides, %g, %g, %g = %v, want %v",
+				test.a, test.b, test.c, got, test.want)
+		}
+	}
+}
+
+func TestTestVersion(t *testing.T) {
+	if testVersion != targetTestVersion {
+		t.Fatalf("Found testVersion = %v, want %v", testVersion, targetTestVersion)
+	}
+}
+
+func BenchmarkKind(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, test := range testData {
+			KindFromSides(test.a, test.b, test.c)
+		}
+	}
+}