sieve: add generator

Add .meta/gen.go to generate cases_test.go.

Update test program to use generated test case array.

Update example solution to pass test which includes limit as prime.

For exercism#605.

exercises/sieve/.meta/gen.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"log"
+	"text/template"
+
+	"../../../gen"
+)
+
+func main() {
+	t, err := template.New("").Parse(tmpl)
+	if err != nil {
+		log.Fatal(err)
+	}
+	var j js
+	if err := gen.Gen("sieve", &j, t); err != nil {
+		log.Fatal(err)
+	}
+}
+
+type OneCase struct {
+	Description string
+	Limit       int
+	Expected    []int
+}
+
+// The JSON structure we expect to be able to unmarshal into
+type js struct {
+	Cases []OneCase
+}
+
+// template applied to above data structure generates the Go test cases
+var tmpl = `package sieve
+
+{{.Header}}
+
+var testCases = []struct {
+	description string
+	limit int
+	expected []int
+}{
+{{range .J.Cases}}{
+	"{{.Description}}",
+	{{.Limit}},
+	{{printf "%#v" .Expected}},
+},
+{{end}}}
+`

exercises/sieve/cases_test.go

@@ -0,0 +1,37 @@
+package sieve
+
+// Source: exercism/problem-specifications
+// Commit: f2b2693 sieve: Fix canonical-data.json formatting
+// Problem Specifications Version: 1.0.0
+
+var testCases = []struct {
+	description string
+	limit       int
+	expected    []int
+}{
+	{
+		"no primes under two",
+		1,
+		[]int{},
+	},
+	{
+		"find first prime",
+		2,
+		[]int{2},
+	},
+	{
+		"find primes up to 10",
+		10,
+		[]int{2, 3, 5, 7},
+	},
+	{
+		"limit is prime",
+		13,
+		[]int{2, 3, 5, 7, 11, 13},
+	},
+	{
+		"find primes up to 1000",
+		1000,
+		[]int{2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997},
+	},
+}

exercises/sieve/example.go

@@ -1,15 +1,15 @@
 package sieve
 
 func Sieve(limit int) (primes []int) {
-	c := make([]bool, limit)
-	for p := 2; p < limit; {
-		for i := p + p; i < limit; i += p {
+	c := make([]bool, limit+1)
+	for p := 2; p <= limit; {
+		for i := p + p; i <= limit; i += p {
 			c[i] = true
 		}
-		for p++; p < limit && c[p]; p++ {
+		for p++; p <= limit && c[p]; p++ {
 		}
 	}
-	for i := 2; i < limit; i++ {
+	for i := 2; i <= limit; i++ {
 		if !c[i] {
 			primes = append(primes, i)
 		}

exercises/sieve/sieve_test.go

@@ -5,32 +5,23 @@ import (
 	"testing"
 )
 
-var p10 = []int{2, 3, 5, 7}
-var p1000 = []int{2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53,
-	59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137,
-	139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223,
-	227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307,
-	311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397,
-	401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487,
-	491, 499, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593,
-	599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677,
-	683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787,
-	797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883,
-	887, 907, 911, 919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997}
-
 func TestSieve(t *testing.T) {
-	p := Sieve(10)
-	if !reflect.DeepEqual(p, p10) {
-		t.Fatalf("Sieve(10) = %v, want %v", p, p10)
-	}
-	p = Sieve(1000)
-	if !reflect.DeepEqual(p, p1000) {
-		t.Fatalf("Sieve(1000) = %v, want %v", p, p1000)
+	for _, tc := range testCases {
+		p := Sieve(tc.limit)
+		if len(p) != 0 || len(tc.expected) != 0 {
+			if !reflect.DeepEqual(p, tc.expected) {
+				t.Fatalf("FAIL: %s\nSieve(%d)\nExpected %v\nActual  %v",
+					tc.description, tc.limit, tc.expected, p)
+			}
+		}
+		t.Logf("PASS: %s", tc.description)
 	}
 }
 
 func BenchmarkSieve(b *testing.B) {
 	for i := 0; i < b.N; i++ {
-		Sieve(1000)
+		for _, tc := range testCases {
+			Sieve(tc.limit)
+		}
 	}
 }