Use concrete value for quad.Quad

Comparison of -short benchmarks in cayley.

$ benchcmp pointer.bench concrete.bench
benchmark                                   old ns/op     new ns/op	delta
BenchmarkNamePredicate                      1673276       1655093	-1.09%
BenchmarkLargeSetsNoIntersection            318985907     261499984	-18.02%
BenchmarkNetAndSpeed                        104403743     41516981	-60.23%
BenchmarkKeanuAndNet                        17309258      16857513	-2.61%
BenchmarkKeanuAndSpeed                      20159161      19282833	-4.35%

Comparison of pathological cases are not so happy.

benchmark                                   old ns/op       new ns/op		delta
BenchmarkVeryLargeSetsSmallIntersection     55269775527     246084606672	+345.24%
BenchmarkHelplessContainsChecker            23436501319     24308906949		+3.72%

Profiling the worst case:

Pointer:
Total: 6121 samples
    1973  32.2%  32.2%     1973  32.2% runtime.findfunc
     773  12.6%  44.9%      773  12.6% readvarint
     510   8.3%  53.2%      511   8.3% step
     409   6.7%  59.9%      410   6.7% runtime.gentraceback
     390   6.4%  66.2%      391   6.4% pcvalue
     215   3.5%  69.8%      215   3.5% runtime.funcdata
     181   3.0%  72.7%      181   3.0% checkframecopy
     118   1.9%  74.6%      119   1.9% runtime.funcspdelta
      96   1.6%  76.2%       96   1.6% runtime.topofstack
      76   1.2%  77.5%       76   1.2% scanblock

Concrete:
Total: 25027 samples
    9437  37.7%  37.7%     9437  37.7% runtime.findfunc
    3853  15.4%  53.1%     3853  15.4% readvarint
    2366   9.5%  62.6%     2366   9.5% step
    2186   8.7%  71.3%     2186   8.7% runtime.gentraceback
    1816   7.3%  78.5%     1816   7.3% pcvalue
    1016   4.1%  82.6%     1016   4.1% runtime.funcdata
     859   3.4%  86.0%      859   3.4% checkframecopy
     506   2.0%  88.1%      506   2.0% runtime.funcspdelta
     410   1.6%  89.7%      410   1.6% runtime.topofstack
     303   1.2%  90.9%      303   1.2% runtime.newstack

http/http_test.go

@@ -25,7 +25,7 @@ import (
 var parseTests = []struct {
 	message string
 	input   string
-	expect  []*quad.Quad
+	expect  []quad.Quad
 	err     error
 }{
 	{
@@ -34,7 +34,7 @@ var parseTests = []struct {
 			{"subject": "foo", "predicate": "bar", "object": "baz"},
 			{"subject": "foo", "predicate": "bar", "object": "baz", "label": "graph"}
 		]`,
-		expect: []*quad.Quad{
+		expect: []quad.Quad{
 			{"foo", "bar", "baz", ""},
 			{"foo", "bar", "baz", "graph"},
 		},
@@ -45,7 +45,7 @@ var parseTests = []struct {
 		input: `[
 			{"subject": "foo", "predicate": "bar", "object": "foo", "something_else": "extra data"}
 		]`,
-		expect: []*quad.Quad{
+		expect: []quad.Quad{
 			{"foo", "bar", "foo", ""},
 		},
 		err: nil,
@@ -56,7 +56,7 @@ var parseTests = []struct {
 			{"subject": "foo", "predicate": "bar"}
 		]`,
 		expect: nil,
-		err:    fmt.Errorf("Invalid triple at index %d. %v", 0, &quad.Quad{"foo", "bar", "", ""}),
+		err:    fmt.Errorf("Invalid triple at index %d. %v", 0, quad.Quad{"foo", "bar", "", ""}),
 	},
 }