exp/template: add a tree-walking example to the test.
Also fix a comment formatting glitch.
R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/4672054
diff --git a/src/pkg/exp/template/exec.go b/src/pkg/exp/template/exec.go
index 09bf858..42279c2 100644
--- a/src/pkg/exp/template/exec.go
+++ b/src/pkg/exp/template/exec.go
@@ -267,7 +267,7 @@
// The 'final' argument represents the return value from the preceding
// value of the pipeline, if any.
// If we're in a chain, such as (.X.Y.Z), .X and .Y cannot be methods;
-//canBeMethod will be true only for the last element of such chains (here .Z).
+// canBeMethod will be true only for the last element of such chains (here .Z).
// The isFirst argument tells whether this is the first element of a chain (here .X).
// If true, evaluation is allowed to examine the parent to resolve the reference.
func (s *state) evalField(data reflect.Value, fieldName string, args []node, final reflect.Value,
diff --git a/src/pkg/exp/template/exec_test.go b/src/pkg/exp/template/exec_test.go
index db3e89f..5d771a2 100644
--- a/src/pkg/exp/template/exec_test.go
+++ b/src/pkg/exp/template/exec_test.go
@@ -346,3 +346,84 @@
}
}
}
+
+// A nice example: walk a binary tree.
+
+type Tree struct {
+ Val int
+ Left, Right *Tree
+}
+
+const treeTemplate = `
+ {{define "tree"}}
+ [
+ {{.Val}}
+ {{with .Left}}
+ {{template "tree" .}}
+ {{end}}
+ {{with .Right}}
+ {{template "tree" .}}
+ {{end}}
+ ]
+ {{end}}
+`
+
+func TestTree(t *testing.T) {
+ var tree = &Tree{
+ 1,
+ &Tree{
+ 2, &Tree{
+ 3,
+ &Tree{
+ 4, nil, nil,
+ },
+ nil,
+ },
+ &Tree{
+ 5,
+ &Tree{
+ 6, nil, nil,
+ },
+ nil,
+ },
+ },
+ &Tree{
+ 7,
+ &Tree{
+ 8,
+ &Tree{
+ 9, nil, nil,
+ },
+ nil,
+ },
+ &Tree{
+ 10,
+ &Tree{
+ 11, nil, nil,
+ },
+ nil,
+ },
+ },
+ }
+ set := NewSet()
+ err := set.Parse(treeTemplate)
+ if err != nil {
+ t.Fatal("parse error:", err)
+ }
+ var b bytes.Buffer
+ err = set.Execute("tree", &b, tree)
+ if err != nil {
+ t.Fatal("exec error:", err)
+ }
+ stripSpace := func(r int) int {
+ if r == '\t' || r == '\n' {
+ return -1
+ }
+ return r
+ }
+ result := strings.Map(stripSpace, b.String())
+ const expect = "[1[2[3[4]][5[6]]][7[8[9]][10[11]]]]"
+ if result != expect {
+ t.Errorf("expected %q got %q", expect, result)
+ }
+}
