Add set, unset, and hasKey.

README.md

@@ -166,6 +166,13 @@ parse, it returns the time unaltered. See `time.ParseDuration` for info on durat
   follows: []byte are converted, fmt.Stringers will have String() called.
   errors will have Error() called. All others will be passed through
   fmt.Sprtinf("%v").
+- set: Takes a dict, a key, and a value, and sets that key/value pair in
+  the dict. `set $dict $key $value`. For convenience, it returns the dict,
+  even though the dict was modified in place.
+- unset: Takes a dict and a key, and deletes that key/value pair from the
+  dict. `unset $dict $key`. This returns the dict for convenience.
+- hasKey: Takes a dict and a key, and returns boolean true if the key is in
+  the dict.
 
 ```
 {{$t := tuple 1 "a" "foo"}}

functions.go

@@ -143,6 +143,13 @@ Data Structures:
 	  follows: []byte are converted, fmt.Stringers will have String() called.
 	  errors will have Error() called. All others will be passed through
 	  fmt.Sprtinf("%v").
+	- set: Takes a dict, a key, and a value, and sets that key/value pair in
+	  the dict. `set $dict $key $value`. For convenience, it returns the dict,
+	  even though the dict was modified in place.
+	- unset: Takes a dict and a key, and deletes that key/value pair from the
+	  dict. `unset $dict $key`. This returns the dict for convenience.
+	- hasKey: Takes a dict and a key, and returns boolean true if the key is in
+	  the dict.
 
 Math Functions:
 
@@ -386,8 +393,11 @@ var genericMap = map[string]interface{}{
 	"b32dec": base32decode,
 
 	// Data Structures:
-	"tuple": tuple,
-	"dict":  dict,
+	"tuple":  tuple,
+	"dict":   dict,
+	"set":    set,
+	"unset":  unset,
+	"hasKey": hasKey,
 
 	// Crypto:
 	"genPrivateKey": generatePrivateKey,
@@ -650,6 +660,21 @@ func tuple(v ...interface{}) []interface{} {
 	return v
 }
 
+func set(d map[string]interface{}, key string, value interface{}) map[string]interface{} {
+	d[key] = value
+	return d
+}
+
+func unset(d map[string]interface{}, key string) map[string]interface{} {
+	delete(d, key)
+	return d
+}
+
+func hasKey(d map[string]interface{}, key string) bool {
+	_, ok := d[key]
+	return ok
+}
+
 func dict(v ...interface{}) map[string]interface{} {
 	dict := map[string]interface{}{}
 	lenv := len(v)

functions_test.go

@@ -285,6 +285,16 @@ func TestEmpty(t *testing.T) {
 	if err := runt(tpl, "1"); err != nil {
 		t.Error(err)
 	}
+
+	dict := map[string]interface{}{"top": map[string]interface{}{}}
+	tpl = `{{if empty .top.NoSuchThing}}1{{else}}0{{end}}`
+	if err := runtv(tpl, "1", dict); err != nil {
+		t.Error(err)
+	}
+	tpl = `{{if empty .bottom.NoSuchThing}}1{{else}}0{{end}}`
+	if err := runtv(tpl, "1", dict); err != nil {
+		t.Error(err)
+	}
 }
 
 func TestSplit(t *testing.T) {
@@ -523,6 +533,43 @@ func TestDict(t *testing.T) {
 	}
 }
 
+func TestUnset(t *testing.T) {
+	tpl := `{{- $d := dict "one" 1 "two" 222222 -}}
+	{{- $_ := unset $d "two" -}}
+	{{- range $k, $v := $d}}{{$k}}{{$v}}{{- end -}}
+	`
+
+	expect := "one1"
+	if err := runt(tpl, expect); err != nil {
+		t.Error(err)
+	}
+}
+func TestHasKey(t *testing.T) {
+	tpl := `{{- $d := dict "one" 1 "two" 222222 -}}
+	{{- if hasKey $d "one" -}}1{{- end -}}
+	`
+
+	expect := "1"
+	if err := runt(tpl, expect); err != nil {
+		t.Error(err)
+	}
+}
+
+func TestSet(t *testing.T) {
+	tpl := `{{- $d := dict "one" 1 "two" 222222 -}}
+	{{- $_ := set $d "two" 2 -}}
+	{{- $_ := set $d "three" 3 -}}
+	{{- if hasKey $d "one" -}}{{$d.one}}{{- end -}}
+	{{- if hasKey $d "two" -}}{{$d.two}}{{- end -}}
+	{{- if hasKey $d "three" -}}{{$d.three}}{{- end -}}
+	`
+
+	expect := "123"
+	if err := runt(tpl, expect); err != nil {
+		t.Error(err)
+	}
+}
+
 func TestUntil(t *testing.T) {
 	tests := map[string]string{
 		`{{range $i, $e := until 5}}{{$i}}{{$e}}{{end}}`:   "0011223344",