1 files changed, 73 insertions, 0 deletions
diff --git a/tpl/compare/truth.go b/tpl/compare/truth.go
new file mode 100644
index 000000000..85ee22121
--- /dev/null
+++ b/tpl/compare/truth.go
@@ -0,0 +1,73 @@
+// Copyright 2019 The Hugo Authors. All rights reserved.
+// The functions in this file is based on the Go source code, copyright
+// The Go Authors and  governed by a BSD-style license.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package compare provides template functions for comparing values.
+package compare
+
+import (
+	"reflect"
+
+	"github.com/gohugoio/hugo/common/hreflect"
+)
+
+// Boolean logic, based on:
+// https://github.com/golang/go/blob/178a2c42254166cffed1b25fb1d3c7a5727cada6/src/text/template/funcs.go#L302
+
+func truth(arg reflect.Value) bool {
+	return hreflect.IsTruthfulValue(arg)
+}
+
+// getIf will return the given arg if it is considered truthful, else an empty string.
+func (*Namespace) getIf(arg reflect.Value) reflect.Value {
+	if truth(arg) {
+		return arg
+	}
+	return reflect.ValueOf("")
+}
+
+// And computes the Boolean AND of its arguments, returning
+// the first false argument it encounters, or the last argument.
+func (*Namespace) And(arg0 reflect.Value, args ...reflect.Value) reflect.Value {
+	if !truth(arg0) {
+		return arg0
+	}
+	for i := range args {
+		arg0 = args[i]
+		if !truth(arg0) {
+			break
+		}
+	}
+	return arg0
+}
+
+// Or computes the Boolean OR of its arguments, returning
+// the first true argument it encounters, or the last argument.
+func (*Namespace) Or(arg0 reflect.Value, args ...reflect.Value) reflect.Value {
+	if truth(arg0) {
+		return arg0
+	}
+	for i := range args {
+		arg0 = args[i]
+		if truth(arg0) {
+			break
+		}
+	}
+	return arg0
+}
+
+// Not returns the Boolean negation of its argument.
+func (*Namespace) Not(arg reflect.Value) bool {
+	return !truth(arg)
+}