better test for encoding values with quotes

README.md

@@ -83,19 +83,19 @@ Multiple top-level forms are allowed and returned as an array of Nodes by the de
 Writes the Node object in brief format.
 
 ```go
-var Node Node
+var node Node
 var out io.Writer
-err := Node.Encode(out)
+err := node.Encode(out)
 ```
 
 ### Brief XML Output
 
 Writes the Node object in XML format.
 
 ```go
-var Node Node
+var node Node
 var out io.Writer
-err := Node.WriteXML(out)
+err := node.WriteXML(out)
 ```
 
 XML output uses a template.  This serves as an example of using brief with a template.
@@ -179,15 +179,15 @@ Lookup is a Node method which gets a context value from a value spec.
 Slice is a Node method which creates a slice of strings from a sequence of value specs.
 
 ```text/template
-{{ print .Slice "project.id" "project" }}
+{{ .Slice "project.id" "project" }}
 ```
 
 #### Join
 
 Join is a Node method which combines sequence of strings using a separator from a sequence of value specs.
 
 ```text/template
-{{ print .Join "/" "project.id" "project" }}
+{{ .Join "/" "project.id" "project" }}
 ```
 
 #### Printf

encoder.go

@@ -3,7 +3,7 @@ package brief
 import (
 	"fmt"
 	"strings"
-	"unicode"
+	"text/scanner"
 )
 
 // Encode converts a node into brief format
@@ -20,17 +20,33 @@ func (node *Node) Encode() []byte {
 	return []byte(out.String())
 }
 
-func isIdentRune(ch rune, i int) bool {
-	return ch == '_' || unicode.IsLetter(ch) || unicode.IsDigit(ch) && i > 0
-}
-
-func isSymbol(token string) bool {
-	for i, ch := range token {
-		if !isIdentRune(ch, i) {
+// NoQuote tests if the value is an identifier or number
+func NoQuote(value string) bool {
+	var s scanner.Scanner
+	s.Init(strings.NewReader(value))
+	tok := s.Scan()
+	var minus bool
+	for {
+		switch tok {
+		case scanner.Ident:
+			return !minus && s.TokenText() == value
+		case scanner.Float, scanner.Int:
+			numval := s.TokenText()
+			if minus {
+				numval = "-" + numval
+			}
+			return numval == value
+		case '-':
+			if minus {
+				return false
+			}
+			minus = true
+			tok = s.Scan()
+		default:
 			return false
 		}
 	}
-	return true
+
 }
 
 func (node *Node) write(out *strings.Builder) []*Node {
@@ -40,7 +56,7 @@ func (node *Node) write(out *strings.Builder) []*Node {
 		out.WriteString(":" + node.Name)
 	}
 	for key, val := range node.Keys {
-		if isSymbol(val) {
+		if NoQuote(val) {
 			out.WriteString(fmt.Sprintf(" %s:%s", key, val))
 			continue
 		}

encoder_test.go

@@ -26,3 +26,72 @@ func TestEncoder(t *testing.T) {
 		t.Fatal("before and after not the same")
 	}
 }
+
+func TestNoQuote(t *testing.T) {
+	tests := []struct {
+		value string
+		valid bool
+	}{
+		{
+			value: "one",
+			valid: true,
+		},
+		{
+			value: "-one",
+			valid: false,
+		},
+		{
+			value: "-",
+			valid: false,
+		},
+		{
+			value: "24",
+			valid: true,
+		},
+		{
+			value: "33.0e4",
+			valid: true,
+		},
+		{
+			value: "-33.0e4",
+			valid: true,
+		},
+		{
+			value: "-22",
+			valid: true,
+		},
+		{
+			value: "- 22",
+			valid: false,
+		},
+		{
+			value: "24a",
+			valid: false,
+		},
+		{
+			value: "33.0e-4",
+			valid: true,
+		},
+		{
+			value: "x-22",
+			valid: false,
+		},
+		{
+			value: "- - 33",
+			valid: false,
+		},
+		{
+			value: "go-flags",
+			valid: false,
+		},
+		{
+			value: "go flags",
+			valid: false,
+		},
+	}
+	for i, test := range tests {
+		if brief.NoQuote(test.value) != test.valid {
+			t.Errorf("%d> failed %s", i, test.value)
+		}
+	}
+}