A bit more coverage + say things in README

README.md

@@ -1,4 +1,26 @@
 # argh command line parser
 
-> NOTE: much of this is lifted from
+## background
-> https://blog.gopheracademy.com/advent-2014/parsers-lexers/
+
+The Go standard library [flag](https://pkg.go.dev/flag) way of doing things has long been
+a source of frustration while implementing and maintaining the
+[urfave/cli](https://github.com/urfave/cli) library. [Many alternate parsers
+exist](https://github.com/avelino/awesome-go#standard-cli), including:
+
+- [pflag](https://github.com/spf13/pflag)
+- [argparse](https://github.com/akamensky/argparse)
+
+In addition to these other implementations, I also got some help via [this
+oldie](https://blog.gopheracademy.com/advent-2014/parsers-lexers/) and the Go standard
+library [parser](https://pkg.go.dev/go/parser).
+
+## goals
+
+- get a better understanding of the whole problem space
+- support both POSIX-y and Windows-y styles
+- build a printable/JSON-able parse tree
+- support rich error reporting
+
+<!--
+vim:tw=90
+-->

cmd/argh-example/main.go

@@ -18,7 +18,7 @@ func main() {
 	pCfg := argh.NewParserConfig()
 	pCfg.Prog = &argh.CommandConfig{
 		NValue:     argh.OneOrMoreValue,
-		ValueNames: []string{"topping"},
+		ValueNames: []string{"val"},
 		Flags: &argh.Flags{
 			Automatic: true,
 		},

scanner_test.go

@@ -0,0 +1,83 @@
+package argh
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func BenchmarkScannerPOSIXyScannerScan(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		scanner := NewScanner(strings.NewReader(strings.Join([]string{
+			"walrus",
+			"-what",
+			"--ball=awesome",
+			"--elapsed",
+			"carrot cake",
+		}, string(nul))), nil)
+		for {
+			tok, _, _ := scanner.Scan()
+			if tok == EOL {
+				break
+			}
+		}
+	}
+}
+
+func TestScannerPOSIXyScanner(t *testing.T) {
+	for _, tc := range []struct {
+		name              string
+		argv              []string
+		expectedTokens    []Token
+		expectedLiterals  []string
+		expectedPositions []Pos
+	}{
+		{
+			name: "simple",
+			argv: []string{"walrus", "-cake", "--corn-dog", "awkward"},
+			expectedTokens: []Token{
+				IDENT,
+				ARG_DELIMITER,
+				COMPOUND_SHORT_FLAG,
+				ARG_DELIMITER,
+				LONG_FLAG,
+				ARG_DELIMITER,
+				IDENT,
+				EOL,
+			},
+			expectedLiterals: []string{
+				"walrus", string(nul), "-cake", string(nul), "--corn-dog", string(nul), "awkward", "",
+			},
+			expectedPositions: []Pos{
+				6, 7, 12, 13, 23, 24, 31, 32,
+			},
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			r := require.New(t)
+
+			scanner := NewScanner(strings.NewReader(strings.Join(tc.argv, string(nul))), nil)
+
+			actualTokens := []Token{}
+			actualLiterals := []string{}
+			actualPositions := []Pos{}
+
+			for {
+				tok, lit, pos := scanner.Scan()
+
+				actualTokens = append(actualTokens, tok)
+				actualLiterals = append(actualLiterals, lit)
+				actualPositions = append(actualPositions, pos)
+
+				if tok == EOL {
+					break
+				}
+			}
+
+			r.Equal(tc.expectedTokens, actualTokens)
+			r.Equal(tc.expectedLiterals, actualLiterals)
+			r.Equal(tc.expectedPositions, actualPositions)
+		})
+	}
+}