feat: tokenizer

Makefile

@@ -0,0 +1,8 @@
+BINARY_NAME=lambda.exe
+
+it:
+	@ go build -o ${BINARY_NAME} ./cmd/lambda
+	@ chmod +x ${BINARY_NAME}
+
+ex1: it
+	@ ./lambda.exe "(\n.\f.\x.(f ((n f) x)) \f.\x.x)"

cmd/lambda/lambda.go

@@ -0,0 +1,24 @@
+package main
+
+import (
+	"errors"
+	"log/slog"
+	"os"
+
+	"git.maximhutz.com/max/lambda/pkg/cli"
+	"git.maximhutz.com/max/lambda/pkg/tokenizer"
+)
+
+func main() {
+	slog.Info("Using program arguments.", "args", os.Args)
+	options, err := cli.ParseOptions(os.Args[1:])
+	cli.HandleError(err)
+
+	slog.Info("Parsed CLI options.", "options", options)
+	tokens, fails := tokenizer.GetTokens([]rune(options.Input))
+	if len(fails) > 0 {
+		cli.HandleError(errors.Join(fails...))
+	}
+
+	slog.Info("Parsed tokens.", "tokens", tokens)
+}

go.mod

@@ -0,0 +1,3 @@
+module git.maximhutz.com/max/lambda
+
+go 1.25.5

pkg/cli/arguments.go

@@ -0,0 +1,28 @@
+package cli
+
+import (
+	"flag"
+	"fmt"
+	"log/slog"
+	"os"
+)
+
+type CLIOptions struct {
+	Input string
+}
+
+func ParseOptions(args []string) (*CLIOptions, error) {
+	slog.Info("Parsing CLI arguments.", "args", os.Args)
+
+	// Parse flags and arguments.
+	flag.Parse()
+
+	switch flag.NArg() {
+	case 0:
+		return nil, fmt.Errorf("No input given.")
+	case 1:
+		return &CLIOptions{Input: flag.Arg(0)}, nil
+	default:
+		return nil, fmt.Errorf("More than 1 command-line argument.")
+	}
+}

pkg/cli/exit.go

@@ -0,0 +1,15 @@
+package cli
+
+import (
+	"fmt"
+	"os"
+)
+
+func HandleError(err error) {
+	if err == nil {
+		return
+	}
+
+	fmt.Fprintln(os.Stderr, err)
+	os.Exit(1)
+}

pkg/iterator/iterator.go

@@ -0,0 +1,39 @@
+package iterator
+
+import "fmt"
+
+type Iterator[T any] struct {
+	data []T
+	index int
+}
+
+func New[T any](items []T) Iterator[T] {
+	return Iterator[T]{ data: items, index: 0 }
+}
+
+func (i Iterator[T]) Index() int {
+	return i.index
+}
+
+func (i Iterator[T]) IsDone() bool {
+	return i.index == len(i.data)
+}
+
+func (i Iterator[T]) Peek() (T, error) {
+	var null T
+
+	if i.IsDone() {
+		return null, fmt.Errorf("Iterator is exhausted.")
+	}
+
+	return i.data[i.index], nil
+}
+
+func (i *Iterator[T]) Next() (T, error) {
+	if val, err := i.Peek(); err != nil {
+		return val, err
+	} else {
+		i.index++
+		return val, nil
+	}
+}

pkg/tokenizer/token.go

@@ -0,0 +1,17 @@
+package tokenizer
+
+type TokenType int
+
+const (
+	TokenOpenParen TokenType = iota
+	TokenCloseParen
+	TokenAtom
+	TokenSlash
+	TokenDot
+)
+
+type Token struct {
+	Index int
+	Type TokenType
+	Value string
+}

pkg/tokenizer/tokenizer.go

@@ -0,0 +1,93 @@
+package tokenizer
+
+import (
+	"fmt"
+	"unicode"
+
+	"git.maximhutz.com/max/lambda/pkg/iterator"
+)
+
+func getToken(i *iterator.Iterator[rune]) (*Token, error) {
+	if i.IsDone() {
+		return nil, nil
+	}
+
+	letter, err := i.Next()
+	if err != nil {
+		return nil, fmt.Errorf("Cannot produce next token: %w", err)
+	}
+
+	// If it is an operand.
+	switch letter {
+	case '(':
+		return &Token{
+			Type: TokenOpenParen,
+			Index: i.Index(),
+			Value: string(letter),
+		}, nil
+	case ')':
+		return &Token{
+			Type: TokenCloseParen,
+			Index: i.Index(),
+			Value: string(letter),
+		}, nil
+	case '.':
+		return &Token{
+			Type: TokenDot,
+			Index: i.Index(),
+			Value: string(letter),
+		}, nil
+	case '\\':
+		return &Token{
+			Type: TokenSlash,
+			Index: i.Index(),
+			Value: string(letter),
+		}, nil
+	}
+
+	// If it is a space.
+	if unicode.IsSpace(letter) {
+		return nil, nil
+	}
+
+	// Otherwise, it is an atom.
+	atom := string(letter)
+	index := i.Index()
+	for {
+		if i.IsDone() {
+			return nil, nil
+		}
+
+		pop, err := i.Next()
+		if err != nil {
+			return nil, err
+		}
+
+		if unicode.IsSpace(pop) {
+			return &Token{
+				Index: index,
+				Type: TokenAtom,
+				Value: atom,
+			}, nil
+		}
+		
+		atom += string(pop)
+	}
+}
+
+func GetTokens(input []rune) ([]Token, []error) {
+	i := iterator.New(input)
+	tokens := []Token{}
+	errors := []error{}
+
+	for !i.IsDone() {
+		token, err := getToken(&i)
+		if err != nil {
+			errors = append(errors, err)
+		} else if token != nil {
+			tokens = append(tokens, *token)
+		}
+	}
+
+	return tokens, errors
+}