feat: stuff

cmd/lambda/lambda.go

@@ -1,7 +1,6 @@
 package main
 
 import (
-	"errors"
 	"fmt"
 	"os"
 	"time"
@@ -26,10 +25,8 @@ func main() {
 	cli.HandleError(err)
 
 	// Parse tokens.
-	tokens, fails := tokenizer.GetTokens([]rune(input))
-	if len(fails) > 0 {
-		cli.HandleError(errors.Join(fails...))
-	}
+	tokens, err := tokenizer.GetTokens([]rune(input))
+	cli.HandleError(err)
 	logger.Info("Parsed tokens.", "tokens", tokens)
 
 	// Turn tokens into syntax tree.

pkg/iterator/iterator.go

@@ -12,8 +12,8 @@ type Iterator[T any] struct {
 }
 
 // Create a new iterator, over a set of items.
-func New[T any](items []T) Iterator[T] {
-	return Iterator[T]{data: items, index: 0}
+func New[T any](items []T) *Iterator[T] {
+	return &Iterator[T]{data: items, index: 0}
 }
 
 // Returns the current position of the iterator.
@@ -40,7 +40,7 @@ func (i Iterator[T]) Peek() (T, error) {
 
 // Moves the iterator pointer to the next item. Returns the current item. Fails
 // if there are no more items to iterate over.
-func (i *Iterator[T]) Next() (T, error) {
+func (i *Iterator[T]) Pop() (T, error) {
 	val, err := i.Peek()
 	if err != nil {
 		return val, err
@@ -49,3 +49,22 @@ func (i *Iterator[T]) Next() (T, error) {
 	i.index++
 	return val, nil
 }
+
+// Pop until the clause returns false.
+func (i *Iterator[T]) PopWhile(fn func(T) bool) []T {
+	result := []T{}
+
+	for {
+		popped, err := i.Peek()
+		if err != nil || !fn(popped) {
+			break
+		}
+
+		result = append(result, popped)
+		if _, err := i.Pop(); err != nil {
+			break
+		}
+	}
+
+	return result
+}

pkg/lambda/generate_name.go

@@ -7,12 +7,8 @@ import (
 )
 
 func GenerateFreshName(used set.Set[string]) string {
-	// Starts as '0', that is the base value of a 'uint64'.
-	var i uint64
-
-	for {
+	for i := uint64(0); ; i++ {
 		attempt := "_" + string(strconv.AppendUint(nil, i, 10))
-		i++
 
 		if !used.Has(attempt) {
 			return attempt

pkg/parser/parser.go

@@ -9,7 +9,7 @@ import (
 )
 
 func ParseExpression(i *iterator.Iterator[tokenizer.Token]) (lambda.Expression, error) {
-	token, err := i.Next()
+	token, err := i.Pop()
 	if err != nil {
 		return nil, fmt.Errorf("could not get next token: %w", err)
 	}
@@ -23,7 +23,7 @@ func ParseExpression(i *iterator.Iterator[tokenizer.Token]) (lambda.Expression,
 		atoms := []string{}
 
 		for {
-			atom, atomErr := i.Next()
+			atom, atomErr := i.Pop()
 			if atomErr != nil {
 				return nil, fmt.Errorf("could not find parameter or terminator of function: %w", atomErr)
 			} else if atom.Type == tokenizer.TokenVariable {
@@ -72,7 +72,7 @@ func ParseExpression(i *iterator.Iterator[tokenizer.Token]) (lambda.Expression,
 			args = append(args, arg)
 		}
 
-		closing, closingErr := i.Next()
+		closing, closingErr := i.Pop()
 		if closingErr != nil {
 			return nil, fmt.Errorf("could not parse call terminating parenthesis: %w", closingErr)
 		} else if closing.Type != tokenizer.TokenCloseParen {
@@ -94,6 +94,5 @@ func ParseExpression(i *iterator.Iterator[tokenizer.Token]) (lambda.Expression,
 }
 
 func GetTree(tokens []tokenizer.Token) (lambda.Expression, error) {
-	i := iterator.New(tokens)
-	return ParseExpression(&i)
+	return ParseExpression(iterator.New(tokens))
 }

pkg/tokenizer/token.go

@@ -1,17 +1,27 @@
 package tokenizer
 
+// All tokens in the pseudo-lambda language.
 type TokenType int
 
 const (
+	// Denotes the '(' token.
 	TokenOpenParen TokenType = iota
+	// Denotes the ')' token.
 	TokenCloseParen
+	// Denotes an alpha-numeric variable.
 	TokenVariable
+	// Denotes the '/' token.
 	TokenSlash
+	// Denotes the '.' token.
 	TokenDot
 )
 
+// A representation of a token in source code.
 type Token struct {
+	// Where the token begins in the source text.
 	Index int
+	// What type the token is.
 	Type TokenType
+	// The value of the token.
 	Value string
 }

pkg/tokenizer/tokenizer.go

@@ -1,95 +1,72 @@
 package tokenizer
 
 import (
+	"errors"
 	"fmt"
-	"strings"
 	"unicode"
 
 	"git.maximhutz.com/max/lambda/pkg/iterator"
 )
 
+// isVariables determines whether a rune can be a valid variable.
 func isVariable(r rune) bool {
 	return unicode.IsLetter(r) || unicode.IsNumber(r)
 }
 
+// Pulls the next token from an iterator over runes. If it cannot, it will
+// return nil. If an error occurs, it will return that.
 func getToken(i *iterator.Iterator[rune]) (*Token, error) {
+	index := i.Index()
+
 	if i.IsDone() {
 		return nil, nil
 	}
 
-	letter, err := i.Next()
+	letter, err := i.Pop()
 	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) {
+	switch {
+	case letter == '(':
+		// The opening deliminator of an application.
+		return &Token{Type: TokenOpenParen, Index: index, Value: string(letter)}, nil
+	case letter == ')':
+		// The terminator of an application.
+		return &Token{Type: TokenCloseParen, Index: index, Value: string(letter)}, nil
+	case letter == '.':
+		// The terminator of the parameters in an abstraction.
+		return &Token{Type: TokenDot, Index: index, Value: string(letter)}, nil
+	case letter == '\\':
+		// The opening deliminator of an abstraction.
+		return &Token{Type: TokenSlash, Index: index, Value: string(letter)}, nil
+	case unicode.IsSpace(letter):
+		// If there is a space character, ignore it.
 		return nil, nil
+	case isVariable(letter):
+		rest := i.PopWhile(isVariable)
+		atom := string(append([]rune{letter}, rest...))
+
+		return &Token{Index: index, Type: TokenVariable, Value: atom}, nil
 	}
 
-	// Otherwise, it is an atom.
-	atom := strings.Builder{}
-	index := i.Index()
-	for !i.IsDone() {
-		pop, err := i.Peek()
-		if err != nil || !isVariable(pop) {
-			break
-		}
-
-		atom.WriteRune(pop)
-		if _, err := i.Next(); err != nil {
-			break
-		}
-	}
-
-	return &Token{
-		Index: index,
-		Type:  TokenVariable,
-		Value: atom.String(),
-	}, nil
+	return nil, fmt.Errorf("unknown character '%v'", letter)
 }
 
-func GetTokens(input []rune) ([]Token, []error) {
+// Parses a list of runes into tokens. All error encountered are returned, as well.
+func GetTokens(input []rune) ([]Token, error) {
 	i := iterator.New(input)
 	tokens := []Token{}
-	errors := []error{}
+	errorList := []error{}
 
 	for !i.IsDone() {
-		token, err := getToken(&i)
+		token, err := getToken(i)
 		if err != nil {
-			errors = append(errors, err)
+			errorList = append(errorList, err)
 		} else if token != nil {
 			tokens = append(tokens, *token)
 		}
 	}
 
-	return tokens, errors
+	return tokens, errors.Join(errorList...)
 }