wip: new folder structure, overhaul language

pkg/saccharine/parser.go

@@ -0,0 +1,80 @@
+package saccharine
+
+import (
+	"fmt"
+
+	"git.maximhutz.com/max/lambda/pkg/iterator"
+)
+
+func isVariableToken(t Token) bool {
+	return t.Type == TokenVariable
+}
+
+func ParseExpression(i *iterator.Iterator[Token]) (Node, error) {
+	token, err := i.Pop()
+	if err != nil {
+		return nil, fmt.Errorf("could not get next token: %w", err)
+	}
+
+	switch token.Type {
+	case TokenVariable:
+		return NewVariable(token.Value), nil
+	case TokenDot:
+		return nil, fmt.Errorf("token '.' found without a corresponding slash (column %d)", token.Index)
+	case TokenSlash:
+		tokens := i.PopWhile(isVariableToken)
+		variables := []string{}
+
+		for _, token := range tokens {
+			variables = append(variables, token.Value)
+		}
+
+		if dot, dotErr := i.Pop(); dotErr != nil {
+			return nil, fmt.Errorf("could not find parameter terminator: %w", dotErr)
+		} else if dot.Type != TokenDot {
+			return nil, fmt.Errorf("expected '.', got '%v' (column %d)", dot.Value, dot.Index)
+		}
+
+		body, bodyErr := ParseExpression(i)
+		if bodyErr != nil {
+			return nil, fmt.Errorf("could not parse function body: %w", bodyErr)
+		}
+
+		return NewAbstraction(variables, body), nil
+	case TokenOpenParen:
+		fn, fnErr := ParseExpression(i)
+		if fnErr != nil {
+			return nil, fmt.Errorf("could not parse call function: %w", fnErr)
+		}
+
+		args := []Node{}
+
+		for {
+			if next, nextErr := i.Peek(); nextErr == nil && next.Type == TokenCloseParen {
+				break
+			}
+
+			arg, argErr := ParseExpression(i)
+			if argErr != nil {
+				return nil, fmt.Errorf("could not parse call argument: %w", argErr)
+			}
+
+			args = append(args, arg)
+		}
+
+		closing, closingErr := i.Pop()
+		if closingErr != nil {
+			return nil, fmt.Errorf("could not parse call terminating parenthesis: %w", closingErr)
+		} else if closing.Type != TokenCloseParen {
+			return nil, fmt.Errorf("expected call terminating parenthesis, got '%v' (column %v)", closing.Value, closing.Index)
+		}
+
+		return NewApplication(fn, args), nil
+	}
+
+	return nil, fmt.Errorf("unexpected token '%v' (column %d)", token.Value, token.Index)
+}
+
+func GetTree(tokens []Token) (Node, error) {
+	return ParseExpression(iterator.New(tokens))
+}